Breast cysts usually happen due to the normal hormonal fluctuations that take place in a woman's body during her menstrual cycle. That's why they're most common among women who are still of child-bearing age. Only a small proportion of breast cysts occurs in post-menopausal women.
Breast cysts are fluid-filled sacs inside the breast. They are usually noncancerous (benign). You may have one or multiple breast cysts. A breast cyst often feels like a grape or a water-filled balloon, but sometimes a breast cyst feels firm.
Breast cysts don't require treatment unless a cyst is large and painful or uncomfortable. In that case, draining the fluid from a breast cyst can ease symptoms.
Although breast cysts can be found in women of any age, they're more common in women before menopause, typically under age 50. Breast cysts also commonly occur in postmenopausal women who take hormone therapy.
Each of your breasts contains lobes of glandular tissue, arranged like petals of a daisy. The lobes are divided into smaller lobules that produce milk during pregnancy and breast-feeding. The supporting tissue that gives the breast its shape is made up of fatty tissue and fibrous connective tissue. Breast cysts develop as a result of fluid accumulation inside the glands in the breasts.
Breast cysts may be defined by their size:
Microcysts may be seen during imaging tests, such as mammography or ultrasound, but are too small to feel.
Macrocysts are large enough to be felt and can grow to about 1 to 2 inches (2.5 to 5 centimeters) in diameter.
Experts don't know exactly what causes breast cysts. They may develop as a result of hormonal changes from monthly menstruation.
Breast cysts may be found in one or both breasts. Signs and symptoms of a breast cyst include:
A smooth, easily movable round or oval lump that may have smooth edges — which typically, though not always, indicates it's benign
Nipple discharge that may be clear, yellow, straw colored or dark brown
Breast pain or tenderness in the area of the breast lump
An increase in breast lump size and breast tenderness just before your period
A decrease in breast lump size and resolution of other symptoms after your period
Having breast cysts doesn't increase your risk of breast cancer. But having cysts may make it harder to find new breast lumps or other changes that might need evaluation by your doctor. Your breasts may feel lumpy and painful when you're menstruating, so it's important to be familiar with how your breasts feel throughout your menstrual cycle so that you'll know if something changes.
When to see Your Healthcare Provider
Normal breast tissue often feels lumpy or nodular. But if you feel a new breast lump that doesn't go away, gets bigger or persists after one or two menstrual cycles, see your doctor right away. Also see your doctor if you have new skin changes on one or both of your breasts.