A mammary duct (mammillary) fistula involves a communication between a lactiferous duct in female breast and the skin surface. It may pose a problem during periods of lactation, stress, or menstruation.


Risk factors for development of mammary duct fistula:

(1) periareolar abscess

(2) periductal mastitis with mammary duct ectasia

(3) previous breast surgery (typically a breast biopsy)

(4) spontaneous cutaneous or surgical drainage of an abscess

(5) congenital or acquired duct obstruction

(It would be interesting to note if infection with Staphylococcus aureus is a risk factor.)


Berna et al reported that some cases may not involve a cutaneous fistulas communicating with the lactiferous ducts but rather arise from follicular-sebaceous cysts that become infected.


The fistula tract and originating duct can be surgically excised with primary closure or left open to granulate. However, some patients may have a recurrence, especially if there is active infection. Appropriate antibiotic therapy after surgery may reduce the risk of recurrence.


Berna et al used a combination of microwave and ultrasound therapy to the fistula site for 3 weeks which resulted in resolution without requirement for surgery and low risk of recurrence. A second course of therapy with or without steroid injection was successful in resolving recurrences.


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