Pediatric Renal Tumors: Diagnostic Updates

Abstract

Pediatric renal tumors are rare, and share very little overlap with adult renal tumors. By far, the most common is Wilms tumor, a triphasic tumor with an average presentation of 2–5 years of age and a very good prognosis. Unfavorable histology in Wilms tumor is a marker of adverse prognosis, and is defined by diffuse anaplasia. Congenital mesoblastic nephroma is a spindle cell tumor found almost exclusively in infants. The cellular variant has a characteristic t(12;15) ETV6–NTRK3 rearrangement. Clear cell sarcoma of the kidney has variable histology, and has been recently described to often have BCL6 corepressor (BCOR) internal tandem duplication repeats. Rhabdoid tumor has characteristic rhabdoid morphology and loss of INI1 staining by immunohistochemistry, a surrogate marker for SMARCB1 inactivation. Renal carcinomas are very rare in the pediatric population, but may be seen. These include MiT-translocation associated renal cell carcinomas; positive immunohistochemistry for TFE3 is a surrogate for the characteristic translocations. Renal medullary carcinomas are very aggressive tumors found almost exclusively in patients with sickle cell trait; INI1 loss by immunohistochemistry is characteristic. Two pediatric renal tumors are related to alterations in DICER1: cystic nephroma and anaplastic sarcoma of kidney. Ossifying renal tumor of infancy is a very rare, benign kidney tumor seen almost exclusively in infants.