Fibromatosis is an uncommon, relatively benign though locally infiltrating neoplasm consisting of well-differentiated fibroblasts surrounded by collagen bundles. The majority of the literature suggests that prevention of local recurrence mandates wide (en bloc) excision. Few more than a dozen cases of primary breast fibromatosis have been reported. Herein the clinical characteristics, diagnostic evaluation, and therapeutic options are presented. Management should be based upon principles utilized for extra-mammary primary disease-en bloc resection. This may require total mastectomy and removal of pectoralis major muscle. Breast reconstruction should be deferred for a minimum of 3 years, during which time the majority of recurrences will have become manifest.