KIT and gastrointestinal stromal tumor: Third, we may not be familiar with the tumor spectrum of imatinib treatment, and pathologists have a deep understanding that imatinib is a molecular target drug for GIST, but the most fundamental principle of imatinib is that it is a drug for the tyrosine kinase activity of BCR-ABL1, KIT, PDGFRA, etc. It was first used for chronic myeloid leukemia, was later found to be used for GIST, and can also be used for DFSP.