Thymic Epithelial Tumors: Pathological Classification, Prognosis and Tumor Staging


  • Peerayut Sitthichaiyakul Department of Pathology, Faculty of Medicine, Naresuan University


thymoma, thymic carcinoma, thymic epithelial tumor, pathologic classification, prognosis, staging


Thymic epithelial tumors (TETs) including thymoma and thymic carcinoma, are the most common primary anterior mediastinal tumors. They are approximately 17-50% of anterior mediastinal mass detected in patients. The incidence rate of TETs ranges from 1.5 up to 4.9/ million/year. These tumors are infrequent and having indolent growth. Therefore, the studies for accurate biologic features, prognosis and clinical course of the TETs are still limited. Histopathologic features of the tumors are important factors for evaluating the biologic features of TETs. Clinical staging is also an important prognostic factor for the tumors. Complete surgical resection is the treatment of choice for tumors in the early stages. Chemotherapy and radiotherapy are considered for selected patients. Currently, at least 24 histopathologic classifications and 14 staging systems have been proposed. The widely accepted histopathologic classifications and clinical staging systems are summarized and compared in this article. Prognostic factors for TETs are reviewed. Histopathologic patterns, immunohistochemical staining features of the majority of TETs, and guidelines for pathological examination are also summarized to guide accurate pathological diagnosis and tumor staging.


Hasserjian RP, StrÖbel P, Marx A. Pathology of thymic tumors. Semin Thorac Cardiovasc Surg 2005; 17:2-11.

Roden AC. Evolution of Classification of Thymic Epithelial Tumors in the Era of Dr Thomas V. Colby. Arch Pathol Lab Med 2017;141:232-46.

Kondo K, Yoshizawa K, Tsuyuguchi M, Kimura S, Sumitomo M, Morita J, et al. WHO histologic classification is a prognostic indicator in thymoma. Ann Thorac Surg 2004;77:1183-8.

Forquer JA. Thymic Neoplasms. Curr Probl Cancer 2010;34:328-66.

Scorsetti M, Leo F, Trama A, D'Angelillo, Serpico D, Macerelli M, et al. Crit Rev Oncol Hematol 2016;99:332-50.

Berardi R, De Lisa M, Pagliaretta S, Onofri A, Morgese F, Savini A, et al. Thymic neoplasms: an update on the use of chemotherapy and new targeted therapies. A literature review. Cancer Treat Rev 2014; 40:495-506.

Moran CA, Walsh G, Suster S, Kaiser L. Thymomas II: a clinicopathologic correlation of 250 cases with a proposed staging system with emphasis on pathologic assessment. Am J Clin Pathol 2012;137:451-61.

Mikhail M, Mekhail Y, Mekhail T. Thymic neoplasms: a clinical update. Curr Oncol Rep 2012;14:350-8.

Weis CA, Yao X, Deng y, Detterbeck FC, Marino M, Nicholson AG, et al. The Impact of Thymoma Histotype on Prognosis in a Worldwide Database. J Thorac Oncol 2015;10:367-72.

Lamarca A, Moreno V, Feliu J. Thymoma and thymic carcinoma in the target therapies era. Cancer Treat Rev 2013;39:413-20.

Thomas de Montpréville V, Ghigna MR, Lacroix L, Besse B, Broet P, Dartevelle P, et al. Thymic carcinomas: clinicopathologic study of 37 cases from a single institution. Virchows Arch 2013;462:307-13.

Wright CD. Management of thymomas. Crit Rev Oncol Hematol 2008;65:109-20.

Carter BW, Marom EM, Detterbeck FC. Approaching the patient with an anterior mediastinal mass: a guide for clinicians. J Thorac Oncol 2014;9:S102-9.

Weissferdt A, Kalhor N, Bishop JA, Jang SJ, Ro J, Petersson F, et al. THYMOMA: A clinicopathological correlation of 1470 cases. Hum Pathol 2018;73:7-15.

Marchevsky A, Marx A, StrÖbel P, Suster S, Venuta F, Marino M, et al. Policies and reporting guidelines for small biopsy specimens of mediastinal masses. J Thorac Oncol 2011;6:S1724-9.

