We measured the expression of ErbB2 on breast cancer cell lines JIMT-1 and KPL-4 (Kurebayashi et al, 1999; Tanner et al, 2004), directly derived from patients with aggressive trastuzumab-resistant tumours, and on MDA-MB-361 cells that are sensitive to trastuzumab. This evidence concerns the gene ERBB2 and neoplasm.