Objective: To characterize the mammographic and US features of focal fibrosis of the breast and to estimate the false negative rate for breast cancer when focal fibrosis was diagnosed by CNB.

Material and Method: The subjects were 82 patients diagnosed fibrosis of the breast by CNB during 7-year period.

Results: Of 38 mammographic visible lesions there were mass lesions in 12 (32%), calcifications in 14 (37%), mass with calcifications in four (11%), architectural distortion in one (3%) and asymmetrical density in seven (18%). Most of the lesions seen on the US were hypoechoic mass (81%). The suspicious features, which warrant CNB, included irregular shape in 37 (55%), indistinct margin in 38 (57%), and posterior shadowing in 28 (42%). Most of the lesions were categorized as Breast Imaging Reporting and Data System (BI-RADS) 4A (59%). Thirteen cases underwent surgical biopsy and all showed benign pathologic results. No false-negative cases were detected.

Conclusion: Focal fibrosis had some features similar to malignant lesion. CNB showed reliable pathological result. No false negative result was found in the present study.

Keywords: Breast, Focal fibrosis, Core needle biopsy, Mammogram, Ultrasound