Epithelioid malignant peripheral nerve sheath tumor of the uterine corpus.

Epithelioid variant of a malignant peripheral nerve sheath tumor (MPNST) is a rare sarcoma. Rarer still is its occurrence at uncommon sites like the uterine corpus where an index of suspicion for this diagnosis is extremely low. Herein, we report a rare case of a uterine epithelioid MPNST in a young girl who underwent a total abdominal hysterectomy for a uterine tumor that was initially diagnosed as an undifferentiated sarcoma and whose paraffin blocks were submitted to us for review. Biopsy sections showed a malignant tumor, predominantly composed of polygonal cells, including "rhabdoid" forms with conspicuous mitoses. On immunohistochemistry, tumor cells were diffusely positive for vimentin and S-100 and negative for smooth muscle actin, desmin, myogenin cytokeratin, epithelial membrane antigen, melan A, HMB-45, CD10, glial fibrillary acid protein inhibin, synaptophysin, chromogranin, MIC2, FLI-1, and neuron-specific enolase. Diagnosis of an epithelioid MPNST was offered. The case is presented in view of its rarity and also to highlight the value of immunohistochemistry in objectively identifying unusual sarcomas at uncommon sites.