Clinicopathological analysis of three cases of breast desmoid-type fibromatosis

Breast desmoid-type fibromatosis is a rare, locally aggressive but non-metastatic mesenchymal tumor according to WHO classification, characterized by spindle cell proliferation with irregular infiltrative borders. Its morphological overlap with other spindle cell lesions necessitates careful differential diagnosis. It’s worth noting that multifocal breast desmoid-type fibromatosis has not been reported. We present three breast desmoid-type fibromatosis cases diagnosed at Women and Children’s Hospital of Chongqing Medical University (Oct 2022-Sep 2024) in females aged 15–42 years (mean ± standard deviation: 31.3 3 ± 11.73 years; median 37 years). All patients were asymptomatic. A 37-year-old female who was diagnosed with familial adenomatous polyposis (FAP) 5 years ago presented with multifocal lesions. One case co-occurred with low nuclear grade ductal carcinoma in situ (DCIS) and fibroadenoma. Ultrasonography revealed circumscribed margins in two instances and ill-defined margins in one case. Surgical management included vacuum-assisted excision (two cases) and combined breast-conserving surgery for the carcinoma-associated case. To our knowledge, this is the first report of multifocal breast desmoid-type fibromatosis and its co-occurrence with fibroadenoma and low nuclear grade DCIS. Through integrated clinicopathological, immunohistochemical, and molecular analyses supplemented by a systematic literature review, we delineate diagnostic criteria, therapeutic approaches, and prognostic indicators. These findings provide critical insights to reduce diagnostic errors and enhance precision in managing this challenging entity.