Vet Path January 2012
Getting Leukocytes to the Site of Inflammation
There is no ‘‘response’’ in either the innate or adaptive immune response unless leukocytes cross blood vessels. They do this
through the process of diapedesis, in which the leukocyte moves in ameboid fashion through tightly apposed endothelial borders
(paracellular transmigration) and in some cases through the endothelial cell itself (transcellular migration). This review summarizes
the steps leading up to diapedesis, then focuses on the molecules and mechanisms responsible for transendothelial
migration. Surprisingly, many of the same molecules and mechanisms that regulate paracellular migration also control transcellular
migration, including a major role for membrane from the recently described lateral border recycling compartment. A hypothesis
that integrates the various known mechanisms of transmigration is proposed.
Current State of Knowledge on Porcine Circovirus Type 2-Associated Lesions
Porcine circovirus type 2 (PCV2), a small single-stranded DNA virus, was initially discovered in 1998 and is highly prevalent in the
domestic pig population. Disease manifestations associated with PCV2 include postweaning multisystemic wasting disease
(PMWS), enteric disease, respiratory disease, porcine dermatitis and nephropathy syndrome (PDNS), and reproductive failure.
Although these clinical manifestations involve different organ systems, there is considerable overlap in clinical expression of
disease and presence of lesions between pigs and within herds. It is now widely accepted that PCV2 can be further subdivided
into different types, of which PCV2a and PCV2b are present worldwide and of greatest importance. This review will focus on
PCV2-associated lesions in different organ systems.
Domestic Cats Are Susceptible to Infection With Low Pathogenic Avian Influenza
Viruses From shorebirds
Domestic cats are susceptible to infection with highly pathogenic avian influenza virus H5N1, resulting in pneumonia and in some
cases, systemic spread with lesions in multiple organ systems. Recent transmission of the 2009 pandemic H1N1 influenza virus
from humans to cats also resulted in severe pneumonia in cats. Data regarding the susceptibility of cats to other influenza viruses is
minimal, especially regarding susceptibility to low pathogenic avian influenza viruses from wild birds, the reservoir host. In this
study, the authors infected 5-month-old cats using 2 different North American shorebird avian influenza viruses (H1N9 and H6N4
subtypes), 3 cats per virus, with the goal of expanding the understanding of avian influenza virus infections in this species. These
viruses replicated in inoculated cats based on virus isolation from the pharynx in 2 cats, virus isolation from the lung of 1 cat, and
antigen presence in the lung via immunohistochemistry in 2 cats. There was also seroconversion and lesions of patchy
bronchointerstitial pneumonia in all of the cats. Infection in the cats did not result in clinical disease and led to variable pharyngeal
viral shedding with only 1 of the viruses; virus was localized in the alveolar epithelium via immunohistochemistry. These findings
demonstrate the capacity of wild bird influenza viruses to infect cats, and further investigation is warranted into the pathogenesis
of these viruses in cats from both a veterinary medical and public health perspective.
Apoptosis in Bovine Viral Diarrhea Virus (BVDV)Induced Mucosal Disease
Lesions : A Histological, Immunohistological, and Virological Investigation
Cattle persistently infected with a noncytopathic Bovine viral diarrhea virus (BVDV) are at risk of developing fatal ‘‘mucosal disease’’
(MD). The authors investigated the role of various apoptosis pathways in the pathogenesis of lesions in animals suffering from MD.
Therefore, they compared the expression of caspase-3, caspase-8, caspase-9, and Bcl-2L1 (Bcl-x) in tissues of 6 BVDV-free control
animals, 7 persistently infected (PI) animals that showed no signs of MD (non-MD PI animals), and 11 animals with MD and
correlated the staining with the localization of mucosal lesions. Caspase-3 and -9 staining were markedly stronger in MD cases and
were associated with mucosal lesions, even though non-MD PI animals and negative controls also expressed caspase-9.
Conversely, caspase-8 was not elevated in any of the animals analyzed. Interestingly, Bcl-x also colocalized with mucosal lesions in
the MD cases. However, Bcl-x was similarly expressed in tissues from all 3 groups, and thus, its role in apoptosis needs to be
clarified. This study clearly illustrates ex vivo that the activation of the intrinsic, but not the extrinsic, apoptosis pathway is a key
element in the pathogenesis of MD lesions observed in cattle persistently infected with BVDV. However, whether direct induction of
apoptosis in infected cells or indirect effects induced by the virus are responsible for the lesions observed remains to be
established.
An Ocular Infection Model Using Suckling Hamsters Inoculated With Equine
Herpesvirus 9 (EHV-9) : Kinetics of the Virus and Time-Course Pathogenesis of
EHV-9 Induced Encephalitis via the Eyes
By using a new member of the neurotropic equine herpesviruses, EHV-9, which induced encephalitis in various species via various
routes, an ocular infection model was developed in suckling hamsters. The suckling hamsters were inoculated with EHV-9 via
the conjunctival route and were sacrificed after 6, 12, 24, 36, 48, 72, 96, 120, and 144 hours (h) post inoculation (PI). Three
horizontal sections of the brains, including the eyes and cranial cavity, were examined histologically to assess the viral kinetics and
time-course neuropathological alterations using a panoramic view. At 6 to 24 h PI, there were various degrees of necrosis in the
conjunctival epithelial cells, as well as frequent mononuclear cell infiltrations in the lamina propria and the tarsus of the eyelid, and
Vet Path January 2012
frequent myositis of the eyelid muscles. At 96 h PI, encephalitis was observed in the brainstem at the level of the pons and
cerebellum. EHV-9 antigen immunoreactivity was detected in the macrophages circulating in the eyelid and around the fine nerve
endings supplying the eyelid, the nerves of the extraocular muscles, and the lacrimal glands from 6 h to 144 h PI. At 96 h PI, the
viral antigen immunoreactivity was detected in the brainstem at the level of the pons and cerebellum. These results suggest that
EHV-9 invaded the brain via the trigeminal nerve in addition to the abducent, oculomotor, and facial nerves. This conjunctival
EHV-9 suckling hamster model may be useful in assessing the neuronal spread of neuropathogenic viruses via the eyes to the
brain.
Cryptogenic Organizing Pneumonia in Tomm5/Mice
Almost all mitochondrial proteins are encoded in the nuclear DNA and synthesized in the cytosol as pre-proteins. There is a
protein translocase located in the mitochondrial outer membrane that transports mitochondrial pre-proteins into mitochondria.
The central component of this translocase of the outer mitochondrial membrane (TOMM) complex is TOMM40, and TOMM5 is
one of three small subunits associated with TOMM40. Translocase of outer mitochondrial membrane 5 homolog (Tomm5–/–)
knockout mice demonstrated an unexpected lung-specific phenotype characterized by widespread intra-alveolar fibrosis.
Although TOMM5-deficient mice tested normal in a very broad range of phenotyping assays, they displayed histopathological
lesions in the lung that were consistent with those reported in humans with cryptogenic organizing pneumonia (COP), which
is also known as bronchiolitis obliterans organizing pneumonia (BOOP). The lesions had a patchy distribution in the lung and were
characterized by the presence of intraluminal fibrogenic buds consisting of fibroblasts and myofibroblasts embedded in a loose
connective tissue matrix that occupied the lumina of alveoli and alveolar ducts, with preservation of underlying alveolar architecture.
In addition to macrophages, which were numerous in affected and surrounding alveoli, eosinophils comprised the most common
and widespread inflammatory cell. Taken together, the findings in Tomm5–/– mice provide yet another example of the value of
histopathology as a baseline assay in high-throughput phenotyping systems.
Immunophenotypical Characterization of Macrophages in Rat Bleomycin-Induced
Scleroderma
Scleroderma is a skin disorder characterized by persistent fibrosis. Macrophage properties influencing cutaneous fibrogenesis
remain to be fully elucidated. In this rat (F344 rats) model of scleroderma, at 1, 2, 3, and 4 weeks after initiation of daily
subcutaneous injections of bleomycin (BLM; 100 ml of 1 mg/ml daily), skin samples were collected for histological and
immunohistochemical evaluations. Immunohistochemically, the numbers of cells reacting to ED1 (anti-CD68; phagocytic activity)
and ED2 (anti-CD163; inflammatory factor production) began to increase at week 1, peaked at week 2, and decreased thereafter. In
contrast, the increased number of cells reacting to OX6 (anti–MHC class II molecules) was seen from week 2 and remained
elevated until week 4. a– Smooth muscle actin–positive myofibroblasts were increased for 4 weeks. Double labeling revealed that
galectin-3, a regulator of fibrogenic factor TGF-b1, was expressed in CD68þ, CD163þ, andMHCclass IIþ macrophages and
myofibroblasts. mRNA expression of TGF-b1, as well as MCP-1 and CSF-1 (both macrophage function modulators), were
significantly elevated at weeks 1 to 4. This study shows that the increased number of macrophages with heterogeneous
immunophenotypes, which might be induced by MCP-1 and CSF-1, could participate in the sclerotic lesion formation, presumably
through increased fibrogenic factors such as galectin-3 and TGF-b1; the data may provide useful information to understand the
pathogenesis of the human scleroderma condition.
Two Hundred Three Cases of Equine Lymphoma Classified According to the
World Health Organization (WHO) Classification Criteria
Lymphoma is the most common malignant neoplasm in the horse. Single case reports and small retrospective studies of equine
lymphomas are reported infrequently in the literature. A wide range of clinical presentations, tumor subtypes, and outcomes have
been described, and the diversity of the results demonstrates the need to better define lymphomas in horses. As part of an
initiative of the Veterinary Cooperative Oncology Group, 203 cases of equine lymphoma have been gathered from 8 institutions.
