ESR1 and breast cancer: TP53-mut cases were frequently negative for ER and/or PR (79%, p < 0.0001 and 57%, p = 0.006, respectively); consequently, the TP53 gene alterations were predominant in the TN BC subtype (81%) and were relatively rare in HER2+ (26%), LB (39%), and LA (9%) BC subtypes (all p < 0.05; Figure 3A).