Percutaneous core biopsy of the breast: effect of operator experience and number of samples on diagnostic accuracy.

OBJECTIVE: The purpose of our study was to assess the degree of operator experience and the number of core biopsy samples required to achieve an accurate histologic diagnosis for each of five common mammographically defined lesions, using percutaneous core breast biopsy performed on a dedicated prone biopsy table.

SUBJECTS AND METHODS: A prospective multisite study was performed that involved nine institutions (academic and private) with experienced breast radiologists and the use of dedicated prone biopsy table units with digital assistance and standardized protocol. Asymptomatic women evaluated during a 2-year study period were assigned a mammographic diagnosis reported in a manner prescribed by the American College of Radiology Breast Imaging Reporting and Data System lexicon. Mammographic lesions evaluated included masses, masses with calcifications, clustered calcifications, focal asymmetries, and architectural distortions. Where histologic diagnosis was indicated, core biopsy was performed with five individual samples obtained and sequentially analyzed. Two hundred thirty patients had immediate excisional biopsy, the results of which provided the basis for a statistical analysis to compare the accuracy of each sequential core biopsy sample with surgical results. Statistical analysis was also done to ascertain the accuracy of core biopsy diagnosis as a function of operator experience.

RESULTS: Trends toward increasing accuracy were observed by increasing the number of core biopsies for each of five types of mammographically defined lesions, especially for clustered calcifications. Statistically significant increased accuracy was observed when the number of biopsies was increased beyond one (p = .003). Trends toward increased accuracy with more experience were observed for all lesions, especially for calcifications. Of the 230 lesions studied with immediate surgical validation, more than 80% of all lesions except clustered calcifications (75%) were diagnosed on the basis of two core biopsies; accuracy after five biopsies was 98% for masses, 91% for calcifications, 100% for masses with calcification, 100% for focal asymmetries, and 86% for architectural distortions.

CONCLUSIONS: Accuracy of diagnosis based on the results of percutaneous core breast biopsy improved with an increase in the number of core biopsy samples obtained for any given lesion seen on mammograms and with increased experience in performing the procedure. Five samples yielded an overall diagnostic accuracy of 97%. Familiarity with expected accuracy from this procedure for different mammographic lesions and following increased experience may assist physicians in planning patient management.