The WT GIST associated with a germline SDHA mutation showed complete loss of both SDHA and SDHB protein (Figure 4 A,B), while the tumor with a somatic, heterozygous SDHA mutation showed significant decreased in SDHA immuno-expression, as well as complete loss of SDHB (Figure 4 C,D). The gene discussed is SDHB; the disease is gastrointestinal stromal tumor.