Hematoxylin and eosin slides from each case were reviewed and 187 cases were immunophenotyped and categorized according
to the World Health Organization classification system. Data regarding signalment, clinical presentation, and tumor topography
were also examined. Ages ranged from 2 months to 31 years (mean, 10.7 years). Twenty-four breeds were represented;
Quarterhorses were the most common breed (n ¼ 55), followed by Thoroughbreds (n ¼ 33) and Standardbreds (n ¼ 30).
Lymphomas were categorized into 13 anatomic sites. Multicentric lymphomas were common (n ¼ 83), as were skin (n ¼ 38) and
gastrointestinal tract (n ¼ 24). A total of 14 lymphoma subtypes were identified. T-cell–rich large B-cell lymphomas were the most
common subtype, diagnosed in 87 horses. Peripheral T-cell lymphomas (n ¼ 45) and diffuse large B-cell lymphomas (n ¼ 26) were
also frequently diagnosed.
Prognostic Value of Histological Grading in Noninflammatory Canine Mammary
Carcinomas in a Prospective Study With Two-Year Follow-Up : Relationship With
Clinical and Histological Characteristics
In this prospective study, a canine-adapted histological grading method was compared with histopathological and clinical
characteristics and was evaluated as a prognostic indicator in canine mammary carcinomas (CMCs). Recruited dogs with at least 1
malignant mammary tumor (n ¼ 65) were clinically evaluated, surgically treated, and followed up (minimum follow-up 28 months,
maximum 38 months). Histopathological diagnoses were performed according to Goldschmidt et al (2011). Tumors were graded
as grade I (29/65), grade II (19/65), and grade III (17/65). The tumor size, clinical stage, histological diagnosis, presence/absence of
Vet Path January 2012
myoepithelial proliferation, and regional lymph node metastases at diagnosis were significantly associated with histological grade.
The histological grade, age, clinical stage, tumor subtype group, and lymph node metastases at time of diagnosis were significantly
associated with the development of recurrences and/or metastases, cancer-associated death, and survival times (disease-free
survival and overall survival) in univariate analyses. A subdivision of clinical stage I (T1N0M0) into stages IA and IB was proposed
in terms of prognosis. The clinical stage, histological grade, and spay status were selected as independent prognostic variables
(multivariate analyses) with disease-free survival as the dependent variable. When overall survival was evaluated as a dependent
variable, clinical stage and histological grade were selected as the independent covariates. This grading system is a useful
prognostic tool, facilitates histological interpretation, and offers uniform criteria for veterinary pathologists. Comparative studies on
CMCs performed in different countries should take into account possible changes in the prognoses due to different proportions
of spayed females among the selected dog population.
Immunohistochemical Characterization of Feline Mast Cell Tumors
Expression of histamine, serotonin, and KIT was evaluated in 61 archived feline mast cell tumors (MCTs) from the skin (n ¼ 29),
spleen (n ¼ 17), and gastrointestinal (GI) tract (n ¼ 15) using immunohistochemistry. Twenty-eight percent of cutaneous MCTs,
18% of splenic MCTs, and 53% of GI MCTs displayed histamine immunoreactivity. Serotonin immunoreactivity was detected in 3
GI and 1 cutaneous MCT. Sixty-nine percent of cutaneous MCTs, 35% of splenic MCTs, and 33% of GI MCTs were positive for
KIT. Expression of these biogenic amines and KIT was less common than expected. Results of this study suggest heterogeneity in
feline MCTs based on anatomic location. Further studies are needed to explain the significance of these differences.
Expression of Ki67, BCL-2, and COX-2 in Canine Cutaneous Mast Cell Tumors :
Association With Grading and Prognosis
The expression of Ki67, BCL-2, and COX-2 was investigated in 53 canine cutaneous mast cell tumors (MCTs) by
immunohistochemistry and quantitative real time polymerase chain reaction (qPCR) to evaluate their prognostic significance
and the association with the histologic grading and the mitotic index (MI). MCTs were graded according to the
Patnaik grading system and the novel 2-tier grading system proposed by Kiupel. The numbers of mitotic figures/10 highpower
fields (MI) were counted. Both grading systems were significantly associated with prognosis. The Patnaik grading
was of limited prognostic value for grade 2 MCTs, with 23% being associated with mortality. The concordance among
pathologists was strongly improved by the application of the 2-tier grading system, and 71% of high-grade MCTs were
associated with a high mortality rate. MI and Ki67 protein expression were significantly associated with grading and
survival. No significant association between BCL-2 protein expression and either grading system or health status was
observed. BCL-2 mRNA expression was significantly higher in grade 2 than in grade 1 MCTs, while no statistically significant
differences were detected between low- and high-grade MCTs. The increased BCL-2 mRNA level was significantly
associated with increased mortality rate. The COX-2 protein expression was detected in 78% of the MCTs investigated.
However, neither association with the tumor grade nor with the health status was observed. COX-2 mRNA was significantly
up-regulated in MCTs compared to surgical margins and control skin tissue, but it was neither associated with
tumor grade nor with survival.
Nonlesions, Unusual Cell Types, and Postmortem Artifacts in the Central Nervous
System of Domestic Animals
In the central nervous system (CNS) of domestic animals, numerous specialized normal structures, unusual cell types, findings of
uncertain or no significance, artifacts, and various postmortem alterations can be observed. They may cause confusion for
inexperienced pathologists and those not specialized in neuropathology, leading to misinterpretations and wrong diagnoses.
Alternatively, changes may mask underlying neuropathological processes. ‘‘Specialized structures’’ comprising the hippocampus
and the circumventricular organs, including the vascular organ of the lamina terminalis, subfornical organ, subcommissural organ,
pineal gland, median eminence/neurohypophyseal complex, choroid plexus, and area postrema, are displayed. Unusual cell types,
including cerebellar external germinal cells, CNS progenitor cells, and Kolmer cells, are presented. In addition, some newly
recognized cell types as of yet incompletely understood significance and functionality, such as synantocytes and aldynoglia, are
introduced and described. Unusual reactive astrocytes in cats, central chromatolysis, neuronal vacuolation, spheroids, spongiosis,
satellitosis, melanosis, neuromelanin, lipofuscin, polyglucosan bodies, and psammoma bodies may represent incidental findings of
uncertain or no significance and should not be confused with significant microscopic changes. Auto- and heterolysis as well as
handling and histotechnological processing may cause postmortem morphological changes of the CNS, including vacuolization,
cerebellar conglutination, dark neurons, Buscaino bodies, freezing, and shrinkage artifacts, all of which have to be differentiated
from genuine lesions. Postmortem invasion of micro-organisms should not be confused with intravital infections. Awareness of
these different changes and their recognition are a prerequisite for identifying genuine lesions and may help to formulate a
professional morphological and etiological diagnosis.
Preliminary Findings of a Previously Unrecognized Porcine Primary
Immunodeficiency Disorder
Weaned pigs from a line bred for increased feed efficiency were enrolled in a study of the role of host genes in the response to
infection with Porcine Reproductive and Respiratory Syndrome Virus (PRRSV). Four of the pigs were euthanatized early in the
study due to weight loss with illness and poor body condition; 2 pigs before PRRSV infection and the other 2 pigs approximately 2
weeks after virus inoculation. The 2 inoculated pigs failed to produce PRRSV-specific antibodies. Gross findings included
pneumonia, absence of a detectable thymus, and small secondary lymphoid tissues. Histologically, lymph nodes, spleen, tonsils,
and Peyer’s patches were sparsely cellular with decreased to absent T and B lymphocytes.
Vet Path January 2012
Histomorphometry of Feline Chronic Kidney Disease and Correlation With
Markers of Renal Dysfunction
Chronic kidney disease is common in geriatric cats, but most cases have nonspecific renal lesions, and few studies have correlated
these lesions with clinicopathological markers of renal dysfunction. The aim of this study was to identify the lesions best
correlated with renal function and likely mediators of disease progression in cats with chronic kidney disease. Cats were
recruited through 2 first-opinion practices between 1992 and 2010. When postmortem examinations were authorized,
renal tissues were preserved in formalin. Sections were evaluated by a pathologist masked to all clinicopathological data.
They were scored semiquantitatively for the severity of glomerulosclerosis, interstitial inflammation, and fibrosis. Glomerular
volume was measured using image analysis; the percentage of glomeruli that were obsolescent was recorded. Sections
were assessed for hyperplastic arteriolosclerosis and tubular mineralization. Kidneys from 80 cats with plasma biochemical data
from the last 2 months of life were included in the study. Multivariable linear regression (P < .05) was used to assess the association
of lesions with clinicopathological data obtained close to death. Interstitial fibrosis was the lesion best correlated with the
severity of azotemia, hyperphosphatemia, and anemia. Proteinuria was associated with interstitial fibrosis and glomerular
hypertrophy, whereas higher time-averaged systolic blood pressure was associated with glomerulosclerosis and hyperplastic
arteriolosclerosis.
Perineal Choristoma and Atresia Ani in 2 Female Holstein Friesian Calves
Atresia ani, a congenital anomaly of the anus, can be associated with other types of malformation. Two female Holstein Friesian
calves had imperforate anus, rectovaginal fistula, and perineal choristomas. In one case, the choristoma was composed of
mature adipose and fibrous tissue with nephrogenic rests. In the other calf, the choristoma consisted of fragments of trabecular
bone coated by cartilage and containing marrow, mixed with mature adipose and fibrous tissue, striated muscle fibers, nerves,
and vessels. This combination of malformations resembles the association of anorectal malformations and perineal masses in
children.
