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THE MERCK MANUAL MEDICAL LIBRARY: The Merck Manual of Medical Information--Home Edition
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Cysts
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Cysts

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Breast cysts are fluid-filled sacs that develop in the breast.

Breast cysts are common. In some women, many cysts develop frequently, sometimes as part of fibrocystic breast disease. However, in other women, cysts never develop. 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. The fluid is examined under a microscope to check for cancer. The color and amount are noted. If the fluid is bloody, brown, or cloudy or if the cyst does not disappear or reappears within 12 weeks after it is drained, the entire cyst is removed surgically, because cancer in the cyst wall, although rare, is possible.

Last full review/revision February 2003

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