Overview

• Second most common reproductive tumor, comprising 2.4–3% of all tumors in dogs.
• Dogs-86% benign smooth muscle tumors, often pedunculated (e.g., leiomyoma, fibroleiomyoma, and fibroma); lipoma, transmissible venereal tumor, mast cell tumor, squamous cell carcinoma, leiomyosarcoma, hemangiosarcoma, osteosarcoma, or extension of primary urinary tract carcinomas also reported.
• Dogs-may be an incidental finding at necropsy.
• Cats-extremely rare; usually of smooth muscle origin.
• Hormonal influence-may play a role in the development of leiomyomas, fibromas, or polypoid tumors.

Signalment

• Dog-mean age, 10.2–11.2 years, boxers, nulliparous bitches.
• Cat-no data available.

Signs

Causes & Risk Factors

• Intact sexual status (hormonal influence)
• Nulliparous bitches more commonly affected

Differential Diagnosis

• Vaginal prolapse
• Urethral neoplasia
• Uterine prolapse
• Clitoral hypertrophy
• Vaginal polyp
• Vaginal abscess/granuloma
• Vaginal hematoma

CBC/Biochemistry/Urinalysis

No consistent abnormalities

Other Laboratory Tests

N/A

Imaging

• Thoracic radiography-recommended; assess for pulmonary metastatic disease.
• Abdominal radiography-may detect cranial extension of a mass.
• Ultrasonography, vaginography, and urethrocystography-may help delineate mass.
• CT/MRI-definitive delineation of tumor, assess for surgical feasibility, assess for metastatic disease.

Diagnostic Procedures

• Vaginoscopy with cytologic examination of an aspirate-may help determine cell type.
• Biopsy with histopathologic examination-often necessary for definitive diagnosis.

Pathologic Findings

• Intraluminal-vestibular wall; protruding into the vulva; may occur singularly or as multiple masses.
• Extraluminal-vestibular roof; causing a bulging of the perineum.

Drug(s)

• Postoperative therapy-no standard established.
• Doxorubicin, cisplatin, or carboplatin-rational choice to palliate malignant or metastatic disease.
• Piroxicam may be useful especially for those dogs with primary urinary tumors extending into the vagina and carcinomas.

Contraindications/Possible Interactions

• Doxorubicin-carefully monitor with underlying cardiac disease; consider pretreatment and serial echocardiograms and ECG.
• Cisplatin-do not use in cats (fatal); do not use in dogs with renal disease; always use appropriate and concurrent diuresis.
• Chemotherapy may be toxic; seek advice if you are unfamiliar with chemotherapeutic drugs.
• Piroxicam should not be used with other NSAIDs or prednisone and should be avoided in animals with underlying renal or hepatic disease. Should not be used in conjunction with cisplatin.

Patient Monitoring

• Thoracic and abdominal radiography-consider every 3 months if tumor is malignant.
• CBC (doxorubicin, cisplatin, carboplatin), biochemical profile (cisplatin, piroxicam), urinalysis (cisplatin, piroxicam)-perform before each chemotherapy treatment.

Expected Course and Prognosis

• Prognosis-good with complete excision; guarded if incomplete excision; poor with metastatic disease; poor with carcinoma or squamous cell tumor.
• Recurrence-15% (leiomyoma) without concurrent ovariohysterectomy.

Associated Conditions

Cats-reported concurrent cystic ovaries and mammary gland adenocarcinoma.

Abbreviations

• CT = computed tomography
• ECG = electrocardiogram
• MRI = magnetic resonance imaging
• NSAID = nonsteroidal anti-inflammatory drug