Furthermore, the authors showed that FGF5 secreted by cancer-associated fibroblasts (CAF) in the microenvironment might be responsible for the high activation of FGFR2 on the neighbouring epithelial cells [137], confirming the potential signalling switch between HER2 and FGFR2 in breast cancer (figure 4). This evidence concerns the gene FGFR2 and breast carcinoma.