Abstract
Objective
Histopathological diagnosis of thymic epithelial tumors according to the current World Health Organization classification is not adequately reproducible; however, most thoracic clinicians are unaware of this. We illustrate this problem in practical settings to raise clinician awareness.
Methods
An expert pathologist specialized in thymic pathology and a trained general pathologist independently diagnosed 158 resected thymic epithelial tumors. Assuming that the expert’s diagnoses were more accurate, the two pathologists’ diagnoses were judged to be concordant when tumor subtypes (thymoma) or categories (thymic carcinoma and neuroendocrine tumor) were in agreement.
Results
The concordance rates for different thymoma subtypes were 75 % (3/4), 30 % (11/37), 100 % (17/17), 80 % (39/49), and 53 % (9/17) for types A, AB, B1, B2, and B3, respectively. Discordant cases of type AB thymoma were mainly diagnosed as type B1 or B2 by the general pathologist. Discordant cases of type B2 thymoma were diagnosed as type AB, B1, or B3, and discordant cases of type B3 thymoma were diagnosed as type A, B2, or carcinoma. Discordant cases of thymic carcinoma were diagnosed as type A or B3 thymoma.
Conclusion
Investigation of the concordant and discordant cases suggested that reasonable discrepancies can occur because of the noncommittal categorical boundaries inherent in this classification. Thoracic clinicians should consider this potential problem in daily practice.
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References
Rosai J, Sobin L. Histological typing of tumours of the thymus. In: Rosai J, Sobin L, editors. World Health Organization, international histological classification of tumours. Berlin: Springer; 1999. p. 9–14.
Müller-Hermelink HK, Engel P, Kuo TT, Ströbel P, Marx A, Harris NL, et al. Tumors of the thymus: introduction. In: Travis WD, Brambilla E, Müller-Hermelink HK, Harris CC, editors. Pathology and genetics of tumours of the lung, pleura, thymus and heart (World Health Classification of tumours). Lyon: IARC Press; 2004. p. 148–51.
Verghese ET, den Bakker MA, Campbell A, Hussein A, Nicholson AG, Rice A, et al. Interobserver variation in the classification of thymic tumours—a multicentre study using the WHO classification system. Histopathology. 2008;53:218–23.
Rieker RJ, Hoegel J, Morresi-Hauf A, Hofmann WJ, Blaeker H, Penzel R, et al. Histologic classification of thymic epithelial tumors: comparison of established classification schemes. Int J Cancer. 2002;98:900–6.
Chen G, Marx A, Chen WH, Yong J, Puppe B, Stroebel P, et al. New WHO histologic classification predicts prognosis of thymic epithelial tumors: a clinicopathologic study of 200 thymoma cases from China. Cancer. 2002;95:420–9.
Park MS, Chung KY, Kim KD, Yang WI, Chung JH, Kim YS, et al. Prognosis of thymic epithelial tumors according to the new World Health Organization histologic classification. Ann Thorac Surg. 2004;78:992–7.
Shimosato Y. Controversies surrounding the subclassification of thymoma. Cancer. 1994;74:542–4.
Bernatz PE, Harrison EG, Clagett OT. Thymoma: a clinicopathologic study. J Thorac Cardiovasc Surg. 1961;42:424–44.
Müller-Hermelink HK, Marino M, Palestro G, Schumacher U, Kirchner T. Immunohistological evidences of cortical and medullary differentiation in thymoma. Virchows Arch (Pathol Anat). 1985;408:143–61.
Müller-Hermelink HK, Marino M, Palestro G. Pathology of thymic epithelial tumors. Curr Top Pathol. 1986;75:207–68.
Suster S, Moran CA. Primary thymic epithelial neoplasms: spectrum of differentiation and histological features. Semin Diagnost Pathol. 1999;16:2–17.
Suster S, Moran CA. Thymoma classification. The ride of the valkyries? Am J Clin Pathol. 1999;112:308–10.
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.
Suster S, Moran CA. Problem areas and inconsistencies in the WHO classification of thymoma. Semin Diagn Pathol. 2005;22:188–97.
Suster S, Moran CA. Thymoma classification: current status and future trends. Am J Clin Pathol. 2006;125:542–54.
Detterbeck FC. Clinical value of the WHO classification system of thymoma. Ann Thorac Surg. 2006;81:2328–34.
Close PM, Kirchner T, Uys CJ, Müller-Hermelink HK. Reproducibility of a histogenetic classification of thymic epithelial tumours. Histopathology. 1995;26:339–43.
Dawson A, Ibrahim NB, Gibbs AR. Observer variation in the histopathological classification of thymoma: correlation with prognosis. J Clin Pathol. 1994;47:519–23.
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.
Müller-Hermelink HK, Mukai K, Sng I, Palestro G, Zettl A, Molina TJ, et al. Type B3 thymoma. In: Travis WD, Brambilla E, Müller-Hermelink HK, Harris CC, editors. Pathology and genetics of tumours of the lung, pleura, thymus and heart (World Health Classification of tumours). Lyon: IARC Press; 2004. p. 164–6.
Müller-Hermelink HK, Sng I, Palestro G, Molina TJ, Laeng RH, Harris NL, et al. Type B2 thymoma. In: Travis WD, Brambilla E, Müller-Hermelink HK, Harris CC, editors. Pathology and genetics of tumours of the lung, pleura, thymus and heart (World Health Classification of tumours). Lyon: IARC Press; 2004. p. 161–3.
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Sakakura, N., Tateyama, H., Nakamura, S. et al. Diagnostic reproducibility of thymic epithelial tumors using the World Health Organization classification: note for thoracic clinicians. Gen Thorac Cardiovasc Surg 61, 89–95 (2013). https://doi.org/10.1007/s11748-012-0187-z
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DOI: https://doi.org/10.1007/s11748-012-0187-z