Fetal rhabdomyomatous nephroblastoma. Pathologic histology and special clinical and biologic features.

Fetal rhabdomyomatous nephroblastoma is a very rare variant of Wilms' tumor. The special clinical and histologic features of this variant are presented on the basis of a case seen in a boy who was 13 months old at nephrectomy 8 months ago and has remained healthy since then. The tumor chiefly consists of fetal striated muscle; it occurs predominantly in infancy and early childhood and is often bilateral. Angiography shows a relative paucity of vessels. The volume of the tumor (determined by ultrasonography) decreases only slightly after preoperative radio- and chemotherapy because of a predominance of mesenchymal structures. The finding of nodular renal blastema in renal parenchyma with an …