NR4A1 and breast cancer: Because gene expression profiling is resource intensive and not currently feasible for routine use, BC molecular subtypes can be approximated by standard immunohistochemical features with the LA subtype representing hormone receptor-positive tumours with low proliferative activity, the LB subtype representing hormone receptor-positive tumours with high proliferative activity, the HER2 subtype representing HER2+ tumours, and the basal subtype representing triple negative (TN) disease with no expression of hormone receptors or HER2 [4].