Benign breast diseases are very common, affecting most women at some point in their lives. The main types are:
Adenosis
This condition causes an increase in the size and number of milk-producing glands (lobules). Lumps can form, but they are usually painless. Sclerosing adenosis is a type of adenosis in which painful scar tissue develops in the lobules. Adenosis does not increase your chance of breast cancer.
Ductal and lobular breast hyperplasia
Hyperplasia is a noncancerous increase in cell growth. In the breast, it occurs in the cells that line the milk ducts and lobules. Cells can look like normal breast cells (usual) or distorted (atypical). Atypical hyperplasia can significantly increase breast cancer risk. Because hyperplasia doesn’t usually cause a lump, doctors often find hyperplasia on routine mammograms.
Fat necrosis and oil cysts
Fat necrosis is caused by an injury to fat tissue in the breast. It starts when fat cells die and form a greasy, fluid-filled cyst. Over time, the cyst hardens and forms a lump. Most lumps are painless, but the skin around them may look red, bruised, or thick. Fat necrosis does not affect your risk of breast cancer.
Fibroadenomas
These benign breast tumors are made of fibrous and glandular tissue. They usually affect women under age 35. A round, smooth lump that is firm or rubbery is usually the only symptom. Some fibroadenomas grow large, while others disappear without treatment. Fibroadenomas that have other cellular changes or are larger may increase breast cancer risk slightly.
Fibrocystic breast changes
Fibrocystic changes are lumps caused by changes in the fibrous tissue (fibrosis) and the formation of fluid-filled sacs (cysts). Symptoms include breast lumps and pain that tend to come and go over the menstrual cycle. Fibrocystic changes affect women of all ages but are most common during the childbearing years. Fibrosis and simple cysts do not increase breast cancer risk. More complex breast cysts have a higher risk of being cancer.
Intraductal papillomas
These benign tumors grow in the milk ducts and are made of several types of breast tissue. Symptoms include a painless lump and nipple discharge that is clear or bloody. Having several intraductal papillomas is linked to a slight increase in breast cancer risk.
Lobular carcinoma in situ (LCIS)
LCIS occurs when cells in the lobules grow faster but don’t invade other tissues. Because it doesn’t usually cause a lump or changes that can be seen on a mammogram, doctors often find it when performing a breast biopsy for another breast concern. LCIS significantly increases your risk of developing breast cancer.
Mammary duct ectasia
In this condition, the milk ducts widen, and the walls become thick. Fluid becomes trapped in the ducts, causing inflammation. Duct ectasia usually affects women around the age of menopause (age 50) and older but doesn’t increase breast cancer risk.
Mastitis
This benign breast condition causes inflammation, swelling, redness, and pain. It is usually the result of an infection, often in the milk ducts of women who are breastfeeding. There is no link between mastitis and breast cancer.
Phyllodes tumors
These rare and often fast-growing tumors develop in the fibrous tissues of the breast. They form firm lumps that may or may not be painful. Most phyllodes tumors are benign (benign tumors don’t affect breast cancer risk), but about 1 in 4 are cancerous.
Radial scars
These areas of breast tissue look like scars when examined under a microscope, but they are not true scars. Because they rarely cause symptoms, doctors typically find them when performing a breast biopsy for another purpose. Larger radial scars have an increased chance of containing cancer cells.
