Mammary-duct fistula is a communication between a subareolar duct and skin, usually occurring in the periareolar region. It often occurs spontaneously following underlying periductal mastitis but can also occur following incision and drainage of a nonlactating breast abscess. It occurs predominantly in younger women; the majority are smokers.

Clinical Features
Presence of a fistula in the periareolar region with associated inflammation on a background history of recurrent periductal inflammation is often noted. Patients classically report a long duration of symptoms of recurrent inflammation treated with antibiotics.

Radiology
On ultrasound, the fistulous track may be seen as a linear hypoechoic structure extending from the skin. The main objective of mammography and ultrasound is to exclude underlying abscess or malignancy.

Pathology
Macroscopic Appearance
A thickened fistulous track may be apparent in the specimen.

Microscopic Appearance
Classically, a fistulous track is seen. It is lined with granular tissue that extends from the areolar skin to an underlying duct. Extensive squamous metaplasia is commonly present in the affected duct.

Management
In the presence of acute inflammation, appropriate antibiotic therapy is necessary initially. Surgery is the only means of successfully curing this condition and will involve complete duct excision with excision of mammary-duct fistula. The wound may be left open and allowed to heal by secondary intention. Where the disease is relatively quiescent, it is reasonable to achieve healing by primary skin closure and antibiotic cover.

A.D. Purushotham, P. Britton and L. Bobrow
A prospective study of benign breast disease and the risk of breast cancer. JAMA 2002

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