Desmoid breast fibromatosis occurring after reconstructive surgery simulating carcinoma: A rare case report

Abstract

Introduction: Desmoid fibromatosis is a rare tumor, representing less than 0.2% of all breast tumors, characterized by
clonal fibroblastic deep soft tissue, locally aggressive growth and high incidence of recurrence (between 24% and 77%
in 10 years). It is associated with trauma or surgical procedures of the breast and presents similary to breast carcinoma.
Diagnostic criteria are histological, and breast imaging techniques are non-specific. The treatment is surgical with complete excision and safety margin, varying according to the studies, from 0.5 to 3 cm to avoid recurrences, which, when they
occur and reach vital organs, cause 8% of mortality. Case Report: A female, 56 years old, with infiltrating ductal carcinoma
in the upper lateral quadrant of the left breast, measuring 2.0 cm, high nuclear grade, triple-negative, and acquired at the
age of 53 years. She underwent neoadjuvant chemotherapy, quadrantectomy with negative sentinel lymph node biopsy,
and radiotherapy. Two years later, she returned with a recurrence in the lower lateral quadrant of the left breast, measuring 1.0 cm. Despite the negative genetic study for pathogenic variants, she opted for bilateral mastectomy and immediate reconstruction (prostheses and dermal matrix), the one on the right being prophylactic. There was infection on the
right, rejection, and loss of the prosthesis. After 1 year, she presented with a bearable nodule, immobile and adhered to the
chest wall, measuring 2.2 cm on the lateral border of the pectoral muscle, on the right, confirmed by chest tomography
and magnetic resonance imaging. She was submitted to mammotomy whose biopsy showed low-grade spindle cell in the
inferolateral quadrant. A segmental resection was performed, whose anatomopathological and immunohistochemical
studies confirmed the diagnosis of fibromatosis in the right breast, positive reaction to the beta-catenin antibody, measuring 2.5×2.5 cm and free elastic margins. She is being followed up at the outpatient clinic, with no signs of recurrence.