Focal fibrosis: a common breast lesion diagnosed at imaging-guided core biopsy

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.

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.

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.

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.