ESR1 and ductal breast carcinoma in situ: We analyzed the methylation status of the PRKD1 promoter in 34 cases of “normal” tissue (from mammoplasty or adjacent to tumor), 22 cases of ductal carcinoma in situ (DCIS), 22 cases of estrogen receptor-positive, HER2-negative (ER+/HER2-) invasive lobular carcinoma (ILC), 43 cases of ER+/HER2- IDC, 93 cases of HER2+ IDC and 96 cases of triple-negative IDC (Figure 2B,C).