PDGFRB and gastrointestinal stromal tumor: For example, a tyrosine kinase inhibitor, imatinib mesylate, was originally developed for the treatment of chronic myelocytic leukemia, which has a unique chromosome translocation; later, imatinib mesylate was repurposed to gastrointestinal stromal tumor (GIST), which is characterized by mutations or overexpression of c-kit and PDGFR [14,15,16,17,18].