The foundation of pathology is the visual interpretation of microscopic slides. Essential components of the reporting include tumor classification and assessment of grade, stage and other prognostic parameters. Although strict criteria have been elaborated by professional organizations such as ISUP, there is invevitably an element of subjectivity. This reference image database attempts to standardize reporting by letting leading international experts review images independently. When a case has reached consensus defined by a certain percentage of agreement, it is made available to all members of ISUP. A sample of cases will later be made public.