SDHB and gastrointestinal stromal tumor: The association of germline loss-of-function mutations in SDHx genes and loss of SDH subunit protein expression in paraganglioma–pheochromocytoma and gastrointestinal stromal tumors are well established (Neumann et al. 2002, 2004, Doyle et al. 2012, Dwight et al. 2013).