EXTRARENAL WILMS-TUMOR - AN ULTRASTRUCTURAL AND IMMUNOELECTRON MICROSCOPIC CASE-REPORT

Wilms' tumor is the most common malignancy of the genitourinary tract in children but the occurrence of extrarenal Wilms' tumor is extremely rare. Extrarenal Wilms' tumor, which by definition excludes a primary tumor in the kidney, has been reported less than fifty times. The ult rastructural appearance of renal Wilms' tumor has been well documented , but the present report is believed to be the first description of th e ultrastructural appearance of extrarenal Wilms' tumor. The authors r eport, for the first time, localization of intermediate filament prote ins (vimentin and cytokeratin) and epithelial membrane antigen (EMA) b y immunoelectron microscopy in this neoplasm. Demonstration of the coe xpression of vimentin and cytokeratin within the same blastemal cell, as well as the identification of desmosomes in a cell with vimentin in termediate filaments, suggests a relationship between stroma, blastema , and epithelia similar to that proposed in renal Wilms' tumor.