ESR1 was among the 54 genes whose high baseline expression correlated with low residual proliferation in HER2+ tumours (r = − 0.62, p = 2.19E−03) while there were no such significant relationships with ESR1 in the HER2− group (Additional file 5: Figure S3d; Additional file 2: Table S17). Here, ERBB2 is linked to neoplasm.