Integrated Histopathological and Urinary Metabonomic Investigation of the
Pathogenesis of Microcystin-LR Toxicosis
Patterns of change of endogenous metabolites may closely reflect systemic and organ-specific toxic changes. The authors
examined the metabolic effects of the cyanobacterial (blue-green algal) toxin microcystin-LR by 1H-nuclear magnetic resonance
(NMR) analysis of urinary endogenous metabolites. Rats were treated with a single sublethal dose, either 20 or 80 mg/kg
intraperitoneally, and sacrificed at 2 or 7 days post dosing. Changes in the high-dose, 2-day sacrifice group included centrilobular
hepatic necrosis and congestion, accompanied in some animals by regeneration and neovascularization. By 7 days, animals had
recovered, the necrotizing process had ended, and the centrilobular areas had been replaced by regenerative, usually hypertrophic
hepatocytes. There was considerable interanimal variation in the histologic process and severity, which correlated with the changes
in patterns of endogenous metabolites in the urine, thus providing additional validation of the biomarker and biochemical changes.
Similarity of the shape of the metabolic trajectories suggests that the mechanisms of toxic effects and recovery are similar among
the individual animals, albeit that the magnitude and timing are different for the individual animals. Initial decreases in urinary citrate,
2-oxoglutarate, succinate, and hippurate concentrations were accompanied by a temporary increase in betaine and taurine, then
creatine from 24 to 48 hours. Further changes were an increase in guanidinoacetate, dimethylglycine, urocanic acid, and bile acids.
As a tool, urine can be repeatedly and noninvasively sampled and metabonomics utilized to study the onset and recovery after
toxicity, thus identifying time points of maximal effect. This can help to employ histopathological examination in a guided and
effective fashion.
Occlusive Fungal Tracheitis in 4 Captive Bottlenose Dolphins (Tursiops
truncatus)
Respiratory disease is common in dolphins, primarily affecting pulmonary parenchyma and sparing large airways. Over a 10-year
period, 4 captive adult bottlenose dolphins succumbed to chronic, progressive respiratory disease with atypical recurrent upper
respiratory signs. All dolphins had severe, segmental to circumferential fibrosing tracheitis that decreased luminal diameter.
Histologically, tracheal cartilage, submucosa, and mucosa were distorted and replaced by extensive fibrosis and pyogranulomatous
inflammation centered on fungal hyphae. In 3 of 4 cases, hyphae were morphologically compatible with Aspergillus spp and
confirmed by culture in 2 cases. Amplification of fungal DNA from tracheal tissue was successful in one case, and sequences had
approximately 98% homology to Aspergillus fumigatus. The remaining case had fungi compatible with zygomycetes; however,
culture and polymerase chain reaction were unsuccessful. Lesions were evaluated immunohistochemically using antibodies
specific to Aspergillus spp. Aspergillus-like hyphae labeled positively, while presumed zygomycetes did not. These cases represent
a novel manifestation of respiratory mycoses in bottlenose dolphins.
Hepatic Encephalopathy Associated With Hepatic Lipidosis in Llamas (Lama
glama)
Hepatic encephalopathy has been listed as a differential for llamas displaying neurologic signs, but it has not been
histopathologically described. This report details the neurologic histopathologic findings associated with 3 cases of hepatic lipidosis
with concurrent neurologic signs and compares them to 3 cases of hepatic lipidosis in the absence of neurologic signs and 3 cases
without hepatic lipidosis. Brain from all 3 llamas displaying neurologic signs contained Alzheimer type II cells, which were not
detected in either subset of llamas without neurologic signs. Astrocytic immunohistochemical staining intensity for glial fibrillary
acid protein was decreased in llamas with neurologic signs as compared to 2 of 3 llamas with hepatic lipidosis and without
neurologic signs and to 2 of 3 llamas without hepatic lipidosis. Immunohistochemical staining for S100 did not vary between
groups. These findings suggest that hepatic encephalopathy may be associated with hepatic lipidosis in llamas.
Vet Path January 2012
Purkinje Cell Heterotopy With Cerebellar Hypoplasia in Two Free-Living American
Kestrels (Falco sparverius )
Two wild fledgling kestrels exhibited lack of motor coordination, postural reaction deficits, and abnormal propioception. At
necropsy, the cerebellum and brainstem were markedly underdeveloped. Microscopically, there was Purkinje cells heterotopy,
abnormal circuitry, and hypoplasia with defective foliation. Heterotopic neurons were identified as immature Purkinje cells by
their size, location, immunoreactivity for calbindin D-28 K, and ultrastructural features. The authors suggest that this cerebellar
abnormality was likely due to a disruption of molecular mechanisms that dictate Purkinje cell migration, placement, and
maturation in early embryonic development. The etiology of this condition remains undetermined. Congenital central nervous
system disorders have rarely been reported in birds.
Naturally Acquired Visceral Leishmaniosis in a Captive Bennett's Wallaby
(Macropus rufogriseus rufogriseus )
A high prevalence of leishmaniosis has been reported from an increasing number of domestic and wild mammals around the
world. In Australian macropods, Leishmania spp infection has been occasionally described in its cutaneous form only. The purpose
of this report is to present a case of fatal visceral leishmaniosis in a captive Bennett’s wallaby in Madrid, Spain, which was
investigated by detailed macroscopic, histologic, and immunohistochemical examinations.
Weigners FixativeAn Alternative to Formalin Fixation for Histology With
Improved Preservation of Nucleic Acids
Formalin fixation and paraffin embedding (FFPE) is the standard method for tissue storage in histopathology. However, FFPE has
disadvantages in terms of user health, environment, and nucleic acid integrity. Weigners fixative has been suggested as an
alternative for embalming cadavers in human and veterinary anatomy. The present study tested the applicability of Weigners for
histology and immunohistochemistry and the preservation of nucleic acids. To this end, a set of organs was fixed for 2 days and up
to 6 months in Weigners (WFPE) or formalin. WFPE tissues from the skin, brain, lymphatic tissues, liver, and muscle had good
morphologic preservation, comparable to formalin fixation. The quality of kidney and lung samples was inferior to FFPE material
due to less accentuated nuclear staining and retention of proteinaceous interstitial fluids. Azan, Turnbull blue, toluidin, and
immunohistochemical stainings for CD79a, cytokeratin, vimentin, and von Willebrand factor led to comparable results with both
fixates. Of note, immunohistochemical detection of CD3 was possible after 6 months in WFPE but not in FFPE tissues. mRNA,
miRNA, and DNA from WFPE tissues had superior quality and allowed for amplification of miRNA, 400-bp-long mRNA, and
1000-bp-long DNA fragments after 6 months of fixation in WFPE. In summary, Weigners fixative is a nonhazardous alternative
to formalin, which provides a good morphologic preservation of most organs, a similar sensitivity for protein detection, and a
superior preservation of nucleic acids. Weigners may therefore be a promising alternative to cryopreservation and may be
embraced by people affected by formalin allergies.
Novel Genital Alphapapillomaviruses in Baboons (Papio hamadryas Anubis) With
Cervical Dysplasia
Genital Alphapapillomavirus (aPV) infections are one of the most common sexually transmitted human infections worldwide.
Women infected with the highly oncogenic genital human papillomavirus (HPV) types 16 and 18 are at high risk for development
of cervical cancer. Related oncogenic aPVs exist in rhesus and cynomolgus macaques. Here the authors identified 3 novel genital
aPV types (PhPV1, PhPV2, PhPV3) by PCR in cervical samples from 6 of 15 (40%) wild-caught female Kenyan olive baboons
(Papio hamadryas anubis). Eleven baboons had koilocytes in the cervix and vagina. Three baboons had dysplastic proliferative
changes consistent with cervical squamous intraepithelial neoplasia (CIN). In 2 baboons with PCR-confirmed PhPV1, 1 had
moderate (CIN2, n ¼ 1) and 1 had low-grade (CIN1, n ¼ 1) dysplasia. In 2 baboons with PCR-confirmed PhPV2, 1 had low-grade
(CIN1, n ¼ 1) dysplasia and the other had only koilocytes. Two baboons with PCR-confirmed PhPV3 had koilocytes only. PhPV1
and PhPV2 were closely related to oncogenic macaque and human aPVs. These findings suggest that aPV-infected baboons may
be useful animal models for the pathogenesis, treatment, and prophylaxis of genital aPV neoplasia. Additionally, this discovery
suggests that genital aPVs with oncogenic potential may infect a wider spectrum of non-human primate species than previously
thought.
Use of Electron Microscopy to Classify Canine Perivascular Wall Tumors
The histologic classification of canine perivascular wall tumors (PWTs) is controversial. Many PWTs are still classified as
hemangiopericytomas (HEPs), and the distinction from peripheral nerve sheath tumors (PNSTs) is still under debate. A recent
histologic classification of canine soft tissue sarcomas included most histologic types of PWT but omitted those that were termed
undifferentiated. Twelve cases of undifferentiated canine PWTs were evaluated by transmission electron microscopy. The
ultrastructural findings supported a perivascular wall origin for all cases with 4 categories of differentiation: myopericytic (n ¼ 4),
myofibroblastic (n ¼ 1), fibroblastic (n ¼ 2), and undifferentiated (n ¼ 5). A PNST was considered unlikely in each case based on
immunohistochemical expression of desmin and/or the lack of typical ultrastructural features, such as basal lamina. Electron
microscopy was pivotal for the subclassification of canine PWTs, and the results support the hypothesis that canine PWTs
represent a continuum paralleling the phenotypic plasticity of vascular mural cells. The hypothesis that a subgroup of PWTs could
arise from a pluripotent mesenchymal perivascular wall cell was also considered and may explain the diverse differentiation of
canine PWTs.
