TP53 and breast neoplasm: Despite being numerically higher in HER2-zero subgroup, TP53 mutation rate was not statistically different between HER2-zero and HER2-low breast tumors regardless of HR status (HR-positive [HER2-zero vs. HER2-low], 33.3% vs. 26.2%, p = 0.325; HR-negative 86.7% vs. 72.4%, p = 0.209; Additional file 1: Fig. S6A).