1. High agreement between individual pathologists and reference consensus diagnoses was observed for the verification of invasive breast cancer and benign without atypia.
2. Variability in pathologists’ interpretations led to overdiagnoses of atypia and ductal carcinoma in situ when compared to reference consensus diagnoses.
Evidence Rating Level: 2 (Good)
Study Rundown: The Breast Pathology Study evaluates diagnostic agreement between pathologists in their interpretation of breast biopsy slide specimens. This analysis aimed to apply the results to patient populations by estimating how diagnostic variability affects accuracy of breast biopsy specimen interpretation. Generally, the authors observed that the vast majority of individual pathologist interpretations of breast biopsy specimens of women included in the study would likely agree with the interpretations of the reference consensus panel. High accuracy was observed among women diagnosed with benign without atypia and invasive breast cancer. However, significant variation was observed among diagnoses of atypia and ductal carcinoma in situ (DCIS), where both were overdiagnosed by individual pathologists when compared to the reference. This study is limited by several factors. First, although the reference consensus panel was composed of three expert opinions, there is no guarantee that this panel represents a truly accurate diagnosis. Furthermore, as this analysis assessed women screened using film mammography, results may differ with newer technologies. Overall, this study highlights that while interpretation of invasive breast cancer and benign cases without atypia are highly accurate, reference diagnosis verification for DCIS and atypia may be much lower.
In-Depth [population study]: In this study, the authors assessed the probability that a pathologist’s interpretation of a single diagnostically representative breast biopsy slide would accord with a consensus-based reference standard derived from 3 expert breast pathologists interpreting the same slide. The predictive values were calculated with Bayes’ theorem, utilizing results from the Breast Pathology Study, as well as published data on the prevalence of breast pathology diagnoses in women aged 50 to 59 from the Breast Cancer Surveillance Consortium. It was observed that confirmation of pathologists’ interpretations by the expert reference consensus panel would occur in 92.3% (95%CI 91.4% to 93.1%) of biopsies overall. Furthermore, for women receiving a diagnosis of benign without atypia or invasive breast cancer, the analysis indicated 97.1% (95%CI 96.7% to 97.4%) and 97.7% (95%CI 96.5% to 98.7%) diagnostic agreement, respectively, between individual pathologists and the reference panel. In contrast, only 37.8% accordance was observed for diagnoses of atypia (95%CI 33.6% to 42.7%) and 69.6% for DCIS (95%CI 64.4% to 75.3%).
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