PATHOPHYSIOLOGY

General Considerations

•penile tumors account for 0.24% of all tumors in male dogs

•SCC and transmissible venereal tumor most common are the most common tumors of the penis and prepuce

•other types include MCT, LSA, FSA, histiocytic reticulocytoma, TCC, CSA, fibroma, and papilloma

•LSA has been reported in association with penile prolapse in 1 dog

•OSA, osteoma, and multilobular osteochondrosarcoma have been reported in the os penis

•leishmaniasis can cause nodular penile mucosal lesions

•penile tumors usually occur in older dogs

•transmissible venereal tumors occurs in 4-5-year-old dogs with increased risk in free roaming dogs

•transmissible venereal tumors are transmitted by contact with genital mucous membranes during coitus

•transmissible venereal tumors appear as multiple tumors along the penis and mucosal lining of the prepuce

CLINICAL FEATURES

Clinical Signs

•preputial enlargement with frequent licking of the penis and prepuce

•stranguria, dysuria, and hematuria

•serosanguineous or hemorrhagic preputial discharge as most tumors are friable and bleed easily

•painful

•± urethral obstruction

Diagnosis

•physical examination

•cytology from FNA or impression smear

•histopathology from incisional or excisional biopsy

Treatment

•partial penile amputation

•total penile amputation with scrotal urethrostomy ± penile urethrostomy if tumor extends into the proximal urethra

•ventral midline preputiotomy for penile tumors that are large enough to allow penile extrusion through the preputial orifice (preputial splitting)

•local tumor recurrence rate is high for dogs with transmissible venereal tumor and surgery is not recommended

•transmissible venereal tumors are very response to chemotherapy and radiation therapy

•chemotherapy: vincristine 0.5-0.7 mg/m 2 IV 4-8 times ± doxorubicin