Mammary fibromatosis. A benign spindle-cell tumor with significant risk for local recurrence.

Twenty-two patients with fibromatosis of the breast were studied to define the clinical and pathologic features of this uncommon stromal tumor. All were female patients, 14 to 80 years (median, 25). Bilateral lesions were synchronous in three and asynchronous in one case. One tumor grew near a saline breast implant, one followed trauma, and one arose at the site of excision of a fibroadenoma a year earlier. No patient had Gardner's syndrome. Two patients had contralateral carcinoma and one was previously treated for non-Hodgkin's lymphoma. Two lesions were subareolar. Size ranged from 1 to 10 cm (average, 3 cm). Microscopically, some of the fibrocollagenous proliferations were keloidal. Others were more cellular with rare mitoses (less than 1/10 high-power field). Focal lymphoid infiltrates in about 50% of cases were mainly peripheral. Twenty were treated first by excision and two had mastectomy with residual tumor found in one breast. Six patients (27%) had recurrences after 2 to 72 months (average, 30 mo) including one bilateral recurrence. Recurrences in four cases were treated by reexcision, one had no treatment, and one mastectomy was performed for a 4-cm recurrence. Although histologically benign, mammary fibromatosis recurs locally and rarely when recurrent requires radical surgery. It should not be mistaken for an inflammatory condition. Wide local excision is recommended for initial therapy.