Histological classification of DCIS and LCIS can be further evaluated by grading the expression levels of progesterone receptor (PR), estrogen receptor (ER), epidermal growth factor receptor 2 (ErbB2/HER2) (8), epidermal growth factor receptor (EGFR) and p53 (9–11). Here, ESR1 is linked to lobular breast carcinoma in situ.