ESR1 and ductal breast carcinoma in situ: Fig. 2d and g shows the expression of Slug and ERα analyzed by immunohistochemistry (IHC) in breast tissues from breast cancer patients with known clinical diagnosis and follow-up. Each sample/spot on the tissue microarray (TMA) platform represented different cancer subtype and stage. Our data show low Slug expression in normal and ductal carcinoma in situ (DCIS) breast cancer samples, while Slug expression was significantly increased in infiltrating ductal carcinoma (IDC) (Fig. 2d and e). An inverse correlation is shown between Slug and ERα expression in Fig. 2f and g.