Overview

• Sexually, or other direct contact, transmitted, naturally occurring tumor.
• Appears to be more common in temperate areas and large cities.

Signalment

Intact dogs of either sex

Signs

• Red, friable, lobulated mass on the mucosa of the vagina, penis or other mucous membranes.
• Oral mucosa may be affected.
• Owners may report blood dripping from the affected area or excessive licking of the genital area.
• Tumor protrusion may be noticed.

Causes & Risk Factors

• Direct transplantation of tumor cells onto abraded mucosa, either by coitus or oral transmission.
• Intact, free-roaming dogs are at greater than average risk.

Differential Diagnosis

• Other neoplasia (e.g., squamous cell carcinoma, cutaneous lymphoma).
• Vaginal hyperplasia.

CBC/Biochemistry/Urinalysis

• Usually unremarkable.
• Urinalysis (free-catch) reveals hematuria and abnormal cells in some patients if the tumor is within the urogenital tract.

Other Laboratory Tests

N/A

Imaging

• Thoracic radiographs, although this tumor type is rarely metastatic.
• Abdominal ultrasonography to evaluate mesenteric lymph nodes.

Diagnostic Procedures

• Careful palpation of regional lymph nodes, and perform aspirates with cytology when clinically indicated.
• Examination of impression smears or aspirates of the tumor reveals homogenous sheets of round to oval cells with prominent nucleoli, scant cytoplasm, and multiple clear cytoplasmic vacuoles.
• Biopsy offers definitive diagnosis.

Drug(s)

• Vincristine sulfate (0.5–0.7 mg/m² IV once weekly for 2 weeks beyond complete resolution of gross disease).
• If only partial or no remission, doxorubicin (30 mg/m² IV every 3 weeks) may be tried.

Contraindications/Possible Interactions

• Myelosuppression secondary to vincristine or doxorubicin administration.
• Doxorubicin may be cardiotoxic, use with caution once a cumulative dose of 150 mg/m² is reached.
• Tissue sloughing if either vincristine or doxorubicin is administered perivascularly.
• Seek advice before initiating therapy if unfamiliar with cytotoxic drugs.

Patient Monitoring

CBC and platelet count before each chemotherapy treatment.

Prevention/Avoidance

• Neuter animals
• Prevent animals from roaming free

Possible Complications

• Tumor recurrence possible following incomplete surgical excision or re-exposure.
• Metastatic disease uncommon, but reported to occur in regional lymph nodes, eye, and spinal cord.

Expected Course and Prognosis

Most cases of TVT have an excellent response to therapy (primarily chemotherapy or radiotherapy) and an excellent prognosis.

Zoonotic Potential

None

Pregnancy/Fertility/Breeding

• Pregnant animals should not be treated with chemotherapy.
• Animals may be infected with TVT during coitus.

Abbreviation

TVT = transmissible venereal tumor