KIT and gastrointestinal stromal tumor: In vitro GIST cell lines, different KIT mutations were detected, such as classical GIST-T1 (primary mutation in KIT exon 11—Δ560–578) and GIST-882 (primary mutation in KIT exon 13—K642E) cell models, the biological effects upon imatinib treatment can be significantly different [38–40].