Stereotactic breast biopsy: an audit of 18 months at BreastScreen Auckland

Stereotactic biopsy has become a widely used technique for marnmographically detected lesions that are clinically and sonographically occult. Vacuum-assisted (mammotome) biopsy on a dedicated prone stereotactic unit has further increased ease of biopsy and utility of the technique. Results of an 18-month audit in the national breast screening programme (BreastScreen Auckland and North) in the Auckland region demonstrates results comparable with those achieved elsewhere. Of a total of 399 stereotactic biopsies, 23 were excluded as they were 14-G core biopsies rather than 11-G mammotome biopsies. Of 376 mammotome biopsies, 10 (2%) failed, 266 (70.7%) were benign, 39 (10.3%) were atypical ductal hyperplasia (ADH) and 70 (18.6%) were malignant. Of these, 14.6% were ductal carcinoma in situ (DCIS) and 4% were invasive carcinomas. All cases diagnosed as ADH underwent formal excision biopsy. Of the 39 cases, 33 demonstrated benign disease or residual ADH only on excision (84.6%) and six (15.4%) patients were upgraded: five to DCIS and one to invasive carcinoma. The significant complication rate was 0.5%. Indications for biopsy were calcification in 89% of cases, mass lesions in 10.6% of cases and architectural distortion in 0.2% of cases. The failure rate of 2% compares with hookwire biopsy series. Practical issues and protocols have been presented.