Prevalence and type of incidental extramammary findings in MRI of the breast

Abstract

To analyze prevalence and type of relevant incidental findings in patients undergoing breast MRI. This prospective investigation consists of 1013 patients who underwent breast MRI as follow-up after breast cancer therapy, for pre-operative staging, and for screening of high-risk patients as well as for clarification of unclear clinical examinations and inconclusive conventional mammography. Prevalence and type of relevant incidental extramammary findings were recorded together with the indication of the examination. Incidental extramammary findings were encountered in 92 (9%) of the 1013 patients. MRI had markedly more incidental extramammary findings with the staging examinations (39.5%) and follow-up examinations (11.6%). The prevalence of incidental malignant findings was 81% in patients examined for pre-operative staging. Incidental benign and malignant findings were equally frequent in patients followed after breast cancer therapy. The incidental findings were exclusively benign in patients without a history of breast cancer. The interpretation of breast MRI should incorporate a careful analysis of the adjacent extramammary structures. Especially patients followed after breast cancer therapy can be expected to have incidental malignant findings outside the breast.