Luminal B breast cancer has been reported to have lower expression of hormone receptors, higher expression of proliferation markers, and higher histologic grade than Luminal A. It also exhibits worse prognosis and has a distinct profile of response to hormone therapy and chemotherapy.41 So far, the molecular definition of Luminal B disease has also been of limited use in tailoring breast cancer treatment. This evidence concerns the gene NR4A1 and breast cancer.