MECs can be detected by specific markers (p63, CD10, α-smooth muscle actin) and constitute a major criterion for pathologists to distinguish between ductal carcinoma in situ (DCIS), for which epithelial cells are separated from the stroma by this continuous layer of MECs, and invasive ductal cancer (IDC), for which cancer cells are in direct contact with stroma cells (Allinen et al., 2004; Polyak and Hu, 2005). The gene discussed is TP63; the disease is ductal breast carcinoma in situ.