Weydert JA, de Young BR, Leslie KO; Association of Directors of Anatomic and Surgical Pathology. Recommendations for the reporting of surgically resected thymic epithelial tumors. Human Pathol 2009;40:


Moran CA, Weissferdt A, Kalhor N, Solis LM, Behrens C, Wistuba II, et al. Thymomas I: a clinicopathologic correlation of 250 cases with emphasis on the World Health Organization schema. Am J Clin Pathol 2012;137:444-50.

Suster S, Moran CA. Problems in the classification of thymoma. Diagnostic Histopathology 2010;16:221-7.

Suster S, Moran CA. Thymoma, atypical thymoma, and thymic carcinoma: a novel conceptual approach to the classification of thymic epithelial neoplasms. Am J Clin Pathol 1999;111:826-33.

Moran CA, Suster S. The World Health Organization (WHO) histologic classification of thymomas: a reanalysis. Curr Treat Options Oncol 2008;9:288-99.

Detterbeck FC. Clinical value of the WHO classification system of thymoma. Ann Thorac Surg 2006;81:2328-34.

Marx A, Chan JKC, Coindre JM, Detterbeck F, Girard N, Harris NL, et al. The 2015 World Health Organization Classification of Tumors of the Thymus: Continuity and Changes. J Thorac Oncol 2015;10:1383-95.

Marx A, StrÖbel P, Badve SS, Chalabreysse L, Chan JKC, Chen G, et al. ITMIG Consensus Statement on the Use of the WHO Histological Classification of Thymoma and Thymic Carcinoma: Refined Definitions, Histological Criteria, and Reporting. J Thorac Oncol 2014;9:596-611.

Den Bakker MA, Roden AC, Marx A, Marino M. Histologic Classification of Thymoma: A Practical Guide for Routine Cases. J Thorac Oncol 2014;9:s125-30.

Zucali PA, Di Tommaso L, Petrini I, Battistaa S, Lee HS, Merino M, et al. Reproducibility of the WHO classification of thymomas: Practical implications. Lung Cancer 2013;79:236-41.

StrÖbel P, Hohenberger P, Marx A. Thymoma and Thymic Carcinoma: Molecular Pathology and Targeted Therapy. J Thorac Oncol 2010;5:s286-90.

Thomas de Montpréville V, Quilhot P, Chalabreysse L, De Muret A, Hofman V, Lantuéjoul S, et al. Glut-1 intensity and pattern of expression in thymic epithelial tumors are predictive of WHO subtypes. Pathol Res Pract 2015;211:996-1002.

Du MJ, Shen Q, Yin H, Rao Q, Zhou MX. Diagnostic roles of MUC1 and GLUT1 in differentiating thymic carcino29. StrÖbel P, Hohenberger P, Marx A. Thymoma and Thymic Carcinoma: Molecular Pathology and Targeted Therapy. J Thorac Oncol 2010;5:s286-90.

Falkson CB, Bezjak A, Darling G, Gregg R, Malthaner R, Maziak DE, et al. The management of thymoma: a systematic review and practice guideline. J Thorac Oncol 2009;4:911-9.

Roden AC, Yi ES, Jenkins SM, Edwards KK, Donovan JL, Cassivi SD, et al. Modified Masaoka Stage and Size Are Independent Prognostic Predictors in Thymoma and Modified Masaoka Stage Is Superior to Histopathologic Classifications. J Thorac Oncol 2015;10:691-700.

Detterbeck F, Youssef S, Ruffini E, Okumura M. A review of prognostic factors in thymic malignancies. J Thorac Oncol 2011;6:S1698-704.

Margaritora S, Cesario A, Cusumano G, Meacci E, D'Angelillo R, Bonassi S, et al. Thirty-five-year followup analysis of clinical and pathologic outcomes of thymoma surgery. Ann Thorac Surg 2010;89:245-52.

Jain RK, Mehta RJ, Henley JD, Kesler KA, Loehrer PJ, Badve S. WHO types A and AB thymomas: not always benign. Mod Pathol 2010;23:1641-9.

Safieddine N, Liu G, Cuningham K, Ming T, Hwang D, Brade A, et al. Prognostic factors for cure, recurrence and long-term survival after surgical resection of thymoma. J Thorac Oncol 2014;9:1018-22.

Nicholson AG, Detterbeck FC, Marino M, Kim J, Stratton K, Giroux D, et al. The IASLC/ITMIG Thymic Epithelial Tumors Staging Project: Proposals for the T component for the Forthcoming (8th) Edition of the TNM Classification of Malignant Tumors. J Thorac Oncol 2014;9:s73-80.

