There is also strong evidence to suggest a population-dependent variation in the biology of breast cancer, such as ER status, p53 gene mutation, HER-2/neu, S-phase fraction, lymphatic infiltration, sinus histiocytosis, and certain histological patterns (Sakamoto et al, 1981; Friedel et al, 1991; Elledge et al, 1994; Merchant et al, 1999). The gene discussed is ERBB2; the disease is breast carcinoma.