Bilateral breast fibromatosis after silicone prosthetics in a patient with classic familial adenomatous polyposis: A case report.

Breast fibromatosis is a benign fibroblastic proliferation accounting for less than 0.2% of breast tumors. It presents sporadically or as a manifestation of familial adenomatous polyposis (FAP). Fibromatosis in FAP may develop in patients with adenomatous polyposis coli (APC) gene mutations at any location through the gene. Notably, there is an increased risk if mutation is downstream codon 1400. The present case report described a 33-year-old woman with recurrent bilateral breast fibromatosis after breast implants in a context of classic FAP. APC mutation (codon-935) was detected at the age of 16. In the same year, a thyroidectomy for a cribriform-morular papillary thyroid carcinoma (pT1) was performed. Seven years later, a prophylactic total colectomy with >100 adenomas without invasive carcinoma was performed and the patient was kept under surveillance. At the age of 30 years old, she underwent breast silicone implantation for cosmetic reasons. One year later, bilateral breast tumors were diagnosed in core biopsy as fibromatosis (nuclear -catenin+, estrogen receptors-). After no success with medical treatment with tamoxifen, bilateral mastectomy was performed. The patient relapsed one year later and a fibromatosis lesion in the right thoracic wall was excised again. The patient demonstrated no signs of relapse 24 months after the surgery. This rare case illustrates that the increased risk of developing fibromatosis in patients with FAP, even in the classic form, should be considered before deciding to place breast implants.