The proto-oncogene KIT encodes a type 3 transmembrane receptor tyrosine kinase. c-kit (CD117) is a growth factor receptor of the tyrosine kinase subclass III family, normally expressed in a variety of human tissues. Gain-of-function mutations of the c-kit gene have been identified that produce ligand-independent activation of c-kit and cell proliferation. Some of these mutations appear causative in the pathogenesis of adult mastocytosis and most gastrointestinal stromal tumors (GISTs). Activating KIT mutations occur in 80 - 90% of GISTs and several small molecule tyrosine kinase inhibitors (TKIs) targeting KIT that have been approved by the US Food and Drug Administration with the efficacy of each TKI strongly depending on the location of the activating KIT mutation. c-kit receptor and its ligand have been demonstrated in human colon cancer cell lines. Some studies have shown high frequency of c-Kit overexpression in stage II colon cancer patients (59.3%) with significant correlation between c-Kit overexpression and reduced disease free survival. However, other studies failed to demonstrate c-kit expression in a significant number of colorectal cancers suggesting that c-kit kinase activation is not a prominent pathogenetic feature of colorectal cancers. The role of c-Kit continues to be studied in colon cancers. The KIT D52N mutation likely represent an oncogenic gain of function mutation.