A, Percent positive expression in GIST subtypes including KIT-mutant (n=65), PDGFRA-mutant (n=10), and SDH-deficient (n=12) tumors for the proteins DOG1, KIT, PDGFRA, SDHB, HAND1, HOXC10, PLAGL1 and BARX1. B, IHC of KIT-mutant GIST stratified by anatomic location and localized or metastatic disease. C, IHC of KIT-mutant GIST stratified by mutational subtype. All exon 13 and compound mutation tumors were derived from metastatic disease. D, IHC of GIST with exemplary positive and negative expression of HAND1 and BARX1; scale bar indicates 20 μm. E, Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of select proteins for mutational subtype.