Clinical outcome of doubtful mammographic findings

We performed this study to determine whether subthreshold findings of malignancy can be detected prospectively during interpretation of routine mammographic screenings.

For several years we have marked with crayon mammographic findings identified at screening that may represent precursor lesions but that we judge so likely to be benign that further workup is not indicated. The crayon marks prompt a closer look at the designated area on the next screening examination. We reviewed all screening examinations performed between August 1991 and October 1992 for which we had done prior normal screening. The prior mammograms were examined for crayon marks that indicated possible precursor lesions, and outcome was assessed on the basis of findings of subsequent screenings.

Crayon marks of 543 findings (382 women) were identified on prior normal examinations in the 5514 cases reviewed. Marked findings consisted of calcifications (48%), noncalcified nodules (22%), vague densities (18%), asymmetries (7%), combination findings (2%), and possible architectural distortions (2%). On subsequent examination (mean interval, 30 months; range, 231 days to 90 months), 74% of marked findings showed no significant change, 21% were less apparent or had disappeared, 4% were slightly more apparent but still within normal limits, and six cases (1%) were interpreted as abnormal, which resulted in diagnostic workup. Three of the six latter cases were judged to be benign after further imaging evaluation; the other three patients underwent biopsy. One of these cases resulted in a diagnosis of low-grade ductal carcinoma in situ; the other two findings were benign. No unsuspected cancers were found after linkage with our tumor registry 1 year after the most recent examination with crayon marks.

This study shows that almost all prospectively marked benign-appearing findings are benign and inconsequential. The medicolegal implications of this observation include the inappropriateness of malpractice claims in cases in which cancer could not reasonably be detected prospectively.