ERBB2 and ductal breast carcinoma in situ: Our analysis showed, compared with DCIS, DCISM was more ER negative (33.1% vs. 17.5%; P < 0.001), PR negative (44.9% vs. 27.3%; P < 0.001), and HER2 positive (36.5% vs. 32.4%; P = 0.009).