On behalf of the ESTS Thymic Working Group, emails were sent to ESTS members to ask for participation on this retrospective data collection in the treatment of patients with TETs with pleural involvement. Respondents received a detailed standardized questionnaire (Supplementary Material, Table S1). In this collaborative effort, a total of 152 patients with pleural disease of TETs were reported by 12 institutions from 8 countries. All institutions were specialized thoracic surgery centres routinely performing surgery on patients with TETs. The reported patients were diagnosed and operated between February 1977 and November 2014 (90% of patients between 1 January 2001 and 30 November 2014, Supplementary Material, Table S2).