Objective: Focal fibrosis is a benign breast lesion commonly diagnosed by imaging-guided core biopsy. The goal of this study is to determine the frequency of focal fibrosis diagnosed at core biopsy and to describe its imaging features.
Materials and methods: A consecutive series of 894 imaging-guided breast core biopsies were reviewed, and all cases of focal fibrosis were selected. The imaging features of each lesion were characterized. All lesions had been reviewed during radiologic-histologic review sessions to assess for accurate needle positioning and concordant results. Follow-up imaging and histologic data were reviewed to document lesion stability.
Results: Focal fibrosis was diagnosed in 80 (8.9%) of 894 imaging-guided core biopsies: 20 (8.7%) of 229 sonographically guided biopsies and 60 (9.0%) of 665 mammographically guided biopsies. Of 75 mammographically visible lesions, 39 (52%) were masses, 29 (39%) were densities, and seven (9.3%) were clusters of calcifications. Thirty-five hypoechoic lesions were visualized on sonography: 29 (80%) were oval, and six (17%) were irregularly shaped. Six (21%) of the 28 oval masses showed posterior enhancement, four (14%) posterior shadowing, and 19 (68%) neither feature. Fifty-two (65%) of 80 patients with focal fibrosis had routine imaging follow-up; all had stable findings (mean follow-up period, 27 months). No false-negative cases were identified.
Conclusion: Focal fibrosis most commonly appears as an enlarging solid mass or developing density on mammography or as an oval mass on sonography. Our data suggest that focal fibrosis accounts for 9% of lesions that undergo imaging-guided core biopsy and that the diagnosis can be accurately reached using imaging-guided biopsy.