The HLBCs included in the present study were composed of both ER-positive and ER-negative tumors, which were carefully characterized at the ERBB2 gene level by FISH to provide a precise categorization of the heterogeneity of HLBCs that is already seen in clinical practice but never considered in translational studies (score 2+ carcinomas with normal HER2 gene CN – HLBC-2N – or with HER2 gene CN in the equivocal range – HLBC-2E). This evidence concerns the gene ESR1 and carcinoma.