KIT and gastrointestinal stromal tumor: Because NTRK fusion genes are mutually exclusive with other driver mutations, if mutually exclusive genetic alterations [e.g., epidermal growth factor receptor (EGFR) gene mutations, anaplastic lymphoma kinase (ALK) fusion genes, and ROS1 fusion genes in non-small cell lung cancers; rapidly accelerated fibrosarcoma (RAF) gene mutations in malignant melanoma and colorectal cancer; and KIT gene mutations in GIST] of mitogenic pathways (groups of genes encoding the growth factor receptor, RAS, and MAPK pathways) are detected [48], a search for NTRK fusion genes is not necessary.