Vet Path January 2012
Cutaneous Mast Cell Tumor With Epitheliotropism in 3 Dogs
Epitheliotropism is an important diagnostic feature of cutaneous epitheliotropic lymphoma and canine cutaneous histiocytoma;
however, although noted in certain feline mastocytic diseases, it has not been considered a feature of canine cutaneous mast cell
tumor. In this study, 3 canine cutaneous mast cell tumors had epitheliotropic invasion of neoplastic mast cells into the epidermis
and follicular epithelium. This unusual histologic finding was characterized by infiltrates of individual and clusters of neoplastic mast
cells in the stratum basale and stratum spinosum. The mast cell origin of these cells was documented by demonstration of
metachromasia with Giemsa stain and positive immunoreactivity to KIT protein. On the basis of these findings, mast cell tumors
should be included in the differential diagnosis for canine cutaneous round cell neoplasms that infiltrate the epidermis.
Immunohistochemical and Biochemical Evidence of Ameloblastic Origin of
Amyloid-Producing Odontogenic Tumors in Cats
Amyloid-producing odontogenic tumors (APOT) are rare, and in cats, the histogenesis of the amyloid remains undetermined. In
the present study, APOTs in 3 cats were characterized by immunohistochemistry, and the amyloid components analyzed using
tandem mass spectrometry. Antiameloblastin antibodies labeled both neoplastic epithelial cells and amyloid in all cases. Neoplastic
epithelial cells had strong, diffuse immunoreactivity to antibodies against cytokeratin AE1/AE3, cytokeratin 14, and cytokeratin 19
in all cases and focal immunoreactivity to nerve growth factor receptor antibodies in 2 of 3 cases. Amyloid and some tumor stromal
cells were weakly positive for laminin. Calretinin, amelogenin, S100, and glial fibrillary acidic protein antibodies did not label
neoplastic epithelial cells or amyloid. Extracted amyloid peptide sequences were compared to the porcine database because the
cat genome is not yet complete. Based on this comparison, 1 identical ameloblastin peptide was detected in each tumor. These
results suggest that feline APOTs and the amyloid they produce are of ameloblastic lineage.
Ventricular and Extraventricular Ependymal Tumors in 18 Cats
Ependymal tumors are reported rarely in domestic animals. The aims of this study were to examine the clinical and pathologic
features of ventricular and extraventricular ependymomas and subependymomas in 18 domestic cats examined between 1978 and
2011. Parameters examined included age, sex, breed, clinical signs, and macroscopic and histopathologic features. The mean age
of affected cats was 9 years, 4 months; median age, 8.5 years. There were 8 female and 4 male cats, and 6 cats for which sex was
not recorded. Breeds included 10 domestic shorthaired, 2 domestic longhaired, 1 Persian, and 1 Siamese. Clinical signs included
altered mentation or behavior, seizures, circling, propulsive gait, generalized discomfort, and loss of condition. The tumors often
formed intraventricular masses and usually arose from the lining of the lateral or third ventricles, followed by the fourth ventricle,
mesencephalic aqueduct, and spinal cord central canal. Three tumors were extraventricular, forming masses within the cerebrum
and adjacent subarachnoid space. Histologically, 15 tumors were classified as variants of ependymomas (classic, papillary,
tanycytic, or clear cell) and 3 as subependymomas. Tumors were generally well demarcated; however, 6 ependymomas focally or
extensively infiltrated the adjacent neural parenchyma. Characteristic perivascular pseudorosettes were observed in all
ependymomas; true rosettes were less common. Some tumors had areas of necrosis, mineralization, cholesterol clefts, and/or
hemorrhage. This cohort study of feline ependymal tumors includes subependymoma and primary extraventricular ependymoma,
variants not previously described in the veterinary literature but well recognized in humans.
Granulomatous Typhlocolitis, Lymphangitis, and Lymphadenitis in a Horse
Infected With Listeria monocytogenes , Salmonella Typhimurium, and
Cyathostomes
A 15-year-old American Quarter horse mare was euthanized because of poor response to therapy for severe diarrhea. Significant
gross findings were limited to the large intestines. The walls of the cecum and colon were thickened with widely scattered nodules
in the mucosa and submucosa that extended into the enlarged colic lymph nodes. Microscopically, there was severe granulomatous
typhlocolitis, lymphangitis, and lymphadenitis, with many intralesional Gram-positive, non-acid-fast coccobacilli and few
cyathostomes. Intralesional bacteria were immunohistochemically and polymerase chain reaction (PCR) assay positive for Listeria
monocytogenes. Concurrent infection with Salmonella enterica serovar Typhimurium was detected by PCR and culture. Infection
with L. monocytogenes in horses is rare, and coinfection with Salmonella and small strongyles probably contributed to the
development of granulomatous typhlocolitis.
Green Algal Peritonitis in 2 Cows
Peritonitis due to infections with green algae was diagnosed at slaughter (in Texas and South Dakota) in 2 cows. One cow also
had a generalized lymphadenitis. The intralesional green algae were histologically similar to those previously associated with
bovine lymphadenitis. Amplified and sequenced algal ITS2 genes had higher homology with the genus Scenedesmus than with
Chlorella.
Otitis Interna Induced by Cryptococcus neoformans var. grubii in a Cat
Cryptococcus neoformans var. grubii was identified at necropsy in a case of bilateral otitis interna in a 7-year-old, female, domestic
shorthair cat with a 9-day history of acute onset of vestibular disease. Gross examination, including that of the middle and inner
ears, was unremarkable. Histologically, the auricular vestibuli, cochleae, and semicircular canals were bilaterally affected by
granulomatous inflammation with extracellular and intrahistiocytic yeasts. The yeasts and associated inflammation obstructed and
disrupted perilymphatic and endolymphatic spaces of the inner ears. Disruption of the saccular and utricular maculae, cristae
ampularis, and organ of Corti, as well as changes in the endolymphatic and perilymphatic fluids, probably impaired the vestibular
and auditory functions of this cat. The route of infection was most likely hematogenous.
Vet Path January 2012
Age-Associated Cartilage Degeneration of the Canine Humeral Head
The goal of this study was to determine if cartilage lesions of the humeral head in adult dogs are the consequence of
osteochondrosis dissecans or degenerative joint disease. A gross and histologic survey was performed of humeral head cartilage
lesions of 155 dogs ranging in age from 1 week to 19 years. The humeral head and cartilage lesion size were measured for each
dog. Cartilage lesions were classified as fibrillation, fissures, erosion, and/or eburnation. The area of each lesion was multiplied by a
severity score (fibrillation and fissures 1, erosion 2, and eburnation 3) to create a combined score for each humeral head.
Correlations between this combined lesion score and age, humeral head size, body weight, and body condition score were
assessed using a Bonferroni-corrected alpha of .01. Twenty-six humeral heads were also evaluated histologically. Of the 155 dogs,
80 (52%) had gross lesions of the articular cartilage. The presence and severity of the articular cartilage lesions were positively
correlated with age, humeral head size, body weight, and body condition score. The average age of dogs with cartilage lesions was
8.8 years, and 77/105 (74%) of adult dogs had cartilage lesions. Fifty dogs were 3 years of age or younger; 3 of those had cartilage
lesions, 1 of which was osteochondrosis. These data indicate that cartilage erosion of the caudal humeral head in dogs is a common
degenerative lesion acquired in adult large breed dogs; osteochondrosis dissecans does not precede the lesion in the vast
majority of cases.
The Presence of p16CDKN2A Protein Immunostaining Within Feline Nasal
Planum Squamous Cell Carcinomas Is Associated With an Increased Survival
Time and the Presence of Papillomaviral DNA
In humans, oral SCCs are either caused by papillomavirus (PV) infection or by other carcinogens such as tobacco. As these 2
groups of SCCs have different causes they also have different clinical behaviors. Immunostaining using anti-p16CDKN2A protein
(p16) antibodies is used to indicate a PV etiology in human oral SCCs and p16-positive SCCs have a more favorable prognosis. The
present study investigated whether p16 immunostaining within feline nasal planum SCCs was similarly associated with the
presence of PV DNA and with a longer survival time. Intense p16 immunostaining was visible in 32 of 51 (63%) SCCs. In 30 cats
with nonexcised SCCs, cats with p16-positive neoplasms had a longer estimated mean survival time (643 days) than cats with
p16-negative SCCs (217 days, P ¼ .013). Papillomavirus DNA was amplified more frequently from p16-positive nasal planum SCCs
(28 of 32) than p16-negative SCCs (5 of 19, P < .001). The different survival times in cats with p16-positive and p16-negative SCCs
suggests that p16 could be a useful prognostic indicator in these common feline cancers. As the clinical behavior of the SCCs can
be subdivided using p16 immunostaining, the 2 groups of SCCs may be caused by different factors, supporting a PV etiology in a
proportion of feline nasal planum SCCs.
Alteration in E-Cadherin/-Catenin Expression in Canine Melanotic Tumors
b-Catenin, encoded by the ctnnb1 gene, plays a critical role in intercellular adhesion, and its altered expression has been
implicated in tumor progression in humans and animals. The aims of this study were to examine the alterations in b-catenin
expression in canine melanoma as well as the causes of these changes (eg, E-cadherin or exon 3 mutations) and to compare
identified changes between skin and oralmelanomas. Forty-two primary canine skin and oralmelanoma tissue samples were used
in the study. The expression levels of ctnnb1 and the levels of E-cadherin/b-catenin complex in the tissues were determined by
semiquantitative RT-PCR and immunohistochemistry, respectively. The mutational status of b-catenin exon 3 was examined by
DNA sequencing. RT-PCR revealed higher levels of ctnnb1 expression in oral melanoma tissues compared with normal
melanocytes, irrespective of sex or histopathological appearance of the tissue (ie, amelanotic vs melanotic). Immunohistochemistry
revealed simultaneous loss of membrane E-cadherin/b-catenin complex and cytoplasmic accumulation of both proteins in 37
cases (84%). Intranuclear b-catenin was also detected in all tissues with reduced membrane b-catenin expression. In mutational
analyses, one amelanotic oral melanoma showed 13 single nucleotide polymorphisms (SNPs); however, after protein translation,
all the SNPs were silent mutations. The present study demonstrates that dysregulation of E-cadherin/b-catenin complexes is
involved in both types of canine melanotic tumors and that the disruption of E-cadherin/b-catenin complexes and increased
b-catenin may induce tumor progression and malignancy.
