Eighty percent of all breast lumps are benign—a comforting thought for most women. Your breast tissue is constantly changing throughout your life, which means you should be prepared for differences and changes at every stage of your life. Some of the causes for breast abnormalities, beside breast cancer, include:

Mastitis is a breast infection that is characterized by tenderness, redness and inflammation of the breast and can also cause flu-like symptoms. Mastitis most commonly occurs in women who are breastfeeding.

Fibrocystic breast disease is also known as generalized breast lumpiness and tenderness, experienced by women during menstruation. These lumps are actually milk ducts, but they develop small cysts in response to hormones like estrogen and progesterone that are released prior to menstruation. These cysts are the most common cause of benign breast lumps in women.

Fibroadenomas are benign tumors found in the breast that are made up of an excess of lobules, the glands that produce milk. These tumors are solid, round and rubbery feeling lumps and most often are found in women from 20 to 30 years old.

Simple cysts. These are fluid-filled sacs in both breasts that may change with your menstrual cycle.

Intraductal papillomas are small growths near the nipple that can produce bleeding from the nipple and usually occur in women from 30 to 45 years old.

Nipple discharge is sometimes normal. If you have a history of breastfeeding, you may experience nipple discharge. If you’re not breastfeeding, an increase in certain hormones such as prolactin may cause a milky discharge to emit from your nipples. Stimulation or squeezing can also produce a nipple discharge. The most common causes of nipple discharge include oral contraceptives, increased breast stimulation and tricyclic antidepressants. If the discharge is spontaneous, you should see a doctor. Spontaneous discharge means the discharge was not triggered by stimulation or breastfeeding.