Concurrent Vulvar and Cutaneous Melanoma in a 40-Year-Old Woman: A Rare Case of Multiple Primary Melanomas.

Background: Vulvar melanoma is a rare but aggressive malignancy associated with worse survival outcomes than cutaneous melanoma and significant diagnostic and therapeutic challenges. Multiple primary melanomas (MPMs) occur in a minority of patients and require careful distinction from metastatic disease, as management strategies differ substantially. Concurrent mucosal and cutaneous primaries in a young patient are particularly uncommon. Case Presentation: A 40-year-old woman undergoing routine gynecologic screening was found to have multifocal pigmented lesions of the vulva. Biopsies confirmed melanoma in situ (MIS) with pagetoid spread. Staging PET/CT showed no metastatic disease. Dermatologic examination identified a separate 6 mm superficial spreading melanoma of the left buttock (Breslow 0.3 mm, pT1a). Clinical, histopathologic, and imaging features supported classification as two synchronous primary melanomas rather than metastatic disease. The patient underwent bilateral modified radical vulvectomy with sentinel lymph node biopsy; final pathology demonstrated pT1b vulvar melanoma (0.9 mm) with negative nodes but positive central margins, requiring re-excision. Subsequent biopsies revealed additional MIS managed with Mohs micrographic surgery, which confirmed clear margins. Comprehensive germline panel testing of 27 hereditary cancer genes identified no pathogenic variants. The patient was initiated on intensified multidisciplinary surveillance adapted from NCCN stage IIB cutaneous melanoma guidelines. Conclusion: This case highlights the diagnostic complexity and management challenges of synchronous mucosal and cutaneous melanomas in a young patient. Multifocal vulvar disease complicates margin control and may warrant selective use of Mohs micrographic surgery to preserve anatomy while achieving clearance. Given the poorer prognosis associated with vulvar melanoma and MPMs, coordinated multidisciplinary care and structured long-term surveillance are essential. Further research is needed to refine risk stratification and develop integrated management guidelines for these uncommon but high-risk presentations.