FGFR3 and breast cancer: FGFR3 is located on chromosome 4p16.3 and is found mutated in a very low percentage of breast cancer patients, in particular in the extracellular (R248C, S249C) or the transmembrane (G370C, S371C, Y373C, G380R, A391E) protein domains, and more rarely within the kinase domain (K650E, K650N, K650M, K650T, K650Q and N540S) [104].