24th May 2025

Mammary Duct Ectasia/Periductal Mastitis

Mammary duct ectasia and periductal mastitis are terms that are often used interchangeably, though some literature has described them as being two distinct entities. They are another common cause of benign nipple discharge, accounting for up to 30% of cases. Duct ectasia is typically seen in perimenopausal women over 35 years of age and is thought to arise due to age-related shortening and widening of the ducts, with subsequent obstruction secondary to inspissated secretions. Periductal mastitis, however, is more common in younger women and occurs when the ducts become inflamed and/or infected. The latter has a strong association with smoking.

Duct ectasia may be asymptomatic, but can present with thick, “cheesy” nipple discharge, but can also be watery in consistency, as well as brown, green or blood-stained. Occasionally, a lump may be felt behind the nipple and the nipple itself may become red, tender and retracted. At this point, periductal mastitis may be more appropriate terminology and the surrounding breast tissue may become painful, hot and erythematous. If left untreated, a pus filled abscess or fistula may also develop.

Mammography and ultrasound imaging reveal similar features, characterised by dilated, branching tubular structures in the subareolar region. X-ray may also show rod like calcifications pointing towards the nipple. Biopsy of the area shows dilated duct lumens containing foamy macrophages, with surrounding periductal chronic and/or granulomatous inflammation, particularly if there has been rupture. In the latter stages, periductal fibrosis and obliteration of the lumen may also be seen.

Duct ectasia will often resolve spontaneously and may only require simple analgesia for pain relief. Periductal mastitis will usually be treated with a course of antibiotics, though some cases will resolve on their own accord. In the presence of complications, such as an abscess or the development of a fistula, specialist input may be required for further management. This can include aspiration of the pus, or incision and drainage. Surgical intervention may be warranted in recurrent disease or in cases that do not respond to the aforementioned measures. However, neither duct ectasia or periductal mastitis are associated with an increased risk of developing breast cancer.