ERBB2 and breast cancer: HER-2/neu is ubiquitously expressed in many epithelial tumours and known to be overexpressed in approximately 30% of all ovarian and breast cancers (Slamon et al, 1989,2001), 35–45% of all pancreatic carcinomas (Yamanaka et al, 1993) and up to 90% of colorectal carcinomas (Maxwell-Armstrong et al, 1998) and this overexpression was shown to correlate with aggressiveness of malignancy and poor prognosis (Slamon et al, 1989; Pauletti et al, 1996).