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By Mayo Clinic staffMammary duct ectasia occurs when a milk duct beneath your nipple becomes blocked or clogged. Though it's normal to worry about changes in your breasts, mammary duct ectasia is not a sign of or a risk factor for breast cancer.
Mammary duct ectasia occurs most often in women in their 40s and 50s, affecting as many as one in four women during or after menopause. It often causes no symptoms, but some women may have nipple discharge and tenderness or inflammation near the nipple (periductal mastitis).
Mammary duct ectasia usually improves without treatment. However, if symptoms persist, you may need antibiotics or possibly surgery to remove the affected milk duct.