SDHB and gastrointestinal stromal tumor: Furthermore, in a 2016 study, a large sample set of 95 patients was investigated, in which 84 had succinate dehydrogenase-deficient GIST caused either by SDH mutations (75%) or by SDHC promoter hypermethylation (25%), and 18 were syndromic GISTs with chondromas and/or paragangliomas.