Cancer found in the vagina is most likely metastatic disease. Primary vaginal carcinoma is rare and makes up less than 5 percent of all gynecologic malignancies (Siegel, 2019). This low incidence reflects the infrequency with which primary carcinoma arises in the vagina and the strict criteria for its diagnosis. According to International Federation of Gynecology and Obstetrics (FIGO) staging criteria, a vaginal lesion that involves adjacent organs such as the cervix or vulva, by convention, is deemed primary cervical or vulvar, respectively (Pecorelli, 1999). The most common histologic type of primary vaginal cancer is squamous cell carcinoma, followed by adenocarcinoma (Platz, 1995).
During embryogenesis, the müllerian ducts fuse caudally to form the uterovaginal canal (Chap. 18). The canal’s distal portion forms the proximal vagina, whereas the distal vagina arises from the urogenital sinus. The uterovaginal canal is lined by columnar epithelium, which is subsequently replaced by squamous cells migrating cephalad from the urogenital sinus. These squamous cells stratify, and the vaginal epithelium matures and thickens. Underlying this epithelium, muscularis and adventitial layers surround the vaginal tube.
With vaginal cancer, local extension and lymphatic invasion are common patterns of spread. The lymphatic channels that drain the vagina form extensive, complex, and variable anastomoses. As a result, any node in the pelvis, groin, or anorectal area may drain any part of the vagina. Of these, the external, internal, and common iliac lymph nodes are the primary sites of vaginal lymphatic drainage. Thus, pelvic lymphadenectomy, which samples these nodal groups, is commonly performed during primary surgical excision of proximally located vaginal cancers. Alternatively, lymphatic vessels of the posterior vagina may empty into the inferior gluteal, presacral, or perirectal nodes, and those of the vagina’s distal third may drain to the superficial and deep inguinal lymph nodes (Frank, 2005).
Hematogenous spread of vaginal cancer is less frequent, and venous drainage consists of the uterine, pudendal, and rectal veins, which drain into the internal iliac vein. Arterial blood supply to the vagina comes primarily from internal iliac artery branches, which include the uterine, vaginal, middle rectal, and internal pudendal arteries (Fig. 38-12).
According to estimates for 2019, approximately 5000 new cases of vaginal cancer will be diagnosed in the United States, and there will be 1430 deaths (Siegel, 2019). The overall incidence is 0.45 cases per 100,000 women but is notably lower in whites (0.42 cases) compared with black and Hispanic women (0.73 and 0.56 cases, respectively) (Watson, 2009). Vaginal cancer rates rise with age and peak among women aged ≥80 years. The median age at diagnosis is 58 (Watson, 2009). Of histologic forms, squamous cell carcinoma accounts for 70 to 80 percent of all primary vaginal cancer cases (Beller, 2003; Ghia, 2011).