RESUMEN
BACKGROUND: Breast fibromatosis (BF) is a rare benign pathological entity. Its etiology is unknown, but it has been associated with surgical trauma and certain genetic disorders. CLINICAL CASES: Case 1. The patient was a 17-year-old female with a 20 x 15 cm firm and fixed mass in the right breast. A core-needle biopsy was taken with a pathology report of a phyllodes tumor. Mammography revealed a well-differentiated lesion with no evidence of muscle invasion. The patient underwent wide surgical resection with thoracotomy and chest wall resection of the affected ribs. Pathology reported a 19 x 18 x 9 cm BF with a positive surgical margin. Oral colchicine was administered and at 3 months of follow-up the patient is disease free. CASE 2. The patient was a 49-year-old female with a 7 x 5 cm solid right breast mass located at the medial-upper quadrant and fixed to the pectoralis major muscle. Mammography and magnetic resonance imaging revealed a mass infiltrating thoracic muscles. Wide surgical resection was performed with immediate latissimus dorsi reconstruction. Pathology report showed a BF with muscle invasion. At 3 months postsurgery, the patient is disease free. CONCLUSIONS: BF is a rare entity with a locally aggressive behavior. The infiltrative nature of this disease is associated with a tendency to recur locally. Its clinical and imaging features can mimic breast cancer. Differential diagnosis should be made before attempting treatment. The standard therapeutic modality is wide surgical resection, and radiotherapy is reserved for some cases with positive surgical margins.