PDGFRB and gastrointestinal stromal tumor: This study is the first report of somatic inactivation of the NF1 gene in a sporadic SDH-intact GIST lacking gain of function mutations in KIT, PDGFR, and BRAF. Although tissue from the primary tumor from this patient was not available for analysis, it is reasonable to suggest that somatic inactivation of NF1 may have been an early causative event in this case.