Primary Extraosseous Ewing Sarcoma of the Vulva: Unravelling the Mystery of a Common Tumor in an Uncommon Site.

Primary vulvar Ewing sarcoma (ES) is exceedingly rare, particularly in postmenopausal women. To date, only 14 cases have been confirmed through molecular cytogenetic analysis. We report the case of a 55-year-old woman presenting with a painful, ulcerated vulvar mass. Imaging revealed a 6×7.9×8.5 cm lobulated soft tissue lesion. Contrast-enhanced computed tomography (CECT) demonstrated pulmonary metastases. Histopathology of the vulvar mass showed sheets of malignant small round cells, which were highlighted by strong membranous CD99 expression and NKX2.2 nuclear expression on immunohistochemistry. Fluorescence in situ hybridization (FISH) using a break-apart probe confirmed EWSR1 gene rearrangement, establishing the diagnosis of ES. Despite receiving eight cycles of chemotherapy, the patient succumbed to the disease. This is the 15th reported case of primary vulvar ES with molecular confirmation. The case highlights the importance of considering ES in the differential diagnosis of vulvar tumors and underscores the value of molecular diagnostics in guiding management.