Fibromatosis of the breast.

Two cases of fibromatosis of the female mammary gland treated by local excision and with a follow-up of 11 and 3 years, respectively, are described. Fibromatosis confined to the breast and not involving the underlying fibroaponeurotic fascia is a rare lesion. Among the handful of cases reported in the literature, diagnostic errors are known to have led to unnecessary mastectomy. In the breast, fibromatosis behaves in the same fashion as in the soft tissues: an aggressive infiltrative lesion with a proclivity for local recurrence following inadequate excision but without potential for distant metastasis. Clinically, it may simulate carcinoma; when suspected histologically during frozen section study, surgical resection should be limited to wide local excision and a definitive plan of therapy deferred until the lesion can be examined carefully with permanent sections.