Detterbeck FC, Stratton K, Giroux D, Asamura H, Crowley J, Falkson C, et al. The IASLC/ITMIG Thymic Epithelial Tumors Staging Project: Proposal for an Evidence-Based Stage Classification System for the Forthcoming (8th) Edition of the TNM Classification of Malignant Tumors. J Thorac Oncol 2014;9:s65-72.

Marchevsky AM, Gupta R, Casadio C, Hiroshima K, Jambhekar NA, Kim DJ, et al. World Health Organization classification of thymomas provides significant prognostic information for selected stage III patients: evidence from an international thymoma study group. Hum Pathol 2010;41:1413-21.

Marchevsky AM, Gupta, R, McKenna, RJ, Wick M, Moran C, Zakowski MF, et al. Evidence-based pathology and the pathologic evaluation of thymomas: The world health organization classification can be simplified into only 3 categories other than thymic carcinoma. Cancer 2008;112:2780-8.

Fukui T, Yokoi K. The new classifications for thymic epithelial tumors: benefits and problems. J Thorac Dis 2017;9:4165-8.

Weksler B, Holden A, Sullivan JL. Impact of Positive Nodal Metastases in Patients with Thymic Carcinoma and Thymic Neuroendocrine Tumors. J Thorac Oncol 2015;10:1642-7.

Bhora FY, Chen DJ, Detterbeck FC, Asamura H, Falkson C, Filosso PL, et al. The ITMIG/IASLC Thymic Epithelial Tumors Staging Project: A Proposed Lymph Node Map for Thymic Epithelial Tumors in the Forthcoming 8th Edition of the TNM Classification of Malignant Tumors. J Thorac Oncol 2014;9:S88-96.

Ried M, Eicher M-M, Neu R, Sziklavari Z, Hofmann H-S. Evaluation of the new TNM-staging system for thymic malignancies: impact on indication and survival. World J Surg Oncol 2017;15:214.

Weksler B, Pennathur A, Sullivan JL, Nason KS. Resection of thymoma should include nodal sampling. J Thorac Cardiovasc Surg 2015;149:737-42.

Gao L, Wang C, Fang W, Zhang J, Lv C, Fu S. Outcome of multimodality treatment for 188 cases of type B3 thymoma. J Thorac Oncol 2013;8:1329-34.

Leisibach P, Schneiter D, Soltermann A, Yamada Y, Weder W, Jungraithmayr W. Prognostic value of immunohistochemical markers in malignant thymic epithelial tumors. J Thorac Dis 2016;8:2580-91.

Masaoka A. Staging System of Thymoma. J Thorac Oncol 2010;5:s304-12.

Detterbeck FC, Nicholson AG, Kondo K, Schil PV, Moran C. The Masaoka-Koga Stage Classification for Thymic Malignancies: Clarification and Definition of Terms. J Thorac Oncol 2011;6:s1710-6.

Weissferdt A, Moran CA. Staging of thymic epithelial neoplasms: Thymoma and thymic carcinoma. Pathol Res Pract 2015;211:2-11.

Detterbeck FC, Moran C, Huang J, Suster S, Walsh G, Kasiser L, et al. Which Way is Up? Policies and Procedures for Surgeons and Pathologists Regarding Resection Specimens of Thymic Malignancy. J Thorac Oncol 2011;6:s1730-8.

Kondo K, Van Schil P, Detterbeck FC, Okumura M, Stratton K, Giroux D, et al. The IASLC/ITMIG Thymic Epithelial Tumors Staging Project: Proposals for the N and M Components for the Forthcoming (8th) Edition

of the TNM Classification of Malignant Tumors. J Thorac Oncol 2014;9:s81-7.

Hwang Y, Park IK, Park S, Kim ER, Kang CH, Kim YT. Lymph Node Dissection in Thymic Malignancies: Implication of the ITMIG Lymph Node Map, TNM Stage Classification, and Recommendations. J Thorac Oncol 2016;11:108-14.

Koppitz H, Rockstroh JK, Schüller H, Standop J, Skowasch D, Müller-Hermelink HK. et al. State-ofthe-art classification and multimodality treatment of malignant thymoma. Cancer Treat Rev 2012;38:540-8.






Review Articles