Cellular Neurothekeoma with Atypical Histologic Features in the Thigh: A Case Report

Abstract

Neurothekeoma is a rare, benign neoplastic process that most commonly presents on the head and neck of young adults. We report a case of cellular neurothekeoma in a middle-aged woman with a thigh lesion showing histologic features that closely mimicked malignant tumors, particularly undifferentiated pleomorphic sarcoma, sarcomatoid carcinoma, and amelanotic melanoma. A dermal/subcutaneous thigh lesion demonstrated marked cytologic atypia and an infiltrative growth pattern on histologic evaluation. Immunohistochemistry supported the diagnosis of cellular neurothekeoma: tumor cells were positive for CD10 and showed very focal MITF staining, and negative for S100, SOX10, desmin, EMA, AE1/AE3, SMA, NSE, and factor XIIIa. The lesion was completely excised with clear margins. At 12 months of clinical follow-up, no recurrence was observed. Cellular neurothekeoma should be considered in the differential diagnosis of atypical dermal soft-tissue masses with worrisome histologic features. Ancillary studies, particularly immunohistochemistry, are essential to exclude aggressive mimics and avoid overtreatment, although conclusions remain limited by the single-case nature of this report and the available literature.