Vaginal Tumors

+ General Considerations

• Vaginal and vulval tumors are the 2nd most common canine reproductive tumor and account for 2.4%-3.0% of all canine tumors
• Majority of vaginal and vulval tumors are benign:
• Leiomyoma and fibroma in cat
• Leiomyoma and lipoma in dog

+ Leiomyoma

• 86% of vaginal and vulvar tumors are benign smooth muscle tumors (i.e., leiomyoma and fibroma)
• Majority of leiomyomas arise from vestibule of vulva rather than vagina
• Extraluminal and intraluminal forms have been described:
• Extraluminal present with a slow-growing perineal mass
• Intraluminal are attached to vestibular or vaginal wall by variably sized pedicle and can be multiple
• Mucosa is generally intact but ulceration may occur with exposure and irritation
• Leiomyoma may be hormone dependent:
• Leiomyoma has not been diagnosed in dogs ovariectomized < 2 years
• 15% local tumor recurrence rate in intact and 0% in dogs following ovariohysterectomy
• Mean age 10.8 years
• Breed predisposition: Boxer
• Incidence of leiomyoma higher in nulliparous bitches
• 33% associated with cystic endometrial hyperplasia, ovarian cysts, and mammary gland tumors

+ Lipoma

• Lipoma can arise from perivascular or perivaginal adipose tissue and attach to tuber ischii
• Lipoma can lie within pelvic canal and are usually well-circumscribed and relatively avascular
• Mean age 6.3 years

+ Transmissible Venereal Tumor

• Transmissible venereal tumors occurs in 4-5-year-old dogs with increased risk in free roaming dogs
• Cell origin of transmissible venereal tumors is unknown, but an undifferentiated round cell tumor of reticuloendothelial origin is most likely
• Transmissible venereal tumors have a common origin as chromosomal aberrations are constant and highly specific
• Virus particles have been identified in transmissible venereal tumors
• However, viral etiology is unlikely as the disease cannot be transmitted by cell-free filtrates
• Transmissible venereal tumors are transmitted by contact with genital mucous membranes during coitus
• Transmissible venereal tumors appear as multiple tumors along the mucosal lining of the vagina and vestibule

+ Other

• Benign tumors: sebaceous adenoma, fibrous histiocytoma, benign melanoma, myxoma, and myxofibroma
• Malignant tumors: leiomyosarcoma, ADC, SCC, TCC, HSA, OSA, MCT, and epidermoid carcinoma
• Carcinoma of bladder or urethra may present with palpably enlarged urethral papilla

+ Clinical Signs

• Duration of clinical signs longer for extraluminal compared to intraluminal leiomyoma
• Intraluminal leiomyoma often presents as mass extruding between vulval lips, particularly during estrous
• Other clinical signs include vulval bleeding or discharge, enlarging vulvar mass, dysuria, hematuria, tenesmus, excessive vulval licking, and dystocia
• Lipomas usually present with a slowly growing mass impinging on adjacent structures

+ Diagnosis

• Vaginoscopic examination, retrograde vaginography, and urethrocystography may delineate mass
• Ultrasonography, FNA, and histopathology

+ Medical Management

• 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

+ Surgical Management – Benign Tumors

• Exploratory celiotomy for ovariohysterectomy (due to hormonal dependence and local tumor recurrence)
• Conservative surgical resection
• Wide resection probably not required if ovariohysterectomy performed concurrently
• Dorsal episiotomy may be required to provide adequate visualization and ensure complete resection
• Dorsal episiotomy indicated for extraluminal vaginal and vulvar tumors as tumors are usually well-circumscribed and poorly vascularized resulting in good probability of complete excision
• Perineal approach or pubic split is rarely required

+ Surgical Management – Malignant Tumors

• Malignant infiltrative vaginal tumors treated with complete vulvovaginectomy and perineal urethrostomy
• Sternal recumbency in perineal stand with perineum elevated
• Urethra catheterized
• Fusiform skin incision performed around vulva
• Deeper tissues sharply dissected from labia and vestibule
• Constrictor vestibuli and constrictor vulvae muscles are dissected from the vestibule
• Dorsal labial branches of the ventral perineal artery are ligated or bleeding controlled with electrocautery
• Catheterized urethra identified and dissected free from encircling constrictor vestibuli muscles

From: Bilbrey SA, et al: Vulvovaginectomy and perineal urethrostomy for neoplasms of the vulva and vagina. Vet Surg 18:450-453, 1989.

• Vagina dissected with transection of ischiocavernosus and ischiourethralis muscles
• Dissection continued cranially between paired levator ani muscles to level of cervix
• Vaginal branches of vaginal and uterine arteries and veins ligated
• Vagina transected immediately caudal to cervix in intact bitches or cervix and uterine stump removed in spayed dogs
• Deep tissues closed to reduce dead space
• Perineal urethrostomy performed with transected urethra tractioned caudally, distal end spatulated, and closed in 2 layers with final layer mucosa to skin

From: Bilbrey SA, et al: Vulvovaginectomy and perineal urethrostomy for neoplasms of the vulva and vagina. Vet Surg 18:450-453, 1989.

+ Prognosis

• Complete surgical excision is usually curative
• Guarded to poor prognosis with ADC, TCC, and SCC due to high local tumor recurrence and metastatic rates