Thymic malignancies present particular issues due to the pace of disease progression, patterns of recurrence, and causes of death that make nuances of how outcomes are reported particularly important. The relatively limited number of patients also creates a challenge to glean as much as possible from the available experience, but risks over-interpretation and potentially misleading conclusions. Therefore the International Thymic Malignancy Interest Group has developed a set of standards for reporting of outcome measures of clinical studies, which have been adopted for collaborative projects undertaken by the organization. Widespread adoption of this baseline will enhance the ability to compare results from different series.