Malignant vulvar melanoma (VuM) and vaginal melanoma (VaM) represent a unique subgroup of rare malignant melanomas with critical biological properties that differ from other cancers. In Japan, adequate surveys have yet to be conducted. This study aimed to elucidate the clinicopathological demographics and outcomes of VuM and VaM in Japan. This retrospective observational study included women with invasive VuM or VaM identified from older medical records in Japan. We collected clinical data and used the Kaplan-Meier method to analyze progression-free survival (PFS) and overall survival (OS). Univariate and multivariate regression models were used to identify factors significantly related to survival. We identified 217 patients, 109 (50.2%) with VuM and 108 (49.8%) with VaM. The median PFS was 16.8 months in patients with VuM [95% confidence interval (CI), 23.1-87.7] and 15.6 months in those with VaM (95% CI, 8.4-12.6). The median OS was 43.9 months (95% CI, 60-138) and 31.1 months (95% CI, 24.8-45.3) in patients with VuM and VaM, respectively. Multivariate analysis showed that a disease stage higher than stage III, based on the American Joint Committee on Cancer (AJCC) guidelines, was associated with poorer PFS [hazard ratio (HR), 2.063; 95% CI, 0.995-4.278] and an unknown surgical margin was the only independent factor influencing OS (HR, 2.188; 95% CI, 1.203-3.977). The overall outcomes of invasive VuM and VaM in Japan remain poor. AJCC staging and surgical margins were significant predictors of survival.
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