There were nine diagnoses of GIST in this study after second opinion (1.5%), and diagnostic discrepancy was noted in four; in these, the diagnosis was changed from mesothelioma (on morphology), SFT (DOG1 positive but no KIT or PDGFRA mutations on second-opinion workup), “vascular lesion” (DOG1 negative, PDGFRA mutation positive), and leiomyoma (KIT mutation positive). The gene discussed is KIT; the disease is leiomyoma.