FGFR2 (fibroblast growth factor receptor 2 gene) encodes the fibroblast growth factor receptor 2 protein, a receptor tyrosine kinase. The protein encoded by this gene is a member of the fibroblast growth factor receptor family, where amino acid sequence is highly conserved between members and throughout evolution. FGFR family members differ from one another in their ligand affinities and tissue distribution. A full-length representative protein consists of an extracellular region, composed of three immunoglobulin-like domains, a single hydrophobic membrane-spanning segment and a cytoplasmic tyrosine kinase domain. The extracellular portion of the protein interacts with fibroblast growth factors, setting in motion a cascade of downstream signals, ultimately influencing mitogenesis and differentiation. This particular family member is a high-affinity receptor for acidic, basic and/or keratinocyte growth factor, depending on the isoform. FGFR2 and other FGFR TKs play crucial roles in development and have been shown in cancers to be deregulated by amplification, point mutation, or translocation. Amplification or activation of FGFR2 has been reported in breast cancer and gastric cancer. FGFR2 mutations have been observed in endometrial cancer and breast cancer.