ERBB2 and neoplasm: HR−/HER2− and HER+ tumours were relatively more frequent among women under age 45 years (HR−/HER2−: 23.6%, HER2+: 20.5%) compared to those within the screening age range (HR−/HER2−: 13.4%, HER2+: 13.9%) and the older age group (HR−/HER2−: 10.4%, HER2+: 11.5%).