title: Diagnostic concordance among pathologists interpreting breast biopsy specimens.
abstract: OBJECTIVE
  A breast pathology diagnosis provides the basis for clinical treatment and management decisions; however, its accuracy is inadequately understood.
  
  
  OBJECTIVE
  To quantify the magnitude of diagnostic disagreement among pathologists compared with a consensus panel reference diagnosis and to evaluate associated patient and pathologist characteristics.
  
  
  METHODS
  Study of pathologists who interpret breast biopsies in clinical practices in 8 US states.
  
  
  METHODS
  Participants independently interpreted slides between November 2011 and May 2014 from test sets of 60 breast biopsies (240 total cases, 1 slide per case), including 23 cases of invasive breast cancer, 73 ductal carcinoma in situ (DCIS), 72 with atypical hyperplasia (atypia), and 72 benign cases without atypia. Participants were blinded to the interpretations of other study pathologists and consensus panel members. Among the 3 consensus panel members, unanimous agreement of their independent diagnoses was 75%, and concordance with the consensus-derived reference diagnoses was 90.3%.
  
  
  METHODS
  The proportions of diagnoses overinterpreted and underinterpreted relative to the consensus-derived reference diagnoses were assessed.
  
  
  RESULTS
  Sixty-five percent of invited, responding pathologists were eligible and consented to participate. Of these, 91% (N = 115) completed the study, providing 6900 individual case diagnoses. Compared with the consensus-derived reference diagnosis, the overall concordance rate of diagnostic interpretations of participating pathologists was 75.3% (95% CI, 73.4%-77.0%; 5194 of 6900 interpretations). Among invasive carcinoma cases (663 interpretations), 96% (95% CI, 94%-97%) were concordant, and 4% (95% CI, 3%-6%) were underinterpreted; among DCIS cases (2097 interpretations), 84% (95% CI, 82%-86%) were concordant, 3% (95% CI, 2%-4%) were overinterpreted, and 13% (95% CI, 12%-15%) were underinterpreted; among atypia cases (2070 interpretations), 48% (95% CI, 44%-52%) were concordant, 17% (95% CI, 15%-21%) were overinterpreted, and 35% (95% CI, 31%-39%) were underinterpreted; and among benign cases without atypia (2070 interpretations), 87% (95% CI, 85%-89%) were concordant and 13% (95% CI, 11%-15%) were overinterpreted. Disagreement with the reference diagnosis was statistically significantly higher among biopsies from women with higher (n = 122) vs lower (n = 118) breast density on prior mammograms (overall concordance rate, 73% [95% CI, 71%-75%] for higher vs 77% [95% CI, 75%-80%] for lower, P < .001), and among pathologists who interpreted lower weekly case volumes (P < .001) or worked in smaller practices (P = .034) or nonacademic settings (P = .007).
  
  
  CONCLUSIONS
  In this study of pathologists, in which diagnostic interpretation was based on a single breast biopsy slide, overall agreement between the individual pathologists' interpretations and the expert consensus-derived reference diagnoses was 75.3%, with the highest level of concordance for invasive carcinoma and lower levels of concordance for DCIS and atypia. Further research is needed to understand the relationship of these findings with patient management.
authors.affiliation: Department of Medicine, University of Washington School of Medicine, Seattle.
authors.forename: Joann G
authors.initials: JG
authors.lastname: Elmore
authors.affiliation: Program in Biostatistics and Biomathematics, Fred Hutchinson Cancer Research Center, Seattle, Washington.
authors.forename: Gary M
authors.initials: GM
authors.lastname: Longton
authors.affiliation: Department of Family Medicine, Oregon Health and Science University, Portland.
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Carney
authors.affiliation: Department of Family Medicine, University of Vermont, Vineyard Haven, Massachusetts.
authors.forename: Berta M
authors.initials: BM
authors.lastname: Geller
authors.affiliation: Department of Community and Family Medicine, The Dartmouth Institute for Health Policy and Clinical Practice, Geisel School of Medicine at Dartmouth, Norris Cotton Cancer Center, Lebanon, New Hampshire.
authors.forename: Tracy
authors.initials: T
authors.lastname: Onega
authors.affiliation: Department of Community and Family Medicine, The Dartmouth Institute for Health Policy and Clinical Practice, Geisel School of Medicine at Dartmouth, Norris Cotton Cancer Center, Lebanon, New Hampshire6Department of Medicine, Geisel School of Medicine at.
authors.forename: Anna N A
authors.initials: AN
authors.lastname: Tosteson
authors.affiliation: Providence Cancer Center, Providence Health and Services Oregon, Portland8Department of Medical Informatics and Clinical Epidemiology, Oregon Health and Science University, Portland9Department of Clinical Epidemiology and Medicine, Oregon Health and Scien.
authors.forename: Heidi D
authors.initials: HD
authors.lastname: Nelson
authors.affiliation: Program in Biostatistics and Biomathematics, Fred Hutchinson Cancer Research Center, Seattle, Washington.
authors.forename: Margaret S
authors.initials: MS
authors.lastname: Pepe
authors.affiliation: Department of Pathology, Stanford University School of Medicine, Stanford, California.
authors.forename: Kimberly H
authors.initials: KH
authors.lastname: Allison
authors.affiliation: Department of Pathology, Beth Israel Deaconess Medical Center, Boston, Massachusetts12Harvard Medical School, Boston, Massachusetts.
authors.forename: Stuart J
authors.initials: SJ
authors.lastname: Schnitt
authors.affiliation: Department of Laboratory Medicine and the Keenan Research Centre of the Li Ka Shing Knowledge Institute, Toronto, Ontario, Canada14St Michael's Hospital and the University of Toronto, Ontario, Canada.
authors.forename: Frances P
authors.initials: FP
authors.lastname: O'Malley
authors.affiliation: Department of Pathology and University of Vermont Cancer Center, University of Vermont, Burlington.
authors.forename: Donald L
authors.initials: DL
authors.lastname: Weaver
mesh_terms: D000328:Adult; D001706:Biopsy; D001940:Breast / Q000473:pathology*; D001943:Breast Neoplasms / Q000473:pathology*; D018270:Carcinoma, Ductal, Breast / Q000473:pathology; D002285:Carcinoma, Intraductal, Noninfiltrating / Q000473:pathology; D003951:Diagnostic Errors; D005260:Female; D006801:Humans; D008875:Middle Aged; D009361:Neoplasm Invasiveness / Q000473:pathology; D015588:Observer Variation; D010338:Pathology, Clinical / Q000592:standards