Practical Oncology
Round Cell Tumors
Wendy Blount, DVM
Round Cell Tumors
• Lymphoma
• Mast Cell Tumor
• Plasma Cell Tumor
• Extramedullary Plasmacytoma
• Multiple myeloma
• Histiocytic Disease
• Transmissible Venereal Tumor
Diagnosis
• Generally diagnosed with
cytology, as they exfoliate well
• May need histopathology if
anaplastic
• Immunohistochemistry if
markedly anaplastic
• Gives information about
prognosis
Plasmacytoma
• Round, button like tumors on the skin
and mucous membranes
• Technically malignant
• Usually behave benignly if
extramedullary
• Surgery is curative if borders clean
• Radiation curative if not resectable
Plasmacytoma
Plasmacytoma
Multiple Myeloma
• Malignant plasma cells proliferate in bone
marrow and are released into circulation
• Malignant cells found in
• Skeleton
• Lymph nodes and spleen
• Kidney and liver
• Produce large amounts of a specific Ig or
part of an Ig
• Mono or biclonal gammopathy
• Bence Jones protein is the light chain
• heavy chain or paraprotein also possible
Multiple Myeloma
Clinical Signs
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Lethargy, anorexia weight loss
Lameness + pathologic fracture
PU-PD
Hyperesthesia
Hyperviscosity Syndrome
Immunosuppression – cytopenias & inhibition of
humoral immunity
• anemia more common than leukopenia or
thrombocytopenia
• Hypercalcemia
• Azotemia - hypercalcemia, renal infiltration,
hyperviscosity
Multiple Myeloma
Hyperviscosity syndrome (TP >10)
• Heart failure
• Reduced flow through small vessels
• plasma volume expansion
• volume overload
• Myocardial hypoxia
• Neurologic signs due to hypoxia
• Seizures, disorientation, ataxia
• Peripheral neuropathy
Multiple Myeloma
Hyperviscosity syndrome (TP >10)
• Bleeding diathesis
• Capillary damage from hypoxemia
• Inflammatory coagulopathy
• Epistaxis, gingival bleeding
• Retinal detachment, hyphema,
secondary glaucoma, blindness
• Renal ischemia
Multiple Myeloma
Diagnosis – 2 of 5
1. Paraproteinemia (monoclonal gammopathy)
• Serum protein electrophoresis
• Also caused by rickettsial disease
2. Osteolytic bone lesions (punched out)
• Generalized osteopenia
• Pathologic fractures
• More common in dogs than cats
• Radiograph spine, ribs and limbs
• Biopsy lytic lesion and take bone
marrow sample
Multiple Myeloma
Diagnosis – 2 of 5
3. >20% plasma cells in the bone marrow
• DDx – atopy, rickettsial infection, FIP,
Leishmania spp, heartworm disease
4. Bence Jones proteinuria
• Not detected on urine dipstick
5. Infiltration of liver, spleen and skin with
plasma cells (cats)
Multiple Myeloma
Treatment
• Treat hyperviscosity
• diuresis
• Whole blood or platelet rich plasma for
bleeding diathesis
• Treat hypercalcemia (pamidronate)
• Plate pathologic fractures
• Treat secondary infection
• Treat renal failure
• Chemotherapy melphalan and prednisone,
with or without 1 dose cyclophosphamide
Multiple Myeloma
Rescue Therapy – 3 week cycle
• Week 1 – doxorubicin 30 mg/m2 IV
• Start prednisone 1 mg/kg PO SID
• Week 2, 3 – vincristine 0.7 mg/m2
• Wean off prednisone of possible
Multiple Myeloma
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Multiple Myeloma
Prognosis
• Short term prognosis is good
• median survival 540 days (2.5 years) with
treatment
• Long term prognosis poor, as recurrence
is expected
• Bone pain and pathologic fractures main
cause of morbidity and mortality
• Negative prognostic indicators:
• Hypercalcemia
• Bence Jones proteinuria
• Extensive bony lysis
Histiocytic Disease
