Thymic epithelial malignancies are rare tumors. There have been many obstacles to progress in these diseases. Among these has been the lack of an official, consistent stage classification system put forth by the American Joint Committee on Cancer (AJCC) and the Union for International Cancer Control (UICC) —the bodies responsible for defining stage classification throughout the world. At least 15 different stage classification systems have been proposed and used.¹ x 1 Filosso, P, Ruffini, E, Lausi, P, Lucchi, M, Oliaro, A, and Detterbeck, F. Historical perspectives: the evolution of the thymic epithelial tumors staging system. Lung Cancer. 2014; 83: 126–132 Abstract | Full Text | Full Text PDF | PubMed | Scopus (27) | Google Scholar See all References These have been largely empirically derived, based on data from small numbers of patients. Perhaps the most widely used have been the Masaoka classification (derived from data on 91 patients),² x 2 Masaoka, A, Monden, Y, Nakahara, K, and Tanioka, T. Follow-up study of thymomas with special reference to their clinical stages. Cancer. 1981; 48: 2485–2492 Crossref | PubMed | Scopus (1191) | Google Scholar See all References and the Koga modification of this (based on 76 patients).³ x 3 Koga, K, Matsuno, Y, Noguchi, M et al. A review of 79 thymomas: modification of staging system and reappraisal of conventional division into invasive and non-invasive thymoma. Pathol Int. 1994; 44: 359–367 Crossref | PubMed | Scopus (211) | Google Scholar See all References Even among centers using one of these classification systems, often the definitions have been interpreted differently because of vague wording, thus hampering the ability to collaborate effectively.⁴ x 4 Detterbeck, FC, Moran, C, Huang, J et al. Which way is up? Policies and procedures for surgeons and pathologists regarding resection specimens of thymic malignancy. J Thorac Oncol. 2011; 6: S1730–S1738 Abstract | Full Text | Full Text PDF | PubMed | Scopus (63) | Google Scholar See all References

Malignant pleural mesothelioma (MPM) is an uncommon and usually fatal malignancy. A well-validated and internationally accepted staging system is essential to evaluate new therapies for this difficult disease. Until the mid 1990s no such staging system existed. At least six staging paradigms had been proposed, none evidence-based, and few using a TNM (tumor, node, metastasis) system. In 1994, at a workshop sponsored by the International Association for the Study of Lung Cancer (IASLC) and the International Mesothelioma Interest Group (IMIG) MPM investigators analyzed existing surgical databases to develop a TNM-based staging system.¹ x 1 Rusch, VW. A proposed new international TNM staging system for malignant pleural mesothelioma. From the International Mesothelioma Interest Group. Chest. 1995; 108: 1122–1128 Crossref | PubMed | Scopus (473) | Google Scholar See all References Subsequently, this proposed staging system was accepted by the UICC (International Union Against Cancer) and the AJCC (American Joint Commission on Cancer) as the international MPM staging system for the 6th and 7th editions of their staging manuals.² x 2 International Union Against Cancer. TNM Classification of Malignant Tumours. 7th Ed. United Kingdom Wiley-Blackwell, Oxford; 2009 Google Scholar See all References ,³ x 3 American Joint Committee on Cancer. AJCC Cancer Staging Manual. 7th Ed. New York, NY Springer; 2010 Crossref | Google Scholar See all References The IMIG staging system has since been widely used in both retrospective analyses and prospective clinical trials. However, widespread concerns exist about the validity of the current MPM staging system because it is derived from analyses of small, retrospective surgical series, can be difficult to apply to clinical staging, and uses descriptors for lymph node involvement, which may not be relevant to MPM. Therefore, in collaboration with IMIG, the IASLC has decided to update the staging system for MPM by developing a large international database, an effort modeled on the revisions that the IASLC proposed for lung cancer staging for the 7th editions of the UICC and AJCC manuals.⁴ x 4 Goldstraw, P, Crowley, J, Chansky, K..., and International Association for the Study of Lung Cancer International Staging Committee. Participating Institutions. The IASLC Lung Cancer Staging Project: proposals for the revision of the TNM stage groupings in the forthcoming (seventh) edition of the TNM Classification of malignant tumours. J Thorac Oncol. 2007; 2: 706–714 Abstract | Full Text | Full Text PDF | PubMed | Scopus (2141) | Google Scholar See all References Here we report the initial analyses of the international IASLC/IMIG database for MPM, with the primary aim to identify areas in which the current staging system warrants modification.