ESR1 and ductal breast carcinoma in situ: Based on the expression of these biomarkers, DCIS can be molecularly subtyped into luminal A (ER+, PR+, HER2/neu-, Ki-67 labeling index<14%), luminal B (ER+, PR+, HER2/neu-, Ki-67 labeling index>14%), luminal HER2/neu (ER+, PR+/-, HER2/neu+, Ki-67 labeling index-variable), HER2/neu enriched (ER-, PR-, HER2/neu+, Ki-67 variable), and triple-negative (ER-, PR-, HER2/neu-, Ki-67 labeling index-variable) [2].