Breast cysts are fluid-filled sacs that develop in the breast.
Breast cysts are common. In some women, many cysts develop frequently, sometimes with other fibrocystic changes (see Fibrocystic Changes). The cause of breast cysts is unknown, although injury may be involved. Breast cysts can be tiny or several inches in diameter.
Cysts sometimes cause breast pain. To relieve the pain, a doctor may drain fluid from the cyst with a thin needle (called aspiration). The fluid is examined under a microscope to check for cancer only if the fluid is bloody or cloudy, if little fluid is obtained, or if the lump is still present after the fluid is drained. Otherwise, the woman is checked again in 4 to 8 weeks. If the cyst can no longer be felt at this time, it is considered noncancerous. If it has reappeared, it is drained again, and the fluid is examined under a microscope. If the cyst reappears a third time or if it is still present after it was drained, a biopsy is done.
Rarely, when cancer is suspected, cysts are removed.
Last full review/revision March 2014 by Mary Ann Kosir, MD