[Fetal rhabdomyomatous nephroblastoma: study of 2 cases and review of the literature].

Report of two cases of Fetal Rhabdomyomatous Nephroblastoma, a cytodifferentiated variant of Wilms' tumor. The incidence of this rare variant is of 2.10% in our material (88 nephroblastomas in a sixteen years period). The patients were ten months and two years old. Bilateral tumors were discovered in both patients. Preoperative radiotherapy was given but no reduction of the tumors size was obtained. Microscopically, benign looking striated muscle is the predominant component of the tumors, with scare foci of epithelial elements. The low age of presentation, high incidence of bilaterality and the peculiar intrapelvic renal growth are three relevant characteristics in the 35 cases previously reported as well as in these two new cases, that distinguish Fetal Rhabdomyomatous Nephroblastoma from conventional Wilms' tumor.