KIT expression in normal and neoplastic renal tissues: immunohistochemical and molecular genetic analysis.

Renal chromophobe cell carcinomas (ChCC) and oncocytomas express KIT. This character seems to reflect their common histogenesis from distal nephrons. In the normal kidney, however, the expression and localization of KIT are unclear. KIT expression in angiomyolipoma and congenital mesoblastic nephroma (CMN), is still controversial. c-kit mutations are reportedly rare in ChCC, but there is little information in other renal neoplasms, and no reported data on mutations of platelet-derived growth factor receptor (PDGFR). In order to address these issues the authors examined five ChCC, five oncocytomas, seven papillary cell carcinomas, two collecting duct carcinomas, 12 angiomyolipomas, and three CMN, as well as 10 normal renal tissues. In the normal kidney KIT was specifically expressed in the distal nephrons. Nine of 12 (75%) angiomyolipomas contained scattered KIT-positive cells, whereas all three CMN were completely negative for KIT. The presence of KIT-positive cells in angiomyolipomas was likely to correspond to that of melanocytic marker-positive cells, which mainly showed epithelioid morphology. Polymerase chain reaction-single-strand conformation polymorphism showed no evidence of mutations of c-kit or PDGFR in any of the tumors examined.