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Histiocytoma
Cutaneous histiocytosis
Systemic histiocytosis
Localized histiocytic sarcoma
Malignant histiocytosis
• aka disseminated histiocytic
sarcoma
Histiocytoma
• Single alopecic button like mass
• Usually young dogs
• Usually spontaneously regresses
• Can take 2-3 months
• Aspiration can induce regression
• If large, may need to be resected
• If >2 yrs old, remove for histopath
• Rare in cats
• Cytology – small lymphocytes may
be more numerous than histiocytes
Histiocytoma
Cutaneous Histiocytosis (dogs)
• Single mass or multiple masses
• May regress spontaneously
• May wax and wane over years, requiring
multiple surgeries or immunosuppressive
therapy
• Prednisone 2 mg/kg PO SID, and taper as
signs regress over 2-3 months
• Cyclosporine 5 mg/kg PO SID-BID, taper
• Leflunomide 2-4 mg/kg PO SID
• Goal is trough level 20 mcg/ml, taper
• Side effect vomiting
Systemic Histiocytosis
• Familial in Bernese Mountain
Dog
• Slowly progressive disease
• Cutaneous masses
• Sometimes other organs are
affected
• Localized histiocytic sarcoma
• Also retrievers and
Rottweilers
• Nodules occur around and
infiltrate joints
Malignant Histiocytosis
• Multi-system, rapidly progressive disease
• Bernese Mountain dogs, retrievers,
Rottweilers
• Histiocytic infiltration of spleen, lymph
nodes, lung, bone marrow, skin
• Usually leads to death in weeks
• Clinical signs
• Weight loss, lethargy, anorexia
• Coughing, dyspnea
• Seizures, weakness, lameness
• No effective treatment
TVT
• The only known naturally occurring tumor
that can be transplanted as an allograft
• Transmitted by transplantation of cells
onto abraded mucous membranes
• During breeding
• Nose to butt contact
• In the nose, on the perineum, or on/in the
reproductive tract
• Begins as hyperemic papules
• Progresses to multilobulated, ulcerated,
bleeding mass
TVT
• If untreated, can metastasize
• Eye, skin, lips, oral and nasal cavities
• Regional lymph nodes
• Lungs, liver, brain
• Abnormal karyotype with 59 chromosomes
• Dogs normally have 78
• May occasionally spontaneously regress
• Usually recur if surgically removed
TVT
Treatment
• Vincristine 0.7 mg/m2 IV weekly
• Continue 2-3 weeks past resolution of
disease
• Usually 3-5 injections are required
• If no response, doxorubicin 30 mg/m2 IV
q3 weeks x 3 treatments
• Radiation is also effective, but often
reserved for those that do not respond to
chemotherapy
• Spay-neuter and do not allow to roam
TVT
TVT
TVT
TVT
Round Cell Tumor Cytology
• Covered Lymphoid Cells
• Histiocyte – larger than lymphoblast
• Round to indented nucleus
• Scant to Moderate pale cytoplasm
• Mast Cell – histiocyte w/ purple granules
• TVT – histiocyte with clear vacuoles
• Plasma Cells
• Dark blue cytoplasm with central pallor
• Perinuclear clear zone (Golgi zone)
• Eccentric nucleus
Cytology
• Rottweiler, sick with enlarged lymph nodes,
spleen and liver – LN cytology
• Dx – large cell lymphoma
Cytology
• Button like alopecic skin mass
Cytology
• Button like alopecic skin mass
• Dx - Plasmacytoma
Cytology
• Button like alopecic tumor
• Dx – mast cell tumor
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Cytology
• Golden Retriever, sick with enlarged lymph
nodes, spleen and liver
• Dx – malignant histiocytosis
Cytology
• Recurring button like alopecic masses
• Dx – cutaneous histiocytosis
Cytology
• alopecic tumor protruding from the naris,
bleeds when bumped
• Dx – TVT
Cytology
• Infiltrative plaque-like skin masses
• Dx – Multiple Myeloma