Mammary duct ectasia

Illustration of clogged milk duct in mammary duct ectasia

Mammary duct ectasia occurs when a milk duct beneath the nipple becomes wider (dilated) and filled with fluid. The milk duct can then become blocked or clogged with a thick, sticky substance. Mammary duct ectasia usually causes no signs or symptoms, but some women may have nipple discharge, breast tenderness or inflammation of the clogged duct.