Breast Cancer

Breast cancer is a type of cancer that starts in the breast, in one or both breasts. Cancer starts when cells begin to grow out of control. Breast cancer occurs almost entirely in women, but men can get it too. Most breast lumps are benign (not cancer) — abnormal growths that do not spread outside the breast and are not life-threatening — but some benign lumps can increase a woman’s risk. Any breast lump or change needs to be checked by a health-care professional.

Breast cancers can start from different parts of the breast — most often the ducts (small canals that carry milk to the nipple) or the lobules (the glands that make milk). Less commonly they begin in the nipple, the connective tissue (stroma), or in blood and lymph vessels.

There are many types of breast cancer, determined by the kind of cells affected. Most are carcinomas — commonly ductal carcinoma in situ (DCIS) and invasive carcinoma. After a biopsy, cells are tested for estrogen and progesterone receptors and the HER2 gene/protein, and graded in the lab; these results help decide the stage and treatment options.

There is no sure way to prevent breast cancer, but there are things you can do that might lower your risk — especially helpful for women with a strong family history or certain inherited gene changes. Early detection remains the best protection.