A galactocele (also: lacteal cyst or milk cyst) is a retention cyst containing milk or a milky substance that is usually located in the mammary glands. It is caused by a protein plug that blocks off the outlet. It is seen in lactating women on cessation of lactation. Once lactation has ended the cyst should resolve on its own without intervention. A galactocele does not cause infection as the milk within is sterile and has no outlet for which to become contaminated. Attempts to drain the cyst are unsuccessful because the protein plug remains intact and milk production continues. It presents as a large, soft, fluctuating lump in the lower part of breast. It is not usually painful. Treatment is by aspiration of the contents or by excision of the cyst. Antibiotics are given to prevent infection.
Galactocele may be associated with oral contraceptive use.