Fibromatosis of the breast. Report of two cases and review of the literature

Background: Fibromatosis is a term used to describe a group of lesions characterized by well-differentiated fibroblast proliferation with an usually benign biological behavior but with an infiltrative pattern of growth, frequently recurrent and locally invasive. It is generally localized in the retroperitoneal area, neck and extremities. The presence of this entity in breast tissue is an uncommon clinical situation, comprising similar to 0.2% of breast tumors and very often misdiagnosed as malignant disease or phyllodes tumor. In this rare condition, immunohistochemistry is an important diagnostic tool in anatomopathological differential diagnosis with other spindle cell tumors of the breast. The purpose of this paper is to report the experience with two cases of this rare condition. Clinical cases: We present two cases of breast fibromatosis confirmed immunohistochemically and also by biopsy. One case had the clinical and imaging appearance of breast carcinoma with the classic irregular mass presentation and the other case was misdiagnosed as phyllodes tumor because of the size and density of the tumor and the cytology. Conclusions: Approximately 83 cases of breast fibromatosis have been reported during the last 30 years, including one male patient. We reviewed clinicopathological features of two cases of fibromatosis of the breast treated at our institute.