1. Agreement in interpretation of breast biopsies between a panel of three expert pathologists and 115 practicing pathologists was 75.3% in this study.
2. In this study, agreement was highest in cases of invasive carcinoma and lowest in cases of atypia.
Evidence Rating Level: 1 (Excellent)
Study Rundown: Breast biopsies represent an important component of the workup of breast lesions that may be concerning for malignancy, with pathologic diagnoses playing an important role in the planning of treatment and surveillance. While guidelines for pathologic diagnosis exist, it is unknown how reproducible diagnoses are between pathologists. This study sought to determine the degree of concordance between US pathologists in reading breast biopsy samples by comparing the interpretation of breast biopsies between a panel of three expert pathologists and 115 practicing pathologists. Concordance between the three expert pathologists was 75%, while agreement between the participating pathologists and the reference diagnosis was 75.3%. Agreement was higher for invasive carcinoma than for atypia and ductal carcinoma in-situ.
Strengths of this study include the systematic way in which the reference diagnosis was determined, the way in which cases were randomized, the inclusion of cases along the spectrum of pathologic diagnoses, and the diversity of participating pathologists. One weakness of the study is the fact that pathologists were only given one slide, whereas in practice pathologists can view several slides and can obtain additional stains to aid in diagnosis. Ultimately, this study presents important data on the rate of agreement between pathologists, but further studies should be done to determine how this might impact the overall clinical outcome of patients.
In-Depth [randomized controlled study]: This study randomized 115 pathologists to review one of four sets of 60 breast biopsy slides and to render a diagnosis. The slides were previously reviewed by a three pathologist expert panel and the agreement between the 115 pathologists and the expert panel was calculated. The expert panel unanimously agreed on the diagnosis in 75% of cases. Agreement between the participating pathologists and the expert panel was 75.3% (95%CI 73.4% to 77.0%). Over-interpretation or under-interpretation of slides was distributed among all pathologists and all cases. Agreement was highest in cases of invasive carcinoma (96%; 95%CI 94% to 97%) and was lowest in cases of atypia (48%; 95%CI 44%-52%). Multivariate analysis showed that pathologists with lower case volumes, nonacademic practices, and smaller practices were less likely to agree with the reference diagnosis. Multivariate analysis also showed that disagreement was highest in women with dense breast tissue and that over-interpretation rate was highest and under-interpretation was lowest in breast biopsies from women in their 40s.
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