The predictive value of certain mammographic signs in screening for breast cancer.

Prospective evaluation of aggressive screening for breast cancers which are either 5 mm in size or, alternatively, wholly intraductal or in situ lobular, was performed. Twenty-one percent of all cancers were identified by the presence of microcalcifications; 71% of these were minimal and the predictive value of microcalcifications was 11.5% (+/- 1.7). The probability of cancer given a radiographically benign, dominant mass over 1 cm in size, palpable or not, was 2% (+/- 0.8) and two-thirds of these cancers were minimal. If diagnosis had not been established by biopsy for these benign appearing lesions six percent of all cancers would not have been detected. Had clinical examination been omitted from screening, 32 cancers (16%) would have been eliminated, 13 of which were minimal. However, the false-positive rate would have been halved. The range of predictive values, true-positive rates, and percent of minimal cancers detected are presented for each of several mammographic signs when clinical examination was either positive or negative.