The molecular classification of breast cancer was introduced 20 years ago and since then several new subtypes have been included, such as claudin-low (characterized by the low expression of E-cadherin, high expression of epithelial-to-mesenchymal transition (EMT) genes, and expression of stem cell-like genetic signatures) [3] or molecular apocrine breast cancer (an aggressive form of ER-negative breast cancer which expresses androgen receptor and has a poor clinical prognosis) [4]. The gene discussed is CDH1; the disease is breast carcinoma.