The International Collaboration on Cancer Reporting is a quadripartite alliance formed by the Royal College of Pathologists of Australasia, the Royal College of Pathologists of the United Kingdom, the College of American Pathologists, and the Canadian Partnership Against Cancer. The International Collaboration on Cancer Reporting was formed with a view to reducing the global burden of cancer data set development and reduplication of the effort by different international institutions that commission, publish, and maintain standardized cancer-reporting data sets. The resultant standardization of cancer reporting would be expected to benefit not only those countries directly involved in the collaboration, but also others not in a position to develop their own data sets. The main objective of the International Collaboration on Cancer Reporting is to develop an evidence-based-reporting data set for each cancer site, and to this end, a project to develop data sets for prostate, endometrium, and lung cancers and malignant melanoma was piloted by the quadripartite group. This review describes the process of development of the endometrial cancer data set.