Audit of mammography in a community setting.

A Northwest community concentrated all mammography services in one location and instituted a program of annual review. The 32,118 mammograms prompted 466 biopsies of women who had no palpable abnormality. Over the 5-year study, there were 142 nonpalpable cancers found for a positive biopsy rate of 30%. In the first year, the positive biopsy rate was 17%, and, in the last year, it was 42%. The increase in apparent selectivity prompted a search for false negatives or missed breast cancers. One percent of women subjected to mammography underwent biopsy, but, interestingly, only 84% of women undergoing mammography received a normal report. Eighty-seven percent of the cancers were invasive, and 13% were considered to be noninvasive. A review of the literature suggests significant variation in the frequency of identifying nonpalpable breast cancer, and respected pathologists report variations in the pathologic evaluation of these nonpalpable cancers.