ERBB2 and breast cancer: Gene amplification and overexpression of ERBB2 has been reported in several types of cancer, including the breast cancer, and has been shown to contribute to a poor clinical outcome (Slamon et al, 1989; Gullick et al, 1991; Seshadri et al, 1993; Berns et al, 1995; Liu et al, 2007; Van Agthoven et al, 2009a).