- During a 15 year period, 18 patients with 28 mamillary fistulas were treated. In eight women, periareolar abscess had preceded recognition of a fistula. Ten patients were primarily diagnosed as having mamillary fistula. In six patients, when the underlying fistula tract was not identified and excised at the time of operation, discharging sinus reoccurred. Twenty-two fistulas were completely excised together with an extensive lactiferous duct system. Operative wound was primarily closed using antibiotic cover. Periareolar abscess and mamillary fistula should be treated primarily by complete excision of the fistula tract and extensive duct system of the breast.