Worldwide, breast cancer is the most common cancer in women. It can also occur in men, but it is very rare. The causes of the cancer are not fully understood, but various risk factors have been identified.
The principal one is age: the risk of developing it increases with age, and most cases occur in women over 50. Other risk factors include: a family history of the disease; having started periods at an early age or having a late menopause; not having had children or having them late in life; being overweight; moderate to heavy alcohol intake; using the combined oral contraceptive pill; and hormone replacement therapy. In some cases, breast cancer may be linked to inherited genes, including the genes known as BRCA1 and BRCA2.
The first noticeable symptom of breast cancer is often a painless lump. Other symptoms include a change in breast size or shape; a lump or swelling in the armpit; dimpling of the skin over the breast lump; a rash around the nipple; a change in the appearance of the nipple, such as becoming inverted (retracted inward); and an unusual nipple discharge, which may contain blood.
The cancer may spread to other parts of the body, such as the lungs. Possible treatments include surgery, chemotherapy, and radiation therapy. In some cases, hormone therapy or biological therapy medication may also be used. Mammography screening to detect breast cancer early is available in some countries.