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Year : 2019  |  Volume : 150  |  Issue : 2  |  Page : 110-111

The thymoma tale

Department of Pathology (Cardiovascular & Thoracic Division), Seth GS Medical College, Mumbai 400 012, Maharashtra, India

Date of Submission28-Jan-2019
Date of Web Publication18-Oct-2019

Correspondence Address:
Pradeep Vaideeswar
Department of Pathology (Cardiovascular & Thoracic Division), Seth GS Medical College, Mumbai 400 012, Maharashtra
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijmr.IJMR_155_19

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How to cite this article:
Vaideeswar P. The thymoma tale. Indian J Med Res 2019;150:110-1

How to cite this URL:
Vaideeswar P. The thymoma tale. Indian J Med Res [serial online] 2019 [cited 2020 Nov 25];150:110-1. Available from:

Thymic epithelial tumours form the most important differential diagnosis for anterior mediastinal masses, among which thymomas constitute nearly 50 per cent of these lesions. These are infrequent and possess certain unique characteristics [1]. The thymus plays a central role in the development of self-immunological tolerance by appropriate conditioning of T-cell progenitors that enter the gland. Consequently, thymic pathology (including thymomas) leads to the generation of a variety of autoantibodies. Hence, a significant proportion of patients with thymomas present with features of paraneoplastic syndromes (PNSs) to the extent of exclusion of chest-related symptoms. The most common manifestation is myasthenia gravis, induced by anti-acetylcholine esterase antibodies, identified in close to 95 per cent of patients with available clinical data in a large series of Indian patients published in this issue [2]. It must be borne in mind that there are also other PNSs (including multiorgan autoimmunity), secondary cancers as well as opportunistic infections, which are explained in part by acquired T-cell immunodeficiency [3]. The presence of PNSs, paradoxically, was associated with favourable features [4].

On histology, the thymomas, in general, are seen to be composed of epithelial cells and lymphocytes in varying proportions. However, this seemingly innocuous admixture has led to several classification systems over decades [5]. The classification used currently and in this article by Guleria et al[2] is the WHO 2015[6], which identifies five subtypes (A, AB, B1, B2 and B3) depending on the morphology of the epithelial cells (spindloid cells, epithelioid cells or their combinations) and proportion of lymphocytes. The authors concluded that the thymomas of B2 and AB subtypes were the most common in the Indian population, in contrast to the studies from the Western world. However, in a recent, multi-institutional study of 1470 patients with thymomas from 11 countries, a similar distribution was found [7]. Furthermore, the Indian studies quoted [2] are either clinical (without a thorough histological review) or have been studies of 'mixed bag' of mediastinal tumours. Hence, to have an idea of the actual distribution, there is a need to have multi-institutional collaborations with thymomas in sufficient numbers. It would also be important to follow a protocol [8] for clinicoradiological, gross and histological assessment of such tumours, as there are some studies indicating that even tumour sizes are useful in predicting prognosis [9].

Another feature of thymomas is that the histotypes do not necessarily correlate with the clinical behaviour, prognosis and overall survival, which explains the use of the modified Masaoka-Koga staging system [10]. With time, there would presumably be more robust criteria for prognosis and therapeutic management such as utility of the angiogenesis patterns [11], immunoexpression of programmed death ligand 1[12], molecular profiling [13] and even detection of proteomic signatures [14].

Conflicts of Interest: None.

   References Top

den Bakker MA, Roden AC, Marx A, Marino M. Histologic classification of thymoma: a practical guide for routine cases. J Thorac Oncol 2014; 9 (9 Suppl 2) : S125-30.  Back to cited text no. 1
Guleria P, Parshad R, Malik PS, Ray R, Pandey RM, Jain D. Histotyping of Indian thymomas: A clinicopathologic study from north India. Indian J Med Res 2019; 150 : 153-60.  Back to cited text no. 2
Christopoulos P, Fisch P. Acquired T-cell immunodeficiency in thymoma patients. Crit Rev Immunol 2016; 36 : 315-27.  Back to cited text no. 3
Padda SK, Yao X, Antonicelli A, Riess JW, Shang Y, Shrager JB, et al. Paraneoplastic syndromes and thymic malignancies: An examination of the International Thymic Malignancy Interest Group retrospective database. J Thorac Oncol 2018; 13 : 436-46.  Back to cited text no. 4
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.  Back to cited text no. 5
Travis WD, Brambilla E, Burke AP, Marx A, Nicholson AG, editors. WHO classification of tumours of lung, pleura, thymus and heart. 4th ed. Geneva: WHO Press; 2015.  Back to cited text no. 6
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.  Back to cited text no. 7
Nicholson AG, Detterbeck F, Marx A, Roden AC, Marchevsky AM, Mukai K, et al. Dataset for reporting of thymic epithelial tumours: Recommendations from the International Collaboration on Cancer Reporting (ICCR). Histopathology 2017; 70 : 522-38.  Back to cited text no. 8
Bian D, Zhou F, Yang W, Zhang K, Chen L, Jiang G, et al. Thymoma size significantly affects the survival, metastasis and effectiveness of adjuvant therapies: A population based study. Oncotarget 2018; 9 : 12273-83.  Back to cited text no. 9
Detterbeck FC, Nicholson AG, Kondo K, Van Schil P, Moran C. The Masaoka–Koga stage classification for thymic malignancies: Clarification and definition of terms. J Thorac Oncol 2011; 6 : S1710-6.  Back to cited text no. 10
Pfister F, Hussain H, Belharazem D, Busch S, Simon-Keller K, Becker D, et al. Vascular architecture as a diagnostic marker for differentiation of World Health Organization thymoma subtypes and thymic carcinoma. Histopathology 2017; 70 : 693-703.  Back to cited text no. 11
Duan J, Liu X, Chen H, Sun Y, Liu Y, Bai H, et al. Impact of PD-L1, transforming growth factor-β expression and tumor-infiltrating CD8+ T cells on clinical outcome of patients with advanced thymic epithelial tumors. Thorac Cancer 2018; 9 : 1341-53.  Back to cited text no. 12
Enkner F, Pichlhöfer B, Zaharie AT, Krunic M, Holper TM, Janik S, et al. Molecular profiling of thymoma and thymic carcinoma: Genetic differences and potential novel therapeutic targets. Pathol Oncol Res 2017; 23 : 551-64.  Back to cited text no. 13
Wang L, Branson OE, Shilo K, Hitchcock CL, Freitas MA. Proteomic signatures of thymomas. PLoS One 2016; 11 : e0166494.  Back to cited text no. 14


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