SDHB and cancer: SDH is a mitochondrial enzyme complex and located in the inner membrane of the mitochondria,104it comprised of four subunits: SDHA, SDHB, SDHC, SDHD.9Genetic alterations in any of these four genes or SDHAF2 lead to SDH complex dysfunction and loss of SDHB expression.105SDH Mutations have been demonstrated to be implicated in the tumorigenesis of different types of cancers including GISTs.104, 106Almost 50% of KIT and PDGFRA WT-GISTs are marked by alterations involving the SDH complex40and fall into SDH-competent or SDH-deficient.