Richard N Mitchell, MD, PhD, Lawrence J. Henderson Professor of Pathology and Health Sciences and Technology, Department of Pathology, Harvard Medical School, Staff Pathologist, Brigham and Women's Hospital, Boston, Massachusetts Vinay Kumar, MBBS, MD, FRCPath, Alice Hogge and Arthur A. Baer Distinguished Service Professor of Pathology, Biologic Sciences Division and the Pritzker Medical School, The University of Chicago, Chicago, Illinois, USA Abul K. Abbas, MBBS, Distinguished Professor and Chair, Department of Pathology, University of California San Francisco, San Francisco, California Jon C. Aster, MD, PhD, Professor of Pathology, Harvard Medical School; Brigham and Women's Hospital, Boston, Massachusetts