ESR1 and breast carcinoma: When ER+ tumors were, in turn, sub-divided according to their HER2 status into ER+/HER2- and ER+/HER2+, the ER+/HER2+ subgroup exhibited the highest FASN protein expression compared to basal-like, HER2-enriched, and ER+/HER2-negative breast cancer groups (Figure 7).