S100 calcium binding protein A4 (S100A4) is involved in a variety of physiological functions, such as cell motility, adhesion, proliferation, and metastasis.11, 12, 13, 14, 15 Mammary tumors from S100A4 transgenic mice displayed higher vessel density compared with non‐transgenic animals.16 Vessel density and S100A4 expression correlated positively in primary tumors from patients with breast cancer.17 S100A4 is a well established marker and mediator of metastatic disease.18, 19 However, the upstream molecular signaling pathway involved in S100A4‐mediated metastasis is less well defined. This evidence concerns the gene S100A4 and breast cancer.