PATHOPHYSIOLOGY


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 FEATURES


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


Treatment


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

 

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