ESR1 and neoplasm: Similarly, ERBB2 mutations were found in similar proportions in ER+ (2.8%) and ER− tumours (3.2%), but there was a higher proportion of mutations at codon 755 in ER+ tumours (13 out of 53 ER+, 1 out of 22 ER−; P=0.05331, Fisher's exact test) and the gene had a higher ONC score than in the ER− cohort (ER+: ONC=40%, ER−: ONC=12%).