Amplification of the HER-2 gene with overexpression of the receptor is detected in 20–30% of breast cancers (Slamon et al, 1987, 1989) and is associated with a worse prognosis compared to those with HER-2-negative tumours (Slamon et al, 1987; Emi et al, 2002). Here, ERBB2 is linked to breast carcinoma.