Hepatosplenic and Hepatocytotropic T-Cell Lymphoma : Two Distinct Types of TCell Lymphoma in Dogs
The clinical, clinicopathologic, and pathological findings of 9 dogs with T-cell lymphoma that involved the liver in the absence of
peripheral lymphadenopathy were assessed. Seven dogs had hepatosplenic T-cell lymphoma (HS-TCL). Dogs with HS-TCL
presented with hepato- and/or splenomegaly, regenerative anemia, thrombocytopenia, and hypoproteinemia. The clinical course
was rapidly progressive with all dogs but 1 dead within 24 days of initial presentation. Neoplastic lymphocytes were centered on
hepatic and splenic sinusoids and had a CD3þ (5/7), TCRab– (5/5), TCRgdþ (3/5), CD11dþ (6/7), granzyme Bþ (5/7)
immunophenotype. Bone marrow and lungs were consistently but variably involved. These findings closely resemble the human
disease and support the classification of HS-TCL as a distinct World Health Organization entity in dogs. The remaining 2 dogs
markedly differed in the pattern of hepatic involvement by neoplastic lymphocytes, which were not confined to hepatic sinusoids but
invaded hepatic cords. In addition, neoplastic cells had a CD11d– immunophenotype, and clinicopathologic data indicated marked
cholestasis and mild to absent anemia. Based on the distinct tropism of neoplastic lymphocytes for hepatocytes, the name
hepatocytotropic T-cell lymphoma (HC-TCL) is proposed. Given the histomorphologic, clinicopathologic, and immunophenotypic
differences, HC-TCL likely represents a separate biological entity rather than a histomorphologic variant of HS-TCL.
Mycoplasma CorogypsiAssociated Polyarthritis and Tenosynovitis in Black
Vultures (Coragyps atratus)
Three wild American black vultures (Coragyps atratus) were presented to rehabilitation centers with swelling of multiple joints,
Vet Path January 2012
including elbows, stifles, hocks, and carpal joints, and of the gastrocnemius tendons. Cytological examination of the joint fluid
exudate indicated heterophilic arthritis. Radiographic examination in 2 vultures demonstrated periarticular soft tissue swelling in both
birds and irregular articular surfaces with subchondral bone erosion in both elbows in 1 bird. Prolonged antibiotic therapy
administered in 2 birds did not improve the clinical signs.Necropsy and histological examination demonstrated a chronic
lymphoplasmacytic arthritis involving multiple joints and gastrocnemius tenosynovitis. Articular lesions varied in severity and ranged
from moderate synovitis and cartilage erosion and fibrillation to severe synovitis, diffuse cartilage ulceration, subchondral bone loss
and/or sclerosis, pannus, synovial cysts, and epiphyseal osteomyelitis. No walled bacteria were observed or isolated from the joints.
However, mycoplasmas polymerase chain reactions were positive in at least 1 affected joint from each bird. Mycoplasmas were
isolated from joints of 1 vulture that did not receive antibiotic therapy. Sequencing of 16S rRNA gene amplicons from joint samples
and the mycoplasma isolate identified Mycoplasma corogypsi in 2 vultures and was suggestive in the third vulture. Mycoplasma
corogypsi identification was confirmed by sequencing the 16S-23S intergenic spacer region of mycoplasma isolates. This report
provides further evidence that M. corogypsi is a likely cause of arthritis and tenosynovitis in American black vultures. Cases of
arthritis and tenosynovitis in New World vultures should be investigated for presence of Mycoplasma spp, especially M. corogypsi.
Pathological Features of Oxalate Nephrosis in a Population of Koalas
(Phascolarctos cinereus) in South Australia
The wild and captive koala population of the Mt Lofty Ranges in South Australia has a high level of renal dysfunction in which
crystals consistent with calcium oxalate have been observed in the kidneys. This study aimed to describe the pathological features
of the renal disease in this population, confirm the composition of renal crystals as calcium oxalate, and determine whether any
age or sex predispositions exist for this disease. A total of 51 koalas (28 wild rescues, 23 captive) were examined at necropsy, of
which 28 (55%) were found to have gross and/or histological evidence of oxalate nephrosis. Histopathological features included
intratubular and interstitial inflammation, tubule dilation, glomerular atrophy, tubule loss, and cortical fibrosis. Calcium oxalate
crystals were demonstrated using a combination of polarization microscopy, alizarin red S staining, infrared spectroscopy, and
energy-dispersive X-ray analysis with scanning electron microscopy. Uric acid and phosphate deposits were also shown to be
present but were associated with minimal histopathological changes. No significant differences were found between the numbers
of affected captive and wild rescued koalas; also, there were no sex or age predispositions identified, but it was found that oxalate
nephrosis may affect koalas <2 years of age. The findings of this study suggest that oxalate nephrosis is a leading disease in this
koala population. Possible causes of this disease are currently under investigation.
Systemic Distribution of Viral Antigen in Alpacas Persistently Infected With
Bovine Pestivirus
Recently, confirmed occurrences of persistent bovine viral diarrhea virus (BVDV) infection in North American alpacas have raised
concerns about the role of persistently infected (PI) alpacas in transmission of virus among herds, yet only limited pathological
descriptions of persistent infections in alpacas have been reported. The objective of this study was to characterize BVDV antigen
distribution in 10 PI alpacas of varying age and to compare viral antigen distribution and localization in tissues of PI alpacas with 5
PI calves of varying age. Ocular dysplasia was evident in 1 PI alpaca, constituting the first reported congenital ocular lesion in PI
alpacas. Viral antigen was widely distributed in alpaca tissues and was prominent in neurons, endothelial cells, and vascular tunica
media myocytes but had limited distribution in lymphoid tissues and moderate distribution in epithelium of several organ systems
of alpacas. Macrophages in the alpaca gastrointestinal system submucosa and lymph node medullary sinuses often had prominent
labeling. In addition, only 1 alpaca had antigen labeling in the bone marrow in contrast to PI cattle. Labeled cells in calf tissues were
more widely distributed, occurring prominently in lymphoid and epithelial tissues. Common features of the 2 host species were
widespread antigen labeling and absence of lymphoid depletion.
Interaction of Corynebacterium Pseudotuberculosis With Ovine Cells in Vitro
Caseous lymphadenitis is an infectious and contagious disease caused by Corynebacterium pseudotuberculosis, with a worldwide
distribution and high prevalence in small ruminant populations. This disease causes significant economic loss in small ruminants
through reduced meat, wool, and milk production. C. pseudotuberculosis can also affect horses, domestic and wild large ruminants,
swine, and man. It is considered an occupational zoonosis for humans. As part of in vitro investigations of the pathogenesis of
C. pseudotuberculosis, this study analyzed its capacity to adhere to and invade the FLK-BLV-044 cell line, derived from ovine
embryonic kidney cells. C. pseudotuberculosis showed a measurable capacity to adhere to and invade this cell line with no
significant differences between the four strains assessed. The incubation of the cell line at 4_C, pre-incubation with sugars,
complete and heat inactivated antiserum, and heat-killed and ultraviolet-killed bacteria produced a significant (P < 0.05) decrease in
the invasion efficiency or inability to invade the cell line. Plate counting and fluorescence studies showed intracellular bacteria
for up to 6 days. Non-phagocytic cells may therefore act as a suitable environment for C. pseudotuberculosis survival and play a
role in the spread of infection and/or maintenance of a carrier state.
Morphological and Immunohistochemical Characterization of Spontaneous
Thyroid Gland Neoplasms in Guinea Pigs (Cavia porcellus)
Reports of thyroid gland neoplasms in guinea pigs (Cavia porcellus) are rare, but thyroid tumors are among the most common
neoplasms seen in cases submitted to Northwest ZooPath. This report describes the histological and immunohistochemical
characteristics of thyroid neoplasms and lists the concurrent conditions found in guinea pig cases submitted to Northwest
ZooPath during 1998 to 2008. Of 526 guinea pig case submissions, 19 had thyroid neoplasms. The most common clinical findings
included a palpable mass on the ventral neck and progressive weight loss. Neoplasms were removed as an excisional biopsy from 7
guinea pigs, and 3 of these animals died within a few days after surgery. Radiographic mineral density was detected in 2 masses.
Five of the neoplasms were reported as cystic; 5 were black or a dark color. Histologically, the neoplasms were classified as
macrofollicular thyroid adenoma (8), thyroid cystadenoma (1), papillary thyroid adenoma (3), follicular thyroid carcinoma (5),
Vet Path January 2012
follicular-compact thyroid carcinoma (1), and small-cell thyroid carcinoma (1). Osseous metaplasia was present in 8 neoplasms,
and myeloid hyperplasia was present in 1 neoplasm. All 19 neoplasms were positive for thyroid transcription factor 1 and
thyroglobulin but negative for parathyroid hormone and calcitonin. Numerous concurrent diseases, including hepatopathies,
cardiomyopathies, and nephropathies, were present and considered to be the cause of death in many cases. Research is needed to
determine the appropriate modalities for antemortem diagnosis and treatment and whether thyroid disease plays a role in the
pathogenesis of chronic degenerative diseases in guinea pigs.
