KIT and gastrointestinal stromal tumor: To our knowledge, approximately 50% of GIST patients develop imatinib resistance within 24 months, primarily due to acquired cis-mutations in the KIT and PDGFRA. Common resistance mutations include KIT V654A (exon 13), T670I (exon 14), D816V/D820G/N822K/Y823D (exon 17), and PDGFRA D842V (exon 18), which likely arise through Darwinian selection under TKI pressure (26, 27).