Primary rhabdomyosarcoma of the kidney. A light microscopic, immunohistochemical, and electron microscopic study.

Primary rhabdomyosarcoma of the kidney is a rare and highly aggressive tumor in the adult population. A case is reported in a 70-year-old woman with the diagnosis confirmed by immunohistochemistry and electron microscopy. This is the first case studied using the immunoperoxidase technique and the second with electron microscopic examination. To make a diagnosis of primary sarcoma, of the kidney, three criteria must be met: (1) a metastatic sarcoma must be ruled out; (2) the tumor must arise from renal parenchyma; and (3) a sarcomatoid variant of renal cell carcinoma needs to be excluded. The literature is reviewed and available clinical and pathologic details are summarized.