SRC (proto-oncogene tyrosine-protein kinase Src) is a member of multiple signaling pathways and activation and/or overexpression has been observed in many cancers. Simple variants in SRC are seen in about 0.3% of all tumors, including 3% of skin tumors and 2-3% of gastrointestinal tumors. SRC activiation may predict response to SRC inhibitors currently in clinical development.