SDHB and gastrointestinal stromal tumor: More recently, MGMT was found to be preferentially methylated in a small subset of SDH-deficient (dSDH) wild-type GIST compared with a larger subset of SDH preserved (pSDH) wild type GIST (6/9 (67%) dSDH GIST, vs 6/39 (15%) pSDH-preserved GISTs.14 Lou et al observed a significantly higher percentage of MGMT promoter hypermethylation in SDH deficient and epithelioid/mixed non-TK mutant GIST (4/7 and 8/44, respectively).15