Original ArticlesReproducibility of AJCC Criteria for Classifying Deeply Invasive Colon Cancers Is Suboptimal for Consistent Cancer StagingPanarelli, Nicole C. MD*; Hammer, Suntrea T.G. MD†; Lin, Jingmei MD, PhD‡; Gopal, Purva MD†; Nalbantoglu, ILKe MD§; Zhou, Lili PhD∥; Cheng, Jerome MD∥; Gersten, Adam J. MD*; McHugh, Jonathan B. MD∥; Parkash, Vinita MBBS, MPH§; Lucas, Elena MD†; Westerhoff, Maria MD∥Author Information *Albert Einstein College of Medicine, Bronx, NY †University of Texas Southwestern Medical Center, Dallas, TX ‡Indiana University School of Medicine, Indianapolis, IN §Yale University School of Medicine, New Haven, CT ∥University of Michigan Medical School, Ann Arbor, MI Conflicts of Interest and Source of Funding: The authors have disclosed that they have no significant relationships with, or financial interest in, any commercial companies pertaining to this article. Correspondence: Nicole C. Panarelli, MD, Department of Pathology, Albert Einstein College of Medicine, Montefiore Medical Center, 111 East 210 Street, Central 428, Bronx, NY 10467 (e-mail: [email protected]). The American Journal of Surgical Pathology: October 2020 - Volume 44 - Issue 10 - p 1381-1388 doi: 10.1097/PAS.0000000000001510 Buy Metrics Abstract The eighth edition of the American Joint Committee on Cancer (AJCC) Staging Manual attempts to address ambiguity in the pT category assignment for colon cancer from prior editions. Despite modifications, the distinction between the pT3 and pT4a categories continues to be a source of diagnostic confusion. In this study, we assessed interobserver agreement among pathologists from different institutions in the application of AJCC eighth edition criteria for categorizing deeply invasive colonic adenocarcinomas. We identified morphologic patterns that produce diagnostic confusion. We assessed 47 colon cancers that closely approached the serosal surface. Six pathologists with interest in gastrointestinal pathology and 4 focused in other subspecialties classified each case as pT3 or pT4a, based on examination of low-magnification and high-magnification images of the most deeply invasive area. Interobserver agreement was assessed using Fleiss’ κ. Cases displayed 3 morphologic patterns at the advancing tumor edge, namely, (1) continuous invasion through an inflammatory focus, (2) pushing border, and (3) infiltrative glands and cell clusters with serosal reaction. Gastrointestinal pathologists achieved slight (κ=0.21) or moderate (κ=0.46) and (κ=0.51) agreement in each category, whereas agreement among nongastrointestinal pathologist was fair (0.31) and (0.39), or moderate (0.57) for each category, respectively. In 10 (21%) cases, the distinction between pT3 and pT4a would have changed the overall clinical stage. We conclude that histologic criteria for serosal penetration is a persistent source of diagnostic ambiguity for gastrointestinal and general pathologists in the pT categorization of colon cancers. Clarification of these criteria will help ensure uniform reporting of pathologic and clinical stage. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.