Review ArticlesThe Genitourinary Pathology Society Update on Classification and Grading of Flat and Papillary Urothelial Neoplasia With New Reporting Recommendations and Approach to Lesions With Mixed and Early Patterns of NeoplasiaAmin, Mahul B. MD*,†; Comperat, Eva MD‡,§; Epstein, Jonathan I. MD∥,¶,#; True, Lawrence D. MD**; Hansel, Donna MD, PhD††; Paner, Gladell P. MD‡‡; Al-Ahmadie, Hikmat MD§§,∥∥; Baydar, Dilek MD¶¶; Bivalacqua, Trinity MD¶; Brimo, Fadi MD##; Cheng, Liang MD***; Cheville, John MD†††; Dalbagni, Guido MD‡‡‡; Falzarano, Sara MD§§§; Gordetsky, Jennifer MD∥∥∥; Guo, Charles C. MD¶¶¶; Gupta, Sounak MD†††; Hes, Ondra MD, PhD###; Iyer, Gopa MD****; Kaushal, Seema MD††††; Kunju, Lakshmi MD‡‡‡‡; Magi-Galluzzi, Cristina MD, PhD§§§§; Matoso, Andres MD∥,¶,#; Netto, George MD§§§§; Osunkoya, Adeboye O. MD∥∥∥∥,¶¶¶¶; Pan, Chin Chen MD####; Pivovarcikova, Kristina MD###; Raspollini, Maria R. MD*****; Reis, Henning MD†††††; Rosenberg, Jonathan MD****; Roupret, Morgan MD‡‡‡‡‡; Shah, Rajal B. MD§§§§§,∥∥∥∥∥; Shariat, Shahrokh MD¶¶¶¶¶,#####; Trpkov, Kiril MD******; Weyerer, Veronika MD††††††; Zhou, Ming MD, PhD‡‡‡‡‡‡; McKenney, Jesse MD§§§§§§; Reuter, Victor E. MD§§Author Information *Department of Pathology and Laboratory Medicine, University of Tennessee Health Science, Memphis ∥∥∥Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, TN †Department of Urology, Keck School of Medicine of University of Southern California, Los Angeles, CA ‡Department of Pathology, Vienna General Hospital ¶¶¶¶¶Department of Urology, Comprehensive Cancer Center, Medical University Vienna, Vienna General Hospital, Vienna, Austria §Medical University Department of Pathology, Hôpital Tenon, Sorbonne University ‡‡‡‡‡GRC 5 Predictive ONCO-URO, AP-HP, Urology, Pitie-Salpetriere Hospital, Sorbonne University, Paris, France Departments of ∥Pathology ¶Urology #Oncology, The Johns Hopkins Medical Institutions, Baltimore, MD **Department of Pathology, University of Washington School of Medicine, Seattle, WA ††Department of Pathology, Oregon Health Science University, OR ‡‡Department of Pathology, University of Chicago, Chicago, IL Departments of §§Pathology ‡‡‡Urology ****Medicine ∥∥Urology Service, Department of Surgery, Memorial Sloan Kettering Cancer Center, New York, NY ¶¶Department of Pathology, Koc University School of Medicine, Istanbul, Turkey ##Department of Pathology, Montreal, QC ******Department of Pathology and Laboratory Medicine, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada ***Department of Pathology and Laboratory Medicine, Indiana University School of Medicine, Indianapolis, IN †††Department of Pathology, Mayo Clinic, Rochester, MN §§§Department of Pathology, Immunology and Laboratory Medicine, University of Florida, Gainesville, FL ¶¶¶Department of Pathology, The University of Texas MD Anderson Cancer Center Departments of §§§§§Pathology ∥∥∥∥∥Urology, Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, TX ###Department of Pathology, Charles University in Prague, Faculty of Medicine and University Hospital in Plzen, Plzen, Czech Republic ††††Department of Pathology, All India Institute of Medical Sciences, New Delhi, Delhi, India ‡‡‡‡Department of Pathology, Michigan Medicine, University of Michigan, Ann Arbor, MI §§§§Department of Pathology, The University of Alabama at Birmingham, Birmingham, AL Departments of ∥∥∥∥Pathology and Laboratory Medicine ¶¶¶¶Urology, Emory University School of Medicine, Atlanta, GA ####Department of Pathology, Taipei Veterans General Hospital, Taipei, Taiwan *****Department of Histopathology and Molecular Diagnostics, University Hospital Careggi, Florence, Italy †††††Institute of Pathology, University Medicine Essen, University of Duisburg-Essen, Essen ††††††Department of Pathology, University of Erlangen-Nuremberg, Erlangen, Germany #####Institute for Urology and Reproductive Health, I.M. Sechenov First Moscow State Medical University, Moscow, Russia ‡‡‡‡‡‡Department of Pathology, Tufts Medical Center, Boston, MA §§§§§§Robert J Tomsich Pathology and Laboratory Medicine Institute, Cleveland Clinic, Cleveland, OH M.B.A., E.C., and J.I.E. are co-first authors. The authors have no funding or conflicts of interests to disclose relevant to this work. Reprints: Mahul B. Amin, MD, Department of Pathology and Laboratory Medicine, University of Tennessee Health Science Center, 930 Madison Avenue, Suite 531, Memphis, TN 38163 (e-mail: [email protected]). All figures can be viewed online in color at www.anatomicpathology.com. Advances In Anatomic Pathology: July 2021 - Volume 28 - Issue 4 - p 179-195 doi: 10.1097/PAP.0000000000000308 Buy Metrics Abstract The Genitourinary Pathology Society (GUPS) undertook a critical review of the recent advances in bladder neoplasia with a focus on issues relevant to the practicing surgical pathologist for the understanding and effective reporting of bladder cancer, emphasizing particularly on the newly accumulated evidence post-2016 World Health Organization (WHO) classification. The work is presented in 2 manuscripts. Here, in the first, we revisit the nomenclature and classification system used for grading flat and papillary urothelial lesions centering on clinical relevance, and on dilemmas related to application in routine reporting. As patients of noninvasive bladder cancer frequently undergo cystoscopy and biopsy in their typically prolonged clinical course and for surveillance of disease, we discuss morphologies presented in these scenarios which may not have readily applicable diagnostic terms in the WHO classification. The topic of inverted patterns in urothelial neoplasia, particularly when prominent or exclusive, and beyond inverted papilloma has not been addressed formally in the WHO classification. Herein we provide a through review and suggest guidelines for when and how to report such lesions. In promulgating these GUPS recommendations, we aim to provide clarity on the clinical application of these not so uncommon diagnostically challenging situations encountered in routine practice, while also importantly advocating consistent terminology which would inform future work. Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.