ISRAEL JOURNAL OF
VETERINARY MEDICINE
TRANSMISSIBLE VENEREAL TUMORS DETECTED
IN THE EXTRAGENITAL ORGANS OF DOGS
Vol. 57 (2) 2002
A. Gurel1, B. Kuscu1, E. G. Gulanber2 and S. S. Arun1
1. Department of Pathology, and, 2. Department of Surgery,
University of Istanbul, Faculty of Veterinary Medicine, Avcilar-Istanbul,
Turkey.
Abstract
Transmissible venereal tumors detected in the extragenital regions of eight dogs of various
ages, breeds and sex were evaluated clinically and pathologically. Seven of these tumors
were found to be of primary origin.Only in one case, was TVT diagnosed also in the vagina
of the animal.
Biopsies collected from the extragenital tumor foci of 6 male and 2 female dogs were fixed
in formalin and histology sections were prepared from these specimens and examined under
light microscope.
Three of these tumors were located in the nasal mucosa, 3 on the dorsal side of the thorax,
1 in gingiva and one in gluteal region. These tumors were approximately 0,5 X 2 cm. in size
and appeared as a unique mass or two solitary masses. They were soft in consistency. All
tumor cases involving the nasal mucosa were accompanied by a bloody nasal discharge.
The microscopical appearance of all tumors detected in various regions was histologically
similar to the appearance of TVT in the genital regions.
In this study, 8 extragenital localisation of these tumors out of a total of 90 TVT cases
suggest that although they are not as frequent, it is possible to encounter them in other parts
of the body.
Introduction
Transmissible venereal tumor (TVT) is the only encountered tumor in dogs that can be
transmitted by mating and also experimentally. Sticker was the first to perform detailed
studies on this tumor, in the first decade of the 20th century. Since then, the tumors are
known as Sticker’s sarcoma. They are also known as transmissible venereal tumor, venereal
granuloma, canine condyloma or infectious sarcoma (1-3).
The tumor is recognized in all dog breeds in various parts of the world, especially in tropical
and subtropical zones. However, it is particularly common in stray dogs, which mate without
any control after reaching sexual maturation. TVT can be experimentally transmitted to
wolves, jackals, coyotes and red foxes (1,3). In reports from Turkey concerning canine
tumors, these tumors are most frequently encountered (4-11).
Sticker’s tumors are most common in sexually mature dogs aged 2 to 5 years (1-3). The
tumor is transmitted by direct contact of the mucous membranes, damage to the mucous
membrane may enhance transmission (1,3). Because the genital mucosae of both sexes are
most vulnerable to injury at the time of mating, this predisposes them to tumor formation (16,11). Although it is rare, these tumors can be encountered in extra-genital regions (1-3,1218).
TVT is composed histologically by round, ovoid or polyhedral cells. These cells have large,
round hyperchromatic nuclei and centrally situated unique nucleoli. Also, they have
moderately abundant eosinophilic cytoplasm. A notable number of mitotic figures can be
observed in parenchymal cells that make up these tumors. The tumor is rich in cells, the
stroma which contains the blood vessels is relatively narrow and can be observed as thin
lines within the clusters of tumor cells (1-5,19,20).
In this study, we have performed a clinical and pathological evaluation of extra-genital TVT
cases from various biopsy materials sampled from 8 dogs of variable age, breed and sex,
presented to our department.
Materials and Methods
Various biopsy specimens taken from extra-genital tumoral masses of 8 dogs that were
sent to our laboratory from various clinics between the years 1997 to 2000.
The biopsy specimens were routinely fixed in 10 % neutral buffered formaline solution and
then embedded in paraffin wax, sections of 5-7 µm, stained with haematoxyline and eosin
(21), and examined under a light microscope.
Results
Table 1 describes the signalment, location of the tumor, its characteristics, and clinical
findings of 8 cases with extra-genital TVT.
Table 1: Specifications and some clinical characteristics of the biopsy used in the study.
No
Breed
Age
(Y)
Sex
Location of
the Lesion
Size
Characteristics
Clinical
Findings
1
Dalmatian*
3
M
Nasal
1x1 cm
Brownish,
Bloody nasal
soft
discharge,
consistency
deformation of
mucosa
nasal bone
2
Collie
2
M
Nasal
0.5x1 cm
Soft
Bloody nasal
mucosa
2 pieces.
consistency
discharge for
1,5-2 month.
Deformation of
nasal bone
3
Crossbred
8
F
Slightly hard
Developed in
Gluteal
1 cm in
consistency,
approx. 3
region
diameter
round
months
shaped
2 pieces
4
5
Terrier
Boxer
10
6
M
M
Maxillar
approx.
Slightly hard,
Grew 2-fold in
gingiva
0.5x0.5
xm
oval mass
1 month
1 pieces;
Mucosa is
Nasal
approx.
filled with
Bloody nasal
Mucosa
0,5 cm in
this mass
discharge
diameter
Pendular,
2 pieces, TVT
6
Crossbred
3,5
F
Dorsal skin
1,5x2 cm
Pate-like
also
of thorax
in
consistency,
diagnosed in
diameter
pendular
vagina. Poor
general
condition
7
German
5
M
Shepherd
Thorax; sub-
1 piece;
White, Soft
cutaneous
4x4,5 cm
consistency
Dorsal of
8
Boxer
6
F
thorax, sub
cutaneous
-
Developed in 2
1x2 cm
White, soft,
2 pieces
months. Poor
general
condition
* Also refer to figure1
Histopathological examination of the specimen excised from the gingiva revealed large
areas of erosion. Inflammatory cell infiltrations, mainly neutrophils were noted in some parts
of the mucosa. Moreover, it was noticed that the basal cells of the stratified squamous
epithelium had formed papillary projections towards the muscular layer. Atypical tumoral cells,
round or polygonal in shape, with large nuclei that contain unique nucleoli and a slight pinkish
cytoplasm infiltrated throughout the sub mucosal muscular layer. This infiltrate had destroyed
and replaced the muscle fibers. The majority of the cells were hyperchromatic, and numerous
mitotic figures were seen. A fine stromal fibrovascular network proliferated between these
cells (Fig. 2).
