Compared to HER2-negative (IHC 0) tumours, HER2-low tumours were significantly larger (mean size: 2.8 cm versus 2.5 cm; P = 0.013) and more frequently expressed both HR (ER: 89.3% versus 81.0%; P = 0.015; and PR: 76.7% versus 66.7%; P = 0.025). The gene discussed is ERBB2; the disease is neoplasm.