Overexpression of c-met proto-oncogene associated with chromophilic renal cell carcinoma with papillary growth

 Various genetic changes are involved in human renal cell carcinomas (RCCs). However, the molecular events related to other cytomorphological subtypes of RCC are not well known, apart from the relationship between the von Hippel-Lindau tumour suppressor gene and clear cell subtype RCC. We examined the overexpression of several growth factor receptors immunohistochemically and analyzed their relationship to the cytomorphological characters in 120 cases of RCCs. These receptors included c-met proto-oncogene product (c-MET), epidermal growth factor receptor (EGFR) and transforming growth factor beta receptor II (TGFβR). The overexpression of c-MET was detected in all cases (20/20) of the tubulo-papillary growth type and 78.3% (18/23) of chromophilic cell subtype, resulting in a very significant associations between c-MET overexpression and tubulo-papillary growth RCCs (P<0.0001), c-MET and chromophilic subtype RCCs (P<0.0001), and c-MET and EGFR (P<0.0001). EGFR overexpression was significantly associated with the compact growth RCCs (49/89, P<0.0001), clear cell subtype RCCs (P<0.005) and the overexpression of TGFβR (P<0.0001). These results strongly suggest a close correlation between the overexpression of c-MET and development of the chromophilic subtype of RCC with papillary growth pattern. EGFR expression is closely related to the pathogenesis of the clear cell subtype of RCC with compact growth pattern. The overexpression of c-MET, EGFR, and TGFβR may have roles that are individually significant in the morphogenesis of RCC.