An observational study evaluated the clinical and molecular features of KIT/PDGFRA WT-GISTs in a cohort (patients < 19 y with GIST or > 19 y with WT-GIST), which was characterized by IHC for SDHB, sequencing of SDH genes, determination of SDHC promoter methylation, as well as germline testing of SDH genes for some of them (consented). Here, SDHB is linked to gastrointestinal stromal tumor.