Among the peptide growth factor receptors frequently implicated in endometrial cancer are members of the type I receptor tyrosine kinase family, which includes HER1 (epidermal growth factor receptor (EGFR)), HER2, HER3, and HER4 (Srinivasan et al, 1999; Santin et al, 2002). The gene discussed is ERBB3; the disease is endometrial cancer.