Recent advances in pediatric renal neoplasia.

Over the past 6 years, molecular genetic studies have significantly advanced our understanding of pediatric renal neoplasms. The cellular variant of congenital mesoblastic nephroma (but not the classic variant) has been shown to bear the same t(12;15)(p13;q25) and ETV6-NTRK3 gene fusion as infantile fibrosarcoma, a tumor with which it shares morphologic and clinical features. Rhabdoid tumor of the kidney is characterized by deletion of the hSNF5/INI1 gene, which links it to other rhabdoid tumors of infancy that arise in the soft tissue and brain. Primary renal synovial sarcomas and renal primitive neuroectodermal tumors have become accepted entities, and likely comprise a subset of what had previously been termed "adult Wilms tumor." Renal carcinomas associated with Xp11.2 translocations that result in fusions involving the TFE3 transcription factor gene have been delineated, including a distinctive neoplasm that shares the identical gene fusion as alveolar soft part sarcoma. Most recently, a distinctive type of renal neoplasm with a t(6;11)(p21;q12) has been described, and the cloning of the resulting gene fusion links it to the Xp11 translocation carcinomas. Together, these last two translocation-associated tumors represent a significant proportion of pediatric renal cell carcinomas. This review highlights each of these recent advances.