One in 8-9 women in the United States will be diagnosed with breast cancer sometime during her lifetime. Breast cancer can occur in families, but most cancers occur in women with no family history of breast cancer.
Normal Breast Anatomy
Breast cancer starts in the ductal system that normally produces the milk when a woman is breast feeding her baby. The two main types are lobular (where the milk is made) and ductal (the tiny tubes that carry the milk from the lobules to the nipple).
Breast cancer goes through a progression from abnormal cells that are contained within the ducts and lobules (ductal carcinoma in-situ) to malignant cells that invade outside of them (invasive ductal or lobular cancer). Carcinoma in-situ is not life threatening and the goal is to prevent them from becoming invasive. The progression of breast cancer cells is shown in the diagram.