Fibromatosis of the Breast: Report of a Case with Cytohistological Correlation

Background: Breast fibromatosis is a rare, locally infiltrative lesion without metastatic potential that arises from either stromal fibroblasts or myofibroblasts of the breast or the pectoral fascia, extending into the breast, with its cytological and histological features only rarely been described. Case Presentation: A ۵۸-year-old woman, with no past medical/surgical or family history, was diagnosed on regular mammographic and ultrasound examination with a nodular tumor density, in the upper inner part of her right breast. There were no calcifications or apparent lymph nodes in the right axilla. The woman underwent FNA and US-guided biopsy and final resection biopsy under hook marking. We reviewed the cytological findings of fibromatosis of the breast, as they presented in FNAC aspirates of a non-palpable mammographic finding and the histological findings in both preoperative core-needle biopsy and excision specimen. The final diagnosis was of fibromatosis of the breast. No further actions were taken. The woman is well, without recurrence, more than four years afterwards. Conclusion: The diagnosis in the presented patient can make the pathologists more acquainted with the cytological and pathologic features of a rare tumor entity and the clinicians with a rare breast lesion, which can mimic malignancy both clinically and radiologically. The diagnosis of fibromatosis of the breast is more reliable in excision specimens. Nevertheless, cytology can be an invaluable adjunct to histology, pre-operatively, as it can exclude cancer and help in the preoperative planning.