Malignant Melanoma of the Vulva and Vagina: A US Population-Based Study of 1863 Patients

Background Vulvar melanoma (VuM) and vaginal melanoma (VaM) represent a unique subgroup of malignant melanomas with important differences in biology and treatment. Objective The objective of this study was to describe the epidemiology and prognosis of VuM and VaM in a large representative cohort. Methods Women with invasive VuM or VaM were identified from the Surveillance, Epidemiology and End Results-18 population representing 27.8% of the US population. Data on age, ethnicity, stage, location, histopathology, primary surgery, and lymphadenectomy were collected. The Kaplan-Meier method was used to analyze disease-specific and overall survival. Univariate and multivariate regression models were used to identify factors with a significant association with disease-specific survival. Results A total of 1400 VuM and 463 VaM were included for further analysis; 78.6% and 49.7% of women with VuM and VaM underwent surgery, but only 52.9% of women with non-metastatic VuM and 42.9% of women with non-metastatic VaM undergoing surgery had lymph node assessment; one third of these had positive nodes. Superficial spreading was the most common subtype in VuM, and nodular melanoma in VaM (p < 0.001). The median disease-specific survival was 99 months (95% confidence interval 60-138) and 19 months (95% confidence interval 16-22), respectively. Survival was significantly associated with age at diagnosis, ethnicity, stage, surgery, lymph node metastases, histologic subtype, ulceration, mitotic count, and tumor thickness in VuM, and stage, surgery, and lymph node involvement in VaM. In the Cox model, lymph node status and number of mitoses remained independent predictors of outcome in VuM; in VaM, only lymph node status remained significant. Conclusions The overall prognosis of VuM and VaM remains poor. The American Joint Committee on Cancer staging system is applicable and should be used for VuM; however, lymph node status and mitotic rate are the most important predictors of survival. Lymph node status should be assessed and patients with positive nodes may be candidates for adjuvant treatment.