A very low percentage of C-KIT negative gastrointestinal stromal tumors (GIST) contain PDGFRA mutations, benefiting from imatinib in a way comparable to CML patients do, although C-KIT positive GIST also respond not only to imatinib but also sunitinib, eventually developing resistance. This evidence concerns the gene KIT and chronic myelogenous leukemia, BCR-ABL1 positive.