Indeed, ER+ tumours were scattered in subgroups 1 to 4 that are characterised by the over-expression of a cluster of genes, which includes CCND1, KRT19, IGF1R, LIV1, ESR1, GATA3, TFF1/pS2, ERBB4, PR and IGFBP4. Here, ERBB4 is linked to neoplasm.