Purpose: To determine how often lesions diagnosed as benign with stereotactic core-needle biopsy (SCNB) change at follow-up mammography and to determine the optimal follow-up strategy and the delayed false-negative rate.
Materials and methods: From July 1992 through December 1995, 355 of 540 cases (66%) in which SCNB yielded benign results were managed with follow-up mammography. Mammographic follow-up was available for 298 of these cases (84%). Follow-up mammography reports were reviewed. When a change was reported, pre- and postbiopsy mammograms, pathology reports, and results of subsequent mammographic follow-up were reviewed.
Results: Mammographic change occurred in 21 of 298 cases (7%) at intervals of 6-55 months (mean, 20 months). Change occurred after initial mammographic stability in 10 of 21 cases. Repeat biopsy was performed in 18 of 21 cases. Malignancy was diagnosed in two cases: one mass that changed at 6 months and one case of microcalcifications that changed at 24 months. This represented a delayed false-negative rate of 2% (two of 105 malignancies among 540 biopsies).
Conclusion: A small percentage of cases diagnosed as benign with SCNB will change on follow-up mammograms, which may necessitate repeat biopsy. These results suggest that 6-month follow-up for cases that yield nonspecific benign results at SCNB and yearly screening mammography for cases with specific benign results is a reasonable management strategy.