Breast cancer is a malignant tumor that usually forms in the milk ducts, or in the milk-producing glands of the breast. It is almost exclusively found in women, but men can get breast cancer, too. Breast cancer is the second leading cause of death from cancer among women, resulting in over 40,000 deaths in 2009, according to the National Cancer Institute.
Ductal Carcinoma in Situ
With this type, the cancer cells are in the lining of the milk ducts and have not spread to any surrounding tissue.
Invasive Ductal Carcinoma
Invasive means that the cancer cells have spread to the surrounding tissue and possibly to other parts of the body. The National Breast Cancer Foundation says invasive ductal carcinoma accounts for about 78 percent of all breast cancers.
Invasive Lobular Carcinoma
Making up about 5 percent of all breast cancers, this type forms in the lobules of the breast. Lobules are the glands that produce milk. Invasive lobular carcinoma is cancer that spreads from the lobules to surrounding tissue. It can spread to other areas of the body, as well.
Medullary Carcinoma
Medullary carcinoma accounts for 3 to 5 percent of breast cancer types, says the American Cancer Society. It is defined by large cancer cells, whose tumor border is surrounded by immune system cells.
Mucinous Carcinoma
This type of cancer, also known as colloid carcinoma, has tumor cells that produce mucus. It is rare, making up 1 to 2 percent of breast cancer cases.
Inflammatory Breast Cancer
This aggressive and rare type of breast cancer causes the skin of the breast to become red and warm. The breast is swollen and may have a thickened, pitted appearance called peau d'orange.
Paget's Disease of the Nipple
Paget's disease of the nipple is a rare form of cancer that begins in the ducts of the breast. It first appears as a scaly, red area on the areola of the nipple that may ooze or bleed.
Metaplastic Carcinoma
This rare form of cancer is a type of invasive ductal carcinoma but has the presence of cells that come from other parts of the body, such as bone or skin cells.
Tubular Carcinoma
This is another kind of invasive ductal cancer that has a distinctive tubular configuration when viewed under a microscope. Tubular carcinomas make up only about 2 percent of all breast cancers.
