On this basis, four major surrogate intrinsic subtypes are commonly and widely recognized (Figure 1): (i) luminal A-like (ER+, PR+, HER2−, Ki67low); (ii) luminal B-like (ER+ and/or PR+, HER2+/−, Ki67low/high); (iii) HER2-enriched (ER−, PR−, HER2+, Ki67high); and (iv) triple-negative breast cancer (TNBC; ER−, PR−, HER2−, Ki67high), further subclassified into basal-like, claudin-low, mesenchymal, luminal androgen receptor, and immunomodulatory subgroups [8,9]. This evidence concerns the gene ESR1 and triple-negative breast carcinoma.