Peripheral neuroepithelioma: a light and electron microscopic study.

A primitive neuroectodermal tumor of peripheral nerve origin was examined by light and electron microscopy. The lesion arose in association with the S1 nerve root of the lumbosacral plexus in a 22-year-old female. Following a surgical biopsy, the patient received systemic chemotherapy; however, approximately one-and-a-half years later, she suffered a clinical relapse with locally recurrent tumor. An excisional biopsy was performed, and pathologic examination revealed progressive neuroblastic differentiation. The ultrastructural features of neoplastic Homer-Wright rosettes will be illustrated, and the non-specificity of cytoplasmic glycogen in the evaluation of "small round cell neoplasms" will be emphasized.