Myoepithelioma-like Tumor of the Vulvar Region: A Three-Case Series and Literature Review

Context.— Myoepithelioma-like tumor of the vulvar region (MELTVR) is a rare SMARCB1/INI1 -deficient mesenchymal tumor affecting young and middle-aged women. Objective.— To better characterize this rare and novel tumor to enhance understanding and draw clinical attention. Design.— The clinical, immunohistochemical, and molecular features of three cases of myoepithelioma-like tumors of the vulvar region from our hospital were analyzed. Results.— Three patients (aged 27–33 years) presented with incidental subcutaneous nodules in the vulva (1 case) or the mons pubis (2 cases). One patient experienced rapid tumor enlargement during pregnancy. Histopathologically, the tumors were composed of short spindled to epithelioid cells with relatively uniform nuclei and faintly eosinophilic to amphophilic cytoplasm. Mitotic activity was low (1–2 figures per 10 high-power fields [HPFs]). Focal fat infiltration was seen in individual cases. Immunohistochemically, the tumors were positive for vimentin and epithelial membrane antigen, while cytokeratin was negative or focally positive. Estrogen receptor and progesterone receptor were diffusely positive. Smooth muscle actin was focally positive or negative. Tumors were negative for CD34, S100 protein, and desmin. SMARCB1/INI1 expression was lost in every case. In one instance, next-generation sequencing analysis showed no signs of NR4A3, FUS , or EWSR1 gene rearrangements. All patients underwent wide local excision. One patient experienced local recurrence in 1 year; currently, all are free of disease. Conclusions.— MELTVRs generally follow an indolent course with rare recurrences. Complete surgical excision with clear margins is associated with a favorable prognosis. However, owing to the limited reports on MELTVRs at present, more cases and longer-term follow-up data are needed to further elucidate their biological behavior.