The incidence of breast cancer is strongly correlated to genetic factors. A woman whose mother had breast cancer has a two to three times greater chance of suffering breast cancer than the average woman. In other words, family medical histories are crucial risk factors.
乳癌的發生與遺傳基因有相當的關聯性；若母親有乳癌，女兒罹患乳癌的機率為一般人的 2 至 3 倍，家族病史無疑是乳癌的高危險因子。