Most S100 genes, including those forming the S100A group (S100A1–14, S100A7A, and S100A16), are located in human chromosome 1q21, a region frequently associated with recombination events in tumor tissues, resulting in the uncontrolled expression of S100 members, such as the upregulation of S100A11 and S100A14 reported in breast cancer [7]. This evidence concerns the gene S100A1 and breast cancer.