Probable Blastomyces dermatitidis Infection in a Young Rat
A 21-week-old male untreated control SHR/NCrlNarl rat was found dead during an experiment. Grossly, pulmonary lesions were
characterized by multifocal to coalescing firm gray-white nodules randomly scattered on the surface. Microscopically,
bronchopneumonia was found with pyogranulomas containing neutrophils, macrophages, and numerous thick-walled yeast cells.
Yeast cells, 5 to 25 mm in diameter, with no branching of hyphae were observed by staining with hematoxylin and eosin, Diff-Quik,
and periodic acid-Schiff. Furthermore, polymerase chain reaction (PCR) using panfungal and nested PCR primers were used for
detection of Blastomyces dermatitidis DNA in the lung tissue. After sequencing and matching with DNA sequences in the GenBank,
the sample showed a similarity of 94.6% and 97% to Ajellomyces dermatitidis (B. dermatitidis), respectively. On the basis of these
results, probable pulmonary blastomycosis was diagnosed. The origin of the infection in the colony rat is undetermined.
Pathologic Findings in Weedy (Phyllopteryx taeniolatus) and Leafy (Phycodurus
eques) Seadragons
A retrospective study of the pathologic findings in weedy (Phyllopteryx taeniolatus) and leafy (Phycodurus eques) seadragons was
performed on specimens submitted to 2 reference laboratories from 1994 to 2012 to determine the range and occurrence of
diseases affecting aquarium-held populations. One hundred two and 94 total diagnoses were recorded in weedy and leafy
seadragons, respectively. Two of the more common etiologic diagnoses in both species were mycobacteriosis and scuticociliatosis,
whereas myxozoanosis was common in weedy seadragons. Metazoan parasite infections were less common etiologic diagnoses.
There were no correlations between mycobacteriosis and ciliate protozoan infections in either species. Myxozoanosis was usually
found in combination with other diseases and, except for 1 case, was restricted to weedy seadragons. Phaeohyphomycosis,
nonmycobacterial bacterial infections, and trauma were also important but less frequent diagnoses. Intestinal coccidiosis was found
in weedy but not leafy seadragons. Mineralization of the swim bladder was detected in 26 of 197 leafy seadragons and only 2 of 257
weedy seadragons. Although weedy and leafy seadragons share certain diseases of significance to exhibit populations, there are
diseases unique to each species about which the veterinary pathologist, clinician, or diagnostician should be aware.
A Retrospective Study of Disease in Elasmobranchs
This report reviews diseases of 1546 elasmobranchs representing at least 60 species submitted to Northwest ZooPath from 1994
to 2010. Cownose rays (Rhinoptera bonasus) (78), southern rays (Dasyatis americana) (75), dusky smooth-hounds (Mustelus canis)
(74), bonnethead sharks (Sphyrna tiburo) (66), and bamboo sharks (Hemiscylliidae) (56) were the most commonly submitted
species. Infectious/inflammatory disease was most common (33.5%) followed by nutritional (11.9%, mostly emaciation), traumatic
(11.3%), cardiovascular (5.5%, mostly shock), and toxin-associated disease (3.7%). Bacterial infections (518/1546, 15%) included
sepsis (136/518, 26%), dermatitis (7%), branchitis (6%), and enteritis (4%). Fungal infections (10/1546, 0.6%) included dermatitis
(30%), hepatitis (30%), and branchitis (20%). Viral or suspected viral infections or disease processes (15/1546, 1%) included
papillomatosis (47%), herpesvirus (20%), and adenovirus (7%). Parasitic infections (137/1546, 9%) included nematodiasis (36/137,
26%), ciliate infections (23%), trematodiasis (20%), coccidiosis (6%), myxozoanosis (5%), amoebiasis (4%), cestodiasis (1%), and
flagellate infections (1%). Inflammation of unknown cause (401/1546, 26%) included enteritis (55/401, 14%), branchitis (9%),
encephalitis (9%), and dermatitis (7%). Traumatic diseases (174/1546, 11.3%) included skin trauma (103/174, 60%),
stress/maladaptation (9%), and gut trauma (7%). Toxicoses (57/1546, 4%) included toxic gill disease (16/57, 26%), gas bubble
disease (19%), fenbendazole (7%), ammonia (7%), chlorine (5%), and chloramine (3%). Species trends included visceral
nematodiasis in black-nosed sharks (Carcharhinus acronotus) (55%); sepsis in dusky smooth-hounds (41%), blue-spotted stingrays
(36%), southern rays (36%), and wobeggong sharks (Orectolobus spp) (69%); emaciation in bamboo (33%) and bonnethead (32%)
sharks and freshwater stingrays (Potamotrygon motoro) (32%); and trauma in bonnethead sharks (30%).
Pathology of Tumors in Fish Associated With Retroviruses : A Review
Thirteen proliferative diseases in fish have been associated in the literature with 1 or more retroviruses. Typically, these occur as
seasonal epizootics affecting farmed and wild fish, and most lesions resolve spontaneously. Spontaneous resolution and lifelong
resistance to reinfection are 2 features of some piscine retrovirus–induced tumors that have stimulated research interest in this
field. The purpose of this review is to present the reader with the epidemiological and morphological features of proliferative
diseases in fish that have been associated with retroviruses by 1 or more of the following methods: detection of C-type retroviruslike
particles or reverse transcriptase activity in tumor tissues; successful tumor transmission trials using well-characterized,
tumor-derived, cell-free inocula; or molecular characterization of the virus from spontaneous and experimentally induced tumors.
Two of the diseases included in this review, European smelt spawning papillomatosis and bicolor damselfish neurofibromatosis, at
one time were attributed to a retroviral etiology, but both are now believed to involve additional viral agents based on more
recent investigations. We include the latter 2 entities to update the reader about these developments.
Vet Path January 2012
A Review of Current State of Knowledge Concerning Perkinsus marinus Effects
on Crassostrea virginica (the eastern oyster)
The eastern oyster, Crassostrea virginica (Gmelin), is both an important component of our estuaries and an important farmed food
animal along the east and south coasts of the United States. Its populations have been significantly diminished in the wild due to
decades of overfishing beginning in the 1890s. Unfortunately, in 1950, a new disease in eastern oysters caused by the protistan
agent, Perkinsus marinus, was identified. The disease, resulting from infection with this protozoan, leads to high mortality of both
wild and cultured eastern oysters. Current restoration efforts are hampered by the disease, as is the aquaculture of this
economically important food. The parasite infects hemocytes and causes hemolytic anemia and general degeneration of the tissues,
leading to death. Ongoing research efforts are attempting to develop oysters resistant to the disease. Transport regulations exist
in may states. Infection with P. marinus is listed as a reportable disease by the World Health Organization.
Meningoencephalitis Associated With Carnobacterium maltaromaticumLike
Bacteria in Stranded Juvenile Salmon Sharks ( Lamna ditropis)
Juvenile salmon sharks beach yearly along the California coast, primarily during late summer and early fall. Fresh, frozen, and
formalin-fixed tissues from 19 stranded salmon sharks were collected for examination. Histopathology revealed meningitis or
meningoencephalitis in 18 of 19 shark brains with intralesional bacteria observed in 6 of the affected brains. Bacterial culture
of fresh or frozen brain, liver, and/or heart blood from 13 sharks yielded pure cultures characterized molecularly and/or
biochemically as belonging to the genus Carnobacterium. The 16s ribosomal DNA sequence of 7 tissue isolates from 7 separate
sharks was 99% homologous to C. maltaromaticum (GenBank FJ656722.1). Sequence of the large ribosomal DNA intergenic
spacer region (ISR) was 97% homologous to C. maltaromaticum (AF374295.1). This is the first report of Carnobacterium infection in
any shark species, and the authors posit that brain infection caused by Carnobacterium is a significant cause of morbidity and
mortality in juvenile salmon sharks found stranded along the Pacific coast of California.
Epizootic Neoplasia of the Lateral Line System of Lake Trout (Salvelinus
namaycush) in New York's Finger Lakes
This article documents an epizootic of inflammation and neoplasia selectively affecting the lateral line system of lake trout
(Salvelinus namaycush) in 4 Finger Lakes in New York from 1985 to 1994. We studied more than 100 cases of this disease.
Tumors occurred in 8% (5/64) of mature and 21% (3/14) of immature lake trout in the most severely affected lake. Lesions
consisted of 1 or more neoplasm(s) in association with lymphocytic inflammation, multifocal erosions, and ulcerations of the
epidermis along the lateral line. Lesions progressed from inflammatory to neoplastic, with 2-year-old lake trout showing locally
extensive, intense lymphocytic infiltrates; 2- to 3-year-old fish having multiple, variably sized white masses up to 3 mm in diameter;
and fish over 5 years old exhibiting 1 or more white, cerebriform masses greater than 1 cm in diameter. Histologic
diagnoses of the tumors were predominantly spindle cell sarcomas or benign or malignant peripheral nerve sheath neoplasms,
with fewer epitheliomas and carcinomas. Prevalence estimates did not vary significantly between sexes or season. The cause of
this epizootic remains unclear. Tumor transmission trials, virus isolation procedures, and ultrastructural study of lesions failed
to reveal evidence of a viral etiology. The Finger Lakes in which the disease occurred did not receive substantially more chemical
pollution than unaffected lakes in the same chain during the epizootic, making an environmental carcinogen an unlikely primary
cause of the epizootic. A hereditary component, however, may have contributed to this syndrome since only fish of the
Seneca Lake strain were affected.
Ulcerative Umbrellar Lesions in Captive Moon Jelly (Aurelia aurita) Medusae
Over a period of 6 months, dozens of moon jelly (Aurelia aurita) medusae from a single-species exhibit at the California Science
Center (CSC) developed exumbrellar ulcers. Ulcers were progressive, causing umbrellar creases that expanded radially to the
bell rim and occasional adoral erosions that extended into gastrovascular cavities. Husbandry interventions, including addition
of ultraviolet light sterilizers, repopulation with fresh cultures, and enclosure disinfection, did not arrest the recurrence of lesions.
