Under pathological conditions, excessive c-kit signaling is often associated with tumor formation and progression in gastrointestinal stromal tumors (GISTs), melanoma, small cell lung carcinoma, testicular carcinoma, etc. Imatinib, a relatively selective tyrosine inhibitor, is a target particularly of BCR-ABL, platelet-derived growth factor receptor (PDGFR), and c-kit. This evidence concerns the gene KIT and small cell lung carcinoma.