Abstract

A 19-year-old male presented to his primary care manager with a two week history of a tender lesion on his right thigh. The patient reported trauma as a possible inciting event. Physical exam revealed an isolated 2cm erythematous, firm, tender, domed papule on the right lateral thigh. An infectious abscess was suspected and incision and drainage was attempted. Upon incision of the lesion, a fatty substance was discovered and the procedure was aborted. The dermatology clinic was contacted for evaluation of a suspected lipoma. Upon presentation to our clinic, the above lesion was identified with a 1cm overlying incision with hemorrhagic crust. Intraoperatively, shave biopsy revealed an underlying encapsulated adipose tumor. The procedure was then converted to a narrow excision and the residual mass was easily dissected and removed. Pathologic evaluation of the tissue showed a highly cellular neoplasm with irregular vesicular nuclei, prominent nucleoli, and multifocally scattered mitoses. The cells demonstrated a palely eosinophilic to amphophilic cytoplasm with concentric growth around vascular channels. Staining of the lesion revealed multifocal weak staining for EMA and strong positivity for SMA, with negative staining for pan-keratin, S100, SOX10, ALK, CD30, CD34, CAM5.2, and desmin. The architecture and staining pattern of the lesion was most consistent with a diagnosis of malignant myopericytoma, an exceedingly rare malignancy with less than 10 cases reported in the English literature.

Financial Disclosure:
No current or relevant financial relationships exist.