A case of primitive neuroectodermal tumor that arose from subcutaneous tissue of the buttock

Primitive neuroectodermal tumors (PNETs) are malignant, round-cell sarcomas which exhibit primitive neuronal differentiation. They usually arise in deep soft tissues, but occasionally bones and visceral organs are affected. In general, PNET presents as rapidly-growing, deeply located masses measuring 5-10 cm at their greatest diameter. Superficially located cases do occur but are rare. The typical PNET is composed of sheets or lobules of small round cells containing darkly-staining, round or oval nuclei. The cytoplasm is indistinct except in areas where the cells are more mature and elongated hair-like cytoplasmic extensions coalesce to form rosettes. We herein report a case of PNET that arose from subcutaneous tissue of the buttock in a 31-year-old woman.