SDHB and renal cell carcinoma: In the second study immunohistochemistry was used to identify 36 SDHB-deficient RCCs from 27 patients.5 All 36 were positive for SDHA expression and germline SDHA, B, C, and D mutation testing of 17 patients found 16 SDHB mutations, 1 SDHC mutation and no mutations in either SDHA or D. This study also included a summary of 53 previously reported RCC patients exhibiting an SDH mutation.