HER2 is overexpressed in 25–30% of all breast cancers (Cobleigh et al, 1999; Andersson et al, 2002) and probably in a higher percentage in the more malignant subgroup that form lymph node or distant metastases (Xu et al, 2002; Eccles, 2002; Esteva et al, 2002, see also the results in this study). Here, ERBB2 is linked to breast carcinoma.