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J Thorac Oncol. 2014 May;9(5):596-611. doi: 10.1097/JTO.0000000000000154.

ITMIG consensus statement on the use of the WHO histological classification of thymoma and thymic carcinoma: refined definitions, histological criteria, and reporting.

Author information

1
*Institute of Pathology, University Medical Centre Mannheim, University of Heidelberg, Mannheim, Germany; †Institute of Pathology, University of Göttingen, Göttingen, Germany; ‡Department of Pathology, Indiana University Health Pathology Laboratory, Indianapolis, Indiana; §Department of Pathology, Louis Pradel Hospital, Hospices Civils de Lyon, Lyon, France; ‖Department of Pathology, Queen Elizabeth Hospital, Hong Kong, China; ¶Department of Pathology, Shanghai Pulmonary Hospital and Tongji University School of Medicine, Shanghai, China; #University Institute of Pathology, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland; **Department of Thoracic Surgery, Yale University School of Medicine, New Haven, Connecticut; ††Department of Respiratory Medicine, Louis Pradel Hospital, Hospices Civils de Lyon, Lyon, France; ‡‡Department of Surgery, Memorial Sloan-Kettering Cancer Center, New York, New York; §§Division of Pathology, Zurich, Switzerland; ‖‖Department of Pathology, Catholic University, Rome, Italy; ¶¶Department of Pathology, Regina Elena National Cancer Institute, Rome, Italy; ##Department of Diagnostic Pathology, Hokkaido University Hospital, Sapporo, Japan; ***Department of Pathology, AP-HP, Necker, University Paris Descartes, Paris, France; †††Department of Diagnostic Pathology, Saiseikai Central Hospital, Tokyo, Japan; ‡‡‡Diagnostic Thoracic Pathology, Royal Brompton Hospital, and Imperial College London, London, United Kingdom; §§§Department of Histopathology, The Cristie Hospital, and Institute of Cancer Sciences, The University of Manchester, Manchester, United Kingdom; ‖‖‖Institute of Pathology, University of Erlangen, Erlangen, Germany; ¶¶¶Centro Diagnostico Italiano, Milano, Italy; ###Department of Thoracic Surgery, University of Torino, Torino, Italy; and ****Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York, New York.

Abstract

INTRODUCTION:

The 2004 version of the World Health Organization classification subdivides thymic epithelial tumors into A, AB, B1, B2, and B3 (and rare other) thymomas and thymic carcinomas (TC). Due to a morphological continuum between some thymoma subtypes and some morphological overlap between thymomas and TC, a variable proportion of cases may pose problems in classification, contributing to the poor interobserver reproducibility in some studies.

METHODS:

To overcome this problem, hematoxylin-eosin-stained and immunohistochemically processed sections of prototypic, "borderland," and "combined" thymomas and TC (n = 72) were studied by 18 pathologists at an international consensus slide workshop supported by the International Thymic Malignancy Interest Group.

RESULTS:

Consensus was achieved on refined criteria for decision making at the A/AB borderland, the distinction between B1, B2, and B3 thymomas and the separation of B3 thymomas from TCs. "Atypical type A thymoma" is tentatively proposed as a new type A thymoma variant. New reporting strategies for tumors with more than one histological pattern are proposed.

CONCLUSION:

These guidelines can set the stage for reproducibility studies and the design of a clinically meaningful grading system for thymic epithelial tumors.

PMID:
24722150
DOI:
10.1097/JTO.0000000000000154
[Indexed for MEDLINE]
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