[Primary primitive neuroectodermal tumor of the kidney in an adult. Clinico-pathologic and immunohistochemical case report].

We report a case of a primary renal primitive neuroectodermal tumour in a 24-year-old man associated with multiple pulmonary metastases. Histologically, the bulk of the kidney was replaced by a small round-cell tumour with numerous true Homer-Wright rosettes and perivascular pseudorosettes; wide-spread vascular invasion was noted. There was no evidence at autopsy of a primary tumour elsewhere. Immunohistochemically, the tumour cells stained strongly positive for O-13, a monoclonal antibody, which recognizes a recently described cell membrane glycoprotein (p30/32MIC2), more weakly for NSE and at least focally for PGP 9.5; the tumour did not stain for other neural markers, cytokeratin, leucocyte common antigen, or desmin. The differential diagnosis of small round-cell tumours in this location and the relation of primitive neuroectodermal tumours and Ewing's sarcoma are discussed.