Breast fibromatosis is a benign breast tumor of mesenchymal origin, accounting for 0.2% of breast tumors. This study reports two cases of breast fibromatosis highlighting its diagnostic, morphological, therapeutic and evolutionary features. In both cases, this tumor clinically and radiologically mimicked a cancer. Diagnostic confirmation was based on histological examination. Breast fibromatosis was characterized by local progression and a tendency to recurrence, hence the role of surgical excision with free surgical margins in our patients. The role of locoregional treatments (radiotherapy and cryotherapy) and medical treatments, in particular anti-estrogen therapy, is not clearly defined. In conclusion, breast fibromatosis must be known as it mimicks breast cancer and is characterized by a very high recurrence rate, without ever developing metastases.

Fibromatosis of the breast is a rare benign disease compromising <0.2% of all primary breast tumors. Although the chest wall is a common location, occurrences of implant-associated fibromatosis of the breast are extremely rare; only 33 cases have been reported. We present a case of a 42-year-old female who underwent breast augmentation with silicone breast implants, and 2 years later developed an aggressive implant-associated fibromatosis of the breast and chest wall. On imaging studies, the tumor mimicked breast carcinoma, and despite chemotherapy, the fibromatosis rapidly enlarged and was locally invasive requiring wide surgical excision. Unlike previously reported imaging findings, magnetic resonance imaging revealed an oval circumscribed mass with fringe-like internal architecture. We provide a review of the literature and discuss the imaging features of implant-associated fibromatosis of the breast.

BACKGROUND: Desmoid tumor of the breast is very rare and locally aggressive but has no distant metastasis. Bilateral lesions are extremely rare, found in only 4% of patients. Two cases of bilateral desmoid tumor of the breast are reported. The clinical presentation, diagnosis, imaging, treatment, and follow-up outcomes of recurrence as well as a brief literature review are provided.
METHODS: Case 1 is a 31-year-old woman who presented with nipple retraction. An ultrasound revealed BIRAD V in both breasts. She underwent a bilateral excisional biopsy under ultrasound mark with the pathology result of extra-abdominal desmoid tumor in both breasts. The patient had a bilateral mastectomy with silicone implantation due to the involved margins by excision. She remained tumor free after 7-year follow-up. Case 2 is a 28-year-old woman who presented with a lump on her right breast that she had discovered ~2 months earlier. An ultrasound showed a spiculated mass in the right breast and some circumscribed hypoechoic masses in both breasts. A bilateral breast excision was done. The pathology result was an extra-abdominal desmoid tumor. She had recurrence on both sides and underwent a mastectomy and silicone implantation. The tumor has not recurred after 1-year follow-up.
CONCLUSIONS: Imaging cannot distinguish between benign breast lesions and malignancy. Pathology results are helpful in making a definitive diagnosis. Given that the desmoid tumor is locally aggressive, a local excision with clear margins is recommended. Chemotherapy and hormonal treatment are controversial.

Breast fibromatosis is a rare entity responsible for 0.2% of all solid breast tumors. It has been associated with scars, pregnancy, implants, and familial adenomatous polyposis. We present an interesting case of breast fibromatosis in a 29 year old woman which encroached upon her saline implant and subsequently filled its cavity once the implant was removed. The patient was put on tamoxifen therapy and at 14 month follow-up there was a significant decrease in the size of the mass. Dynamic MRI images are offered for review and current treatment options are discussed.