HER-2/neu overexpression has been observed by various diagnostic modalities in 20–30% of human breast cancers and is associated with a poorer overall survival and resistance to hormone based therapy (Slamon et al, 1987, 1989; Berchuck et al, 1990; Liu et al, 1992; Press et al, 1994; Pauletti et al, 1996; Allred and Swanson, 2000; Jacobs et al, 2000). This evidence concerns the gene ERBB2 and breast cancer.