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

Abstract

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.

Keywords: breast tumors; desmoid-type fibromatosis.

Figure 1.

Breast fibromatosis in case 1. (A) Anatomical location of a large palpable mass in the right breast with retracted skin. (B) A well-defined hypoechoic area with non-homogenous echotexture on breast ultrasound. (C) A circumscribed radiopaque lesion with a mostly sharp contour and indeterminate dorsal demarcation in X-ray digital mammography.

Figure 2.

Breast fibromatosis in case 1. Computed tomography thoracic scan in the axial view showing a large tumor mass in the right breast involving the chest wall.

Figure 3.

Breast fibromatosis in case 1. (A) Right chest wall defect created by the en bloc resection of the underlying chest wall structures (fourth and fifth ribs, intercostal muscles and parietal pleura). (B) The defect was then closed with a flat sheet of polypropylene mesh.

Figure 4.

Breast fibromatosis in case 1. (A) Poorly circumscribed tumor with infiltration of the adjacent tissue, including muscle, in gross examination. (B) A predominant spindle cell proliferation of bipolar fibroblasts and myofibroblasts with low mitotic activity, without cell atypia upon hematoxylin and eosin staining (magnification, ×200). (C) Upon immunohistochemical staining (magnification, ×200), diffuse nuclear β-catenin positivity in fibromatous proliferation was present. (D) In total, <5% of the spindle cells were positive for Ki-67 (MIB1).

Figure 5.

Breast fibromatosis in case 2. (A) Mammographic and (B) ultrasound examinations suggested an invasive breast tumor, probably carcinoma, infiltrating the muscles of the chest wall. (C) The patient underwent a quadrantectomy with a partial resection of the underlying musculature.

Figure 6.

Breast fibromatosis in case 2. (A) Gross sectional view of the pathology specimen. (B) High-power histological view showing fibromatosis invading into the adjacent skeletal muscle (hematoxylin and eosin; magnification, ×400). (C) Diffuse nuclear β-catenin positivity and (D) low Ki-67 (MIB1) positivity in fibromatous proliferation (magnification, ×200).