ERBB2 and breast cancer: Mean absolute AR expression was also highest in BrM from HER2+ breast cancer (mean AR expression 53.1%), followed by HR+/HER2− breast cancer (36.5%), and lowest in TNBC (15%) (ANOVA p = 0.023, p = 0.019 for Tukey HSD between HER2+ vs. TNBC) (Figure 1c).