Sarcomatous renal tumor of childhood. An electron microscopic study

A review of 106 cases of Wilms' tumor revealed five examples of a distinctive, monomorphic, sarcomatous renal tumor. Electron microscopic studies suggested that such tumors have their origin from the blastemal cap cells of the developing metanephros. These variants of Wilms' tumor are more likely to metastasize to bone and have a poorer prognosis than the usual type of nephroblastoma.