ESR1 and ductal breast carcinoma in situ: Comedo-DCIS accounts for ~10% of all DCIS and differs from other DCIS subtypes in being ER−, PgR−, Her2/neu+ and having the highest risk for progression and post-operative recurrence [17,18] Comedo-DCIS tumors are easily distinguished from other DCIS by the characteristic central comedo necrosis [19].