Biopsies or whole specimens representing 17 medusae (15 affected and 2 grossly unaffected) from CSC and 2 control medusae
from Aquarium of the Pacific were submitted to a private diagnostic laboratory and processed for light and electron microscopy.
Microscopic lesions were present in all CSC medusae and were not observed or negligible in control medusae. Lesions included
ulceration, necrosis, and hyperplasia in all umbrellar layers, with most severe lesions in the exumbrella and amoebocyte infiltration
in the underlying mesoglea. Special stains, electron microscopy, and fungal culture did not associate microorganisms with the
lesions. Bacterial cultures from the CSC population consistently grew Shewanella and Vibrio spp, both of which were considered
commensal. Trauma and environmental stress are proposed as possible causes for the ulcers.
Tumoral Calcinosis Form of Hydroxyapatite Deposition Disease in Related RedBellied Short-Necked Turtles, Emydura subglobosa
Ten of 12 red-bellied short-necked turtles from a single clutch presented at 9 months of age with multiple white to tan nodules on
their feet. Histologically, the nodules were composed of large periarticular deposits of mineralized crystalline material that
extended into the joint spaces of interphalangeal joints and was surrounded by granulomatous inflammation and fibrosis.
Crystallographic analysis determined the material to be apatite (calcium phosphate hydroxide) consistent with the tumoral calcinosis
form of hydroxyapatite deposition disease (HADD). HADD has previously been described in aquatic turtles and rarely lizards
and must be differentiated from gout in reptiles. A cause for the tumoral calcinosis lesions in these turtles could not be
determined; however, based on previous reports in this species, a species-specific predilection, in conjunction with unknown
environmental factors, is suspected. The use of the terms HADD, pseudogout (calcium pyrophosphate crystal deposition disease),
and calcinosis circumscripta has been inconsistent, creating confusion in the literature.
Vet Path January 2012
Subcuticular Urate Accumulation in an American Lobster (Homarus americanus)
An unusually ‘‘lumpy’’ lobster, Homarus americanus, was presented to the Atlantic Veterinary College Lobster Science Centre for
evaluation. The lobster was weak with numerous pale, raised, and flat areas (diameter, 3–15 mm) on the exoskeleton, some of
which were ulcerated. On postmortem examination, the pale areas corresponded to accumulations of viscous to free-flowing
white material, which was found in only the subcuticular connective tissues. No internal organs were affected. Direct light
examination of nonstained impression smears of the material showed abundant crystals resembling uric acid, amorphous urates,
and sodium urate, which were readily soluble in 1 M potassium hydroxide. Wright-Giemsa stained imprints showed numerous fine,
rounded, nonstaining granules free in the background and within individual round cells. Fourier-transformed infrared spectroscopy
confirmed the presence of urates or mixed urate salts. Hemolymph plasma urea (1.7 mmol/liter) and uric acid (287
mmol/liter) concentrations were slightly higher than those seen with 36-hour emersion. Histologic sections showed aggregates
of vacuolated mononuclear cells in the loose subcuticular connective tissue occasionally infiltrating between underlying muscle
fibers. Grossly visible urate deposits are occasionally documented in land crabs and rarely reported in the blue crab; none, however,
are associated with deformation of the cuticle. Possible etiologies include increased uric acid intake or production or
decreased excretion. Anecdotal reports of similarly affected lobsters have been received but are intermittent and undocumented.
Zebrafish (Danio rerio) as a Screen for Attenuation of Lancefield Group C
Streptococci and a Model for Streptococcal Pathogenesis
Group C streptococci are highly contagious pyogenic bacteria responsible for respiratory tract, lymph node, urogenital tract, and
wound infections. Wild-type strains of Streptococcus equi ssp equi (S. equi) and Streptococcus equi ssp zooepidemicus (S. zoo) as
well as a commercially available modified live vaccine strain of S. equi were evaluated for virulence in zebrafish. Survival times,
histologic lesions, and relative gene expression were compared among groups. Based on the intramuscular route of infection,
significantly shorter survival times were observed in fish infected with wild-type strain when compared to modified live vaccine and
S. zoo strains. Histologically, S. zoo–infected fish demonstrated a marked increase in inflammatory infiltrates (predominantly
macrophages) at the site of infection, as well as increased cellularity in the spleen and renal interstitium. In contrast, minimal cellular
immune response was observed in S. equi–injected fish with local tissue necrosis and edema predominating. Based on whole
comparative genomic hybridization, increased transcription of positive acute-phase proteins, coagulation factors, and antimicrobial
peptides were observed in S. equi–injected fish relative to S. zoo–injected fish, while mediators of cellular inflammation, including
CXC chemokines and granulin, were upregulated in S. zoo–injected fish relative to S. equi–injected fish. In a screen of 11 clinical
isolates, S. equi strains with a single nucleotide deletion in the upstream region of szp, a known virulence factor of streptococci,
were found to be significantly attenuated in zebrafish. These collective findings underscore the value of the zebrafish as a model of
streptococcal pathogenesis.
Zebrafish Models for Human Cancer
For decades, the advancement of cancer research has relied on in vivo models for examining key processes in cancer
pathogenesis, including neoplastic transformation, progression, and response to therapy. These studies, which have traditionally
relied on rodent models, have engendered a vast body of scientific literature. Recently, experimental cancer researchers have
embraced many new and alternative model systems, including the zebrafish (Danio rerio). The general benefits of the
zebrafish model for laboratory investigation, such as cost, size, fecundity, and generation time, were quickly superseded by
the discovery that zebrafish are amenable to a wide range of investigative techniques, many of which are difficult or
impossible to perform in mammalian models. These advantages, coupled with the finding that many aspects of
carcinogenesis are conserved in zebrafish as compared with humans, have firmly established a unique niche for the zebrafish
model in comparative cancer research. This article introduces methods for generating cancer models in zebrafish and
reviews a range of models that have been developed for specific cancer types.
Pharyngeal Odontoma in an Adult Walleye (Sander vitreus)
An adult walleye (Sander vitreus) was submitted to Cornell University for evaluation of a hard pale-tan pharyngeal mass attached to
the gill arches. Dozens of hard white conical structures radiated from the surface. Microscopically, conical structures were identified
as denticles and rested on plates of dysplastic orthodentine, cementum, and acellular bone. A diagnosis of compound
odontoma was made based upon the presence of proliferative epithelial and mesenchymal odontogenic tissues that recapitulated
tooth structures normally present on gill rakers. Odontomas are classified as hamartomas and typically develop in immature
diphyodont mammals. The pharyngeal location and lifelong regeneration of teeth in fish, however, both qualify the present
diagnosis in the pharyngeal region of an adult teleost. Ontogenic and morphologic differences between mammalian and piscine
dentition and differentials for tooth-bearing tumors in fish are presented within the context of a developmental anomaly.
Wildlife Reservoirs of Bovine Tuberculosis Worldwide: Hosts, Pathology,
Surveillance, and Control
Bovine tuberculosis due to Mycobacterium bovis is a zoonotic disease classically carried by cattle and spilling over into humans
primarily by the ingestion of milk. However, in recent decades, there have been many endemic geographic localities whereM. bovis
has been detected infecting wildlife reservoirs, limiting the progress toward eradication of this disease from cattle. These include
cervids in North America, badgers in Great Britain, feral pigs in Europe, brushtailed possums in New Zealand, and buffalo in South
Africa. An overview of these wildlife hosts will provide insight into how these reservoirs maintain and spread the disease. In
addition, the authors summarize the pathology, current ongoing methods for surveillance, and control. In many instances, it has
proven to be more difficult to control or eradicate bovine tuberculosis in wild free-ranging species than in domesticated cattle.
Furthermore, human influences have often contributed to the introduction and/or maintenance of the disease in wildlife species.
Finally, some emerging themes regarding bovine tuberculosis establishment in wildlife hosts, as well as conclusions regarding
management practices to assist in bovine tuberculosis control and eradication in wildlife, are offered.
Vet Path January 2012
Macroscopic, Histologic, and Ultrastructural Lesions Associated With Avian
Keratin Disorder in Black-Capped Chickadees ( Poecile atricapillus)
An epizootic of beak abnormalities (avian keratin disorder) was recently detected among wild birds in Alaska. Here we describe
the gross, histologic, and ultrastructural features of the disease in 30 affected adult black-capped chickadees (Poecile atricapillus).
Grossly, there was elongation of the rhamphotheca, with varying degrees of lateral deviation, crossing, and gapping between the
upper and lower beak. Not uncommonly, the claws were overgrown, and there was alopecia, scaling, and crusting of the skin. The
most prominent histopathologic features in the beak included epidermal hyperplasia, hyperkeratosis, and core-like intrusions of
necrotic debris. In affected birds, particularly those with moderate to severe beak overgrowth, there was remodeling of premaxillary
and mandibular bones and various dermal lesions. Lesions analogous to those found in beaks were present in affected claws,
indicating that this disorder may target both of these similar tissues. Mild to moderate hyperkeratosis occurred in other keratinized
tissues, including skin, feather follicles, and, occasionally, sinus epithelium, but typically only in the presence of microbes. We
did not find consistent evidence of a bacterial, fungal, or viral etiology for the beak lesions. The changes observed in affected birds
did not correspond with any known avian diseases, suggesting a potentially novel hyperkeratotic disorder in wild birds.
Pathology of Experimental Aerosol Zaire Ebolavirus Infection in Rhesus
Macaques
There is limited knowledge of the pathogenesis of human ebolavirus infections and no reported human cases acquired by the
aerosol route. There is a threat of ebolavirus as an aerosolized biological weapon, and this study evaluated the pathogenesis of
aerosol infection in 18 rhesus macaques. Important and unique findings include early infection of the respiratory lymphoid tissues,
early fibrin deposition in the splenic white pulp, and perivasculitis and vasculitis in superficial dermal blood vessels of haired skin
with rash. Initial infection occurred in the respiratory lymphoid tissues, fibroblastic reticular cells, dendritic cells, alveolar
macrophages, and blood monocytes. Virus spread to regional lymph nodes, where significant viral replication occurred. Virus
secondarily infected many additional blood monocytes and spread from the respiratory tissues to multiple organs, including the
liver and spleen. Viremia, increased temperature, lymphocytopenia, neutrophilia, thrombocytopenia, and increased alanine
aminotransferase, aspartate aminotransferase, g-glutamyl transpeptidase, total bilirubin, serum urea nitrogen, creatinine, and
hypoalbuminemia were measurable mid to late infection. Infection progressed rapidly with whole-body destruction of lymphoid
tissues, hepatic necrosis, vasculitis, hemorrhage, and extravascular fibrin accumulation. Hypothermia and thrombocytopenia were
noted in late stages with the development of disseminated intravascular coagulation and shock. This study provides unprecedented
insight into pathogenesis of human aerosol Zaire ebolavirus infection and suggests development of a medical countermeasure
to aerosol infection will be a great challenge due to massive early infection of respiratory lymphoid tissues. Rhesus macaques
may be used as a model of aerosol infection that will allow the development of lifesaving medical countermeasures under the Food
and Drug Administration’s animal rule.
Fatal Wedelia glauca Intoxication in Calves Following Natural Exposure
A group of 342 beef calves, corralled in the Patagonia region of Argentina, were fed alfalfa hay that had been inadvertently
contaminated with Wedelia glauca. A total of 147 (43%) calves died within 4 days. Pathologic findings in 2 calves were diffuse
centrilobular hepatic necrosis and hemorrhage with edema in the gallbladder, common bile duct, and choledochoduodenal
junction. Epidermal fragments of W. glauca were identified in rumen contents by microscopy. Intact W. glauca plants and leaf
fragments were found in the hay. Patches of defoliated W. glauca were also identified in the alfalfa pasture from which the hay had
been baled.
Histologic and Immunohistochemical Classification of 41 Bovine Adrenal Gland
Neoplasms
Tumors of the adrenal glands are among the most frequent tumors in cattle; however, few studies have been conducted to
describe their characteristics. The aim of this study was to classify 41 bovine adrenal neoplasms from 40 animals based on
macroscopic and histologic examination, including electron microscopy and immunohistochemistry for melan A, synaptophysin,
chromogranin A, vimentin, pan-cytokeratin, 20,30-cyclic nucleotide-30-phosphohydrolase (CNPase), and Ki-67. The tumors were
classified as 23 adrenocortical adenomas, 12 adrenocortical carcinomas, 2 schwannomas, 2 pheochromocytomas (1 malignant),
and 1 ganglioneuroma. Five histologic features were characteristic of metastasizing adrenocortical tumors: invasion of the capsule,
vascular invasion, diffuse growth pattern, spindle-cell morphology, and nuclear pleomorphism. Adrenocortical tumors with at
least 3 of these features were classified as malignant. Immunohistochemically, adrenocortical tumors expressed melan A (16/
19), vimentin (14/26), cytokeratin (11/26), and chromogranin A (9/27), whereas pheochromocytomas expressed chromogranin
A (2/2), synaptophysin (2/2), and vimentin (1/2). Both schwannomas expressed CNPase. An immunohistochemistry panel consisting
of antibodies against melan A, synaptophysin, and CNPase was considered most useful to classify bovine adrenal tumors.
However, the distinction between benign and malignant adrenocortical tumors was based on histologic features as in human
medicine.
TP53 Intronic Mutations in Bovine Enzootic HematuriaAssociated Urinary
Bladder Tumors
Tumor protein 53 (TP53) is a tumor suppressor gene that is frequently mutated in urinary bladder tumors in both humans and
animals. In cattle, urinary bladder tumors have been reported as occurring spontaneously as well as in conjunction with bracken
fern consumption-induced bovine enzootic hematuria (BEH). The goal of this study was to evaluate various types of bovine urinary
bladder neoplasms for the presence of TP53 alterations, using the polymerase chain reaction–single-strand conformation
polymorphism (PCR-SSCP) method. DNA was extracted from both epithelial and mesenchymal urinary bladder tumor samples
Vet Path January 2012
in cattle, associated with the chronic consumption of bracken fern. PCR was performed using primers targeted to exons 5 to 8,
following electrophoresis and isolation, and the products were assessed by SSCP. Tumors in which alterations in the
electrophoresis patterns were noted included hemangiomas, papillomas, and carcinomas in situ. Exemplars of these tumor types
were selected for sequencing, and although no changes were noted in the 5 to 8 exon range, on either side of the designed primers
for exon 6, there was some portion of intron 6 in which sequencing demonstrated a deletion of the thyamine nucleotide at
position 9332. In summary, although mutations were not observed within exons 5 to 8, this represents the first report of an
intronic mutation in the TP53 gene in association with bovine urinary bladder tumors. Mutations within introns can predispose
tissues to the development of cancer, and therefore, a possible association between mutations of the introns of TP53 and the
development of urinary bladder tumors in cattle with BEH should be further investigated.
Replication of 2 Subtypes of Low-Pathogenicity Avian Influenza Virus of Duck
and Gull Origins in Experimentally Infected Mallard Ducks
Many subtypes of low-pathogenicity avian influenza (LPAI) virus circulate in wild bird reservoirs, but their prevalence may vary
among species. We aimed to compare by real-time reverse-transcriptase polymerase chain reaction, virus isolation, histology,
and immunohistochemistry the distribution and pathogenicity of 2 such subtypes of markedly different origins in Mallard ducks
(Anas platyrhynchos): H2N3 isolated from a Mallard duck and H13N6 isolated from a Ring-billed Gull (Larus delawarensis).
Following intratracheal and intraesophageal inoculation, neither virus caused detectable clinical signs, although H2N3 virus infection
was associated with a significantly decreased body weight gain during the period of virus shedding. Both viruses replicated in the
lungs and air sacs until approximately day 3 after inoculation and were associated with a locally extensive interstitial, exudative, and
proliferative pneumonia. Subtype H2N3, but not subtype H13N6, went on to infect the epithelia of the intestinal mucosa and
cloacal bursa, where it replicated without causing lesions until approximately day 5 after inoculation. Larger quantities of subtype
H2N3 virus were detected in cloacal swabs than in pharyngeal swabs. The possible clinical significance of LPAI virus-associated
pulmonary lesions and intestinal tract infection in ducks deserves further evaluation.
Naturally Occurring Parelaphostrongylus tenuisAssociated Choriomeningitis in
a Guinea Pig With Neurologic Signs
An adult male guinea pig (Cavia porcellus) with a 1-month history of hind limb paresis, torticollis, and seizures was euthanized and
submitted for necropsy. Gross examination was unremarkable, but histologic examination revealed multifocal eosinophilic and
lymphoplasmacytic choriomeningitis and cross sections of nematode parasites within the leptomeninges of the midbrain and
diencephalon. Morphologic features of the nematode were consistent with a metastrongyle, and the parasite was identified as
Parelaphostrongylus tenuis by polymerase chain reaction testing and nucleotide sequencing. Further questioning of the owner
revealed that the guinea pig was fed grass from a yard often grazed by white-tailed deer (Odocoileus virginianus). To the authors’
knowledge, this is the first report of a naturally occurring P. tenuis infection in a guinea pig.
Meeting Report : Urinary Pathology; Sixth Research Triangle Park Rodent
Pathology Course
Urinary system toxicity is a significant concern to pathologists in the hazard identification, drug and chemical safety evaluation, and
diagnostic service industries worldwide. There are myriad known human and animal urinary system toxicants, and investigatory
renal toxicology and pathology is continually evolving. The system-specific Research Triangle Park (RTP) Rodent Pathology
Course biennially serves to update scientists on the latest research, laboratory techniques, and debates. The Sixth RTP Rodent
Pathology Course, Urinary Pathology, featured experts from the government, pharmaceutical, academic, and diagnostic arenas
sharing the state of the science in urinary pathology. Speakers presented on a wide range of topics including background lesions,
treatment-related non-neoplastic and neoplastic lesions, transgenic rodent models of human disease, diagnostic imaging,
biomarkers, and molecular analyses. These seminars were accompanied by case presentation sessions focused on usual and
unusual lesions, grading schemes, and tumors.
Diagnostic Exercise : Multiple Skin Nodules in a Cat
A 10-year-old, neutered, male, domestic short-haired cat had numerous, small, firm, round, red, nonpruritic, nonpainful,
dermal nodules 5–16 mm in diameter that ruptured within 48 hours of their appearance and subsequently crusted over.
The masses were located in all regions of the body. One mass was excised from the dorsal right carpus and examined
histologically, and 2 masses from the interscapular region were cultured for bacteria. The excised dermal mass from the
carpus effaced normal dermal architecture, pressed tightly against the epidermis, and was composed of tightly packed round
to polyhedral cells that extended to the deep margins of the sections. The overlying epidermis was extensively ulcerated
and vesiculated with intraepidermal nests of cells identical to those in the dermis. There was marked anisokaryosis in the
deeper regions of the mass with numerous multinucleated cells and cells with giant bizarre nuclei. The histological appearance
and CD18 immunocytochemical staining of this mass are consistent with a diagnosis of feline progressive epitheliotropic
dendritic cell histiocytosis.