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Because misclassification of breast biopsies is relatively common, and no prior study had analyzed strategies for reducing error, the recent Elmore study is timely [1]. Here, 12 different strategies for acquiring second opinions were compared in order to help define which strategies worked best to reduce misclassification errors. The authors systematically tested whether and which pathology classification affected the best strategic choice for: invasive breast cancer, ductal carcinoma in situ (DCIS), atypia, proliferative without atypia, or benign without atypia. Also analyzed was the influence of the perceived case difficulty, the pathologists’ clinical volumes, and local institutional policy.

The test sample consisted of a set of 240 histopathology slides (one per case) that had previously undergone expert consensus to form a reference diagnosis. A total of 115 pathologists were assigned to one of four groups of 60 slides distributed according to the range of outcomes usually found. Each pathologist independently interpreted all 60 slides from one of the four sets of 60 breast biopsy specimens. The key findings were: (1) Over-interpretation of benign cases without atypia was cut in half (12.9% to 6.0%) by second opinions when initial diagnosis of atypia, DCIS and invasive cancer always included a second opinion; (2) atypia cases had the highest misclassification rate after a single interpretation (52.2%) which remained at more than 34% in every second opinion strategy tested; (3) excluding invasive breast cancer slides, the misclassification rates decreased (p < 0.001) from 24.7% to 18% when all of these received a second opinion; (4) high-volume pathologists (> nine cases per week) consistently delivered fewer misclassifications; (5) accuracy of diagnosis improved by the second opinion regardless of the pathologists’ confidence in their experience or diagnosis.


  • Winnifred Cutler
    Athena Institute for Women’s Wellness, Chester Springs, PA, USA
  • James Kolter
    Philadelphia College of Osteopathic Medicine, Philadelphia, PA, USA


  1. Elmore JG, Tosteson AN, Pepe MS, Longton GM, Nelson HD. Evaluation of 12 strategies for obtaining second opinions to improve interpretation of breast histopathology: simulation study. BMJ 2016;353:i3069
  2. Jorgensen KJ, Gotzsche PC. Overdiagnosis in publicly organized mammography screening programmes: systematic review of incidence trends. BMJ 2009;339:1-8
  3. Gilbert Welch HG, Prorok PC, O’Malley AJ, Kramer BS. Breast-cancer tumor size, overdiagnosis, and mammography screening effectiveness. N Engl J Med 2016;375:1438-47
  4. Jørgensen KJ, Gøtzsche PC, Kalager M, Zahl PH. Breast cancer screening in Denmark: a cohort study of tumor size and overdiagnosis. Ann Intern Med 2017 Jan 10. Epub ahead of print
  5. Brawley OW. Accepting the existence of breast cancer overdiagnosis. Ann Intern Med 2017 Jan 10. Epub ahead of print
  6. Darby SC, Ewertz M, McGale P, et al. Risk of ischemic heart disease in women after radiotherapy for breast cancer. N Engl J Med 2013;368:987-98
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