Cysts are fluid filled sacs. The National Institute of Health (NIH) says they occur most often in women ages 35 to 50, and they often enlarge and become tender and painful just before the menstrual period. They are usually found in both breasts. Some cysts are so small they cannot be felt; rarely, cysts can be several inches across. Cysts often show up clearly on an ultrasound.

Although a cyst is not cancer, it’s important for a woman who notices any lump or change to see her HCP. According to NIH, when a cyst is suspected, some doctors proceed directly with aspiration, a procedure that uses a very thin needle and a syringe. Sometimes the cyst will disappear after that. If the lump turns out to be solid, it may be possible to use the needle to biopsy or withdraw a clump of cells that can then be sent to a laboratory for further testing.