In the present work, we have shown that: 1) the development of mammary epithelium appears normal in galectin-7-deficient mice; 2) absence of galectin-7 delayed the development of MMTV-ErbB2 mammary tumors, and 3) expression of gal-7 correlates with a higher frequency of mammary tumors with Her-2-positive tumors. Here, LGALS7 is linked to breast cancer.