Breast cancer occurs when cells in breast tissue grow out of control, becoming malignant. The breast consists of about 15 to 20 sections called lobes, which have multiple smaller sections called lobules. These lobules end in tiny bulbs where milk is produced. The bulbs, lobules and lobes are connected by tiny tubes or ducts, which lead to the nipple. Fibrous tissue and fat surround the lobes and all of this breast tissue rests on the muscle of the chest wall. The cells that line the ducts and lobules are those that become malignant.
Initially, these malignant cells remain inside the duct or lobule and at this early stage are called carcinoma in situ. In most cases, the cells have invaded through the wall of the duct or lobule, becoming invasive ductal cancer or invasive lobular cancer. These cells may also invade into the breast’s blood vessels or lymph vessels and spread to the lymph nodes, primarily in the armpit, or to other organs of the body.
Breast cancer may cause these symptoms:
Important facts to know
Risk factors for male breast cancer
The breast cancers that are found in men are: