Interobserver variation in the classification of thymic lesions including biopsies and resection specimens in an international digital microscopy panel
Histopathology, vol. 77, pp. 734–741
Abstract
AIMS: Thymic tumours are rare in routine pathology practice. Although the World Health Organization (WHO) classification describes a number of well-defined categories, the classification remains challenging. The aim of this study was to investigate the reproducibility of the WHO classification among a large group of international pathologists with expertise in thymic pathology and by using whole slide imaging to facilitate rapid diagnostic turnover. METHODS AND RESULTS: Three hundred and five tