Mammography screening--reasons for recall and the influence of experience on recall in the Finnish system.

The reasons for recall and the influence of experience on recall were studied in 579 women (3.21%) recalled from mammography screening. The proportion of recalls for further studies was the greatest (6.30%) at the onset of screening. With increased experience, the proportion decreased by stages and in the second screening round it was only 2.04%. The proportion of cases referred for surgical biopsy in the first screening round was 0.7% and the proportion of screening-detected breast cancers was 0.52%. These change little with increasing experience. In the second screening round, however, the proportion of referrals for surgical biopsy (0.43% of those screened) and of screening-detected breast cancers, (0.30%) were both low. A tumour-like density was the commonest finding resulting in recall for further studies, and the number caused by superimposition of normal parenchymal structures decreased with experience, while the proportion of breast cancers and benign tumours increased. The proportion of cases with parenchymal distortion resulting in recall for further studies was similar in both screening rounds but the number of those referred for biopsy fell dramatically in the second screening round. The number of recalls for microcalcification also fell with experience and the proportion of breast cancers in this group increased over the two screening rounds. A high ratio of malignancies in surgical biopsies can be expected when the radiologists undertaking primary screening also perform all further studies.