GEP studies have consistently identified at least two groups of ER+ tumours; the less favourable LB group being characterised by higher histological grade and higher expression of proliferation and HER2-related genes, such as MKI67, MYBBL2, CCNB1, HER2 and GRB7, and lower levels of ER-related genes. Here, GRB7 is linked to neoplasm.