SDHD and cancer: In addition to SDH subunit mutations which occur in hereditary tumors and sporadic cancers, loss of SDH function may be the result of loss of heterozygosity [33] or reduction of SDHB or SDHD subunit expression in diverse cancers including colorectal, gastric, hepatocellular, ovarian and clear cell renal cell carcinoma (ccRCC) [34–37].