Your breasts are made up of connective tissues that include a system of milk ducts — tiny passages that carry milk to the nipples. Mammary duct ectasia occurs when a milk duct beneath the nipple becomes wider (dilated), blocked or clogged with a sticky substance and inflamed.

Experts don't know exactly what causes mammary duct ectasia. Some speculate the cause to be associated with:

  • Breast tissue changes due to aging. As you age, the composition of your breast tissue changes from mostly glandular to mostly fatty in a process called involution. These normal breast changes can sometimes lead to blockage of a milk duct and the inflammation associated with mammary duct ectasia.
  • Smoking. Cigarette smoking may be associated with widening of milk ducts, which can lead to inflammation and, possibly, mammary duct ectasia.
  • Nipple inversion. A newly inverted nipple may obstruct milk ducts, causing inflammation and infection. A nipple that's newly inverted also could be a sign of a more serious underlying condition, such as cancer.
Jun. 02, 2012