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Renal cell carcinoma (RCC) is a heterogeneous term comprising a group of neoplasms of renal origin. There are 4 major histologic subtypes of RCC: conventional (clear cell RCC, 75%), papillary (15%), chromophobic (5%), and collecting duct (2%). Multiple genes are involved in the molecular pathogenesis of RCC. VHL is a tumor suppressor gene responsible for hereditary (von Hippel-Lindau) and sporadic variants of conventional (clear cell) RCC. In the absence of VHL, hypoxia-inducible factor alpha (HIF-alpha) accumulates, leading to production of several growth factors, including vascular endothelial growth factor and platelet-derived growth factor. An oncogene, MET has been found to be mutant in cases of hereditary papillary renal cancer (HPRC), although the incidence of c-MET mutations is low in sporadic papillary RCC. Once activated, MET mediates a number of biological effects including motility, invasion of extracellular matrix, cellular transformation, prevention of apoptosis and metastasis formation. Mutations in the fumarate hydratase (FH) gene cause hereditary leiomyomatosis and renal cancer syndrome (HLRCC) papillary renal tumors, although the incidence of FH mutations in sporadic tumors is unknown. Loss of functional FH leads to accumulation of fumarate in the cell, triggering inhibition of HPH and preventing targeted pVHL-mediated degradation of HIF-alpha. BHD mutations cause the Birt-Hogg-Dube syndrome and its associated chromophobe, hybrid oncocytic, and conventional (clear cell) RCC. The incidence of BHD mutations in sporadic renal tumors is not known.
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