What is Breast Cancer?


Breast cancer is the most common cancer occurring in women (excluding cancers of the skin) and the second most common cause of death from cancer in women after lung cancer. Men can also develop breast cancer, but male breast cancer is rare, accounting for less than 1% of all breast cancer cases. If diagnosed at an early stage, breast cancer has an encouraging cure rate: up to 97% of women diagnosed with localized breast cancer will survive five years after their diagnosis. Even if the cancer is found at a more advanced stage, new therapies have enabled many people with breast cancer to experience a good quality of life.

The breast is comprised mainly of fatty tissue. Within this tissue is a network of lobes, which are made up of tiny, tube-like structures (called lobules) that contain milk glands. Tiny ducts connect the glands, lobules, and lobes and carry the milk from the lobes to the nipple, located in the middle of the areola (darker area that surrounds the nipple of the breast). Blood and lymph vessels run throughout the breast; blood nourishes the cells, and the lymph system drains bodily waste products.

The main forms of breast cancer are:

* Invasive ductal carcinoma - This type of breast cancer develops in the milk ducts and accounts for about 79 percent of cases. It can break through the duct wall and invade the breast's fatty tissue, then metastasize (spread) to other parts of the body through the bloodstream or lymphatic system.
* Invasive lobular carcinoma - This type of breast cancer accounts for about 10 percent of cases and originates in the breast's milk-producing lobules. It also can spread to the breast's fatty tissue and other places in the body.
* Medullary, mucinous and tubular carcinomas - These are three slow-growing types of breast cancer. Together they represent about 10 percent of all breast cancers.
* Paget's disease - This type represents about 1 percent of breast cancers. It starts in the milk ducts of the nipple and can spread to the areola (dark circle around the nipple). Women who get Paget's disease usually have a history of nipple crusting, scaling, itching or inflammation.
* Inflammatory carcinoma -This type accounts for about 1 percent of all cases. Of all breast cancers, inflammatory carcinoma is the most aggressive and difficult to treat, because it spreads so quickly.
* Ductal carcinoma in situ (DCIS) - DCIS occurs when cancer cells fill the ducts but haven't yet spread through the walls into fatty tissue. Nearly all women diagnosed at this early stage can be cured. Without treatment, about 25 percent of DCIS cases will lead to invasive breast cancer within 10 years.
* Lobular carcinoma in situ (LCIS) - LCIS is less common and less of a threat than DCIS. It develops in the breast's milk-producing lobules. LCIS doesn't require treatment, but it does increase a woman's risk of developing breast cancer.