Breast cancer is a disease in which malignant (cancer) cells form in the tissues of the breast.

The most common type of breast cancer is ductal carcinoma, which begins in the cells of the ducts. Cancer that begins in the lobes or lobules is called lobular carcinoma and is more often found in both breasts than are other types of breast cancer. Inflammatory breast cancer is an uncommon type of breast cancer in which the breast is warm, red, and swollen.

Age and health history can affect the risk of developing breast cancer.

Anything that increases your chance of getting a disease is called a risk factor. Risk factors for breast cancer include the following:

• Older age
• Menstruating at an early age
• Older age at first birth or never having given birth
• A personal history of breast cancer or benign (noncancer) breast disease
• A mother or sister with breast cancer
• Treatment with radiation therapy to the breast/chest
• Breast tissue that is dense on a mammogram
• Taking hormones such as estrogen and progesterone
• Drinking alcoholic beverages
• Being white

Breast cancer is sometimes caused by inherited gene mutations (changes).

The genes in cells carry the hereditary information that is received from a person’s parents. Hereditary breast cancer makes up approximately 5% to 10% of all breast cancer. Some altered genes related to breast cancer are more common in certain ethnic groups.

Women who have an altered gene related to breast cancer and who have had breast cancer in one breast have an increased risk of developing breast cancer in the other breast. These women also have an increased risk of developing ovarian cancer, and may have an increased risk of developing other cancers. Men who have an altered gene related to breast cancer also have an increased risk of developing this disease.

Breast Cancer Treatment at Moores UCSD Cancer Center