Primary Fat-forming solitary fibrous tumor with focal atypical features of the breast. A case report and literature review

Abstract Background: Primary solitary fibrous tumor (SFT) in breast is rare, while breast fat-forming solitary fibrous tumor (FFSFT) is even more rare in clinic. Here we reported a case of FFSFT with focal atypical features of the left breast, and present the clinicopathological features, molecular features and pathological diagnosis.Case presentation: A 51-year-old female patient underwent breast surgery in clinic of our hospital with a 6 month of a palpable painless left breast mass. Imaging examination of the breast revealed a 3.4 cm ×1.9 cm ×1.7 cm solid mass originating from her left breast. Then the patient underwent left breast lumpectomy in the tumor area, and postoperative pathological result confirmed the diagnosis of FFSFT with focal atypical features deriving from breast. The additional treatment such as chemotherapy or radiotherapy were not provided. The patient remains with no evidence of disease recurrence or metastasis in 3 months of follow-up. Conclusion: Primary breast FFSFT is very rare and easy to be confused with other soft tissue tumors. The definitive diagnosis of primary breast FFSFT should base on histopathological morphology, immunophenotype and molecular detection.