Desmoid-type fibromatosis of the breast: A report of 2 cases.

Mammary fibromatosis is a rare and locally aggressive benign tumor of the breast; it originates from fibroblasts and myofibroblasts within the breast parenchyma and does not metastasize. The condition is locally aggressive and has a high rate of recurrence. The etiology of mammary fibromatosis is unknown. Breast imaging examinations are not specific for fibromatosis and often imitate breast cancer. The current study presents 2 cases of women with breast fibromatosis, the first of which exhibited a locally advanced aggressive form of the disease, where breast surgery and en bloc resection of the underlying regions of the thoracic wall were required. In the second case, breast imaging examinations suggested an invasive breast tumor, probably carcinoma, infiltrating the muscles of the chest wall. An ultrasound-guided core needle biopsy revealed a low-grade myofibroblastic proliferation consistent with breast fibromatosis. The patient underwent a right quadrantectomy, with a partial resection of the underlying musculature. The patients remain disease-free at the time of writing. As involvement of the breast in patients with desmoid-like fibromatosis as rare, the present study reports 2 cases with clinical features and histological findings in order to improve and add to the knowledge of this disease.