In biopsies excised from the nasal regions, the mucosae and deeper layers were seen to be
infiltrated by tumor cells with similar characteristics to those described above. In some areas,
focal necrosis with haemorrhage was also present (Fig. 3).
In the tumors that were taken from the skin, a thick muscular “knob” was detected, while
small groups of muscle cells could be observed particularly within the tumor cell foci located
at the periphery. The tumor parenchyma was composed of numerous cells having similar
structures as those described. Various stages of mitosis were prominent in these cells. The
stromal tissue of thin fibrous filaments that was located between the parenchymal cells were
determined to be more extensive compared to the others. The parenchyma was composed of
various cell groups that contained different number of cells.
Fig. 1: MRI (Magnetic Resonance Imaging) of dorsoventral-saggital plane of cranium. TVT
localized in the left nasal lumen.
Fig. 2: Tumor cell infiltration in the mucosa of the gingiva. H&E X 100.
Fig. 3: Tumor cell infiltration in the nasal mucosa. Hyperchromatic cells with vesicular nuclei and
abundant mitotic figures. H&E X 250.
Discussion
Transmissible veneral tumor is a frequently encountered tumor type in Turkey (4-10) and
other countries (1-3,14,19,20). This tumor mostly develops in the genital organs of both sexes
and is generally considered as a benign tumor (1-6,11). However, metastases may also occur
in some of the cases and lesions may sometimes be observed in extra-genital region of some
animals.The incidence of metastasis is quite low and occurs in 5 % or less of the cases. It is
reported that metastases may occur in regional lymph nodes and internal organs such as the
spleen, liver, kidney and brain (1-3,16,17,22,25). It is also reported that metastases may
rarely occur in ocular, nasal or gingival regions due to activities such as smelling, licking and
scratching (1-3,12-18). In this study, eight TVT cases were detected, of which 3 were in nasal,
3 in thoracic, 1 in the gingival and 1 the in gluteal region. According to anamnesis, clinical and
microscopical examinations, all tumors except the one detected on the dorsal side of the
thorax were concluded to be primary tumors. In this period, a total of 90 TVT diagnoses were
recorded among the dogs or canine biopsies that were received by the clinics and laboratory
of our faculty (4,12).
The extra-genital location of tumors in the eight patients suggests that although it is quite
infrequent, these tumors may be encountered at different sites. The destruction or the
erosions of the mucosa has an important impact on tumor formation in extra-genital regions
(1-3). The identification of individuals by smelling the genital areas is a common type of
behaviour of canine species. The location of transmissible veneral tumors on the nasal
mucosa is explained by inspiration during the action of smelling. Also, the proliferation of TVT
on gingivae are explained by implantation of tumor cells on erosions already present on the
gingivae. Transmission of tumors to the eyes and various regions of the skin are facilitated
during the action of scratching (1-3,13-15,18,23,25).
Due to the excessive number of stray dogs, the incidence of TVT in Turkey is high (4-10).
The incidence of genital and extra-genital TVT has not yet been determined. In our search of
the literature, 5 case reports, each describing 1 case were located (12,16,17,22,24). We
suggest that our diagnosis of 8 extra-genital TVT cases out of a total of 90 patients with TVT
which were received over a period of 3 years of observation may give an estimate about the
incidence of extra-genital TVT cases. In a report from Nairobi, Kenya TVT was diagnosed in
181 patients out of a total of 1535 tumor cases at a small animal clinic. Of these cases, only 8
were reported as having extra-genital involvement (15). In addition, metastatic TVT was
reported in the eye of a 5 year old Pointer which had TVT on its penis (16).
Perez et. al. (13) have reported 3 primary TVT cases in the maxillary and nasal sinuses,
which is quite similar to our findings. As explained in this report, a bloody nasal discharge at
the onset and deformation of the nasal bone in the preceeding period was noted
(3,13,14,18,25). According to these observations, we assume that TVT should also be
considered in the etiology of a particular pathology associated with permanent nasal
discharge.
Although 6 of the 8 TVT cases were diagnosed in males and 2 in females, there is no
evidence of a particular predilection associated with sex and breed in detailed studies.
Moreover, ages between 2 and 5 years are indicated to be the most common time for the
incidence of these tumors (1-3). Also in our study, it was seen that all dogs involved in our
report were sexually mature and all were within these age limits.
TVT which proliferate in genital organs have a variable size and width, a cauliflower-like
appearance and are generally in the form of a mass bearing a stalk or in the form of small
nodules. Generally, their outer surface is ulcerated. As it may be seen in our study and in
relevant studies (1,3,12,14,25), extra-genital TVT are generally observed in nodular form,
bearing ulcerations of variable sizes which may invade the mucosa and submucosa. We
suggest that these pathological findings may help clinicians in diagnosing these tumors.
In this report, it was seen that the cells involved in extra-genital TVT were similar to the
ones detected in genital regions (1-7,11,19,20). Thus, we suggest that these extra-genital
tumors can easily be diagnosed by microscopical examination. However, cutaneous
lymphoma, cutaneous histiocytoma and mast cell tumors should also be considered in
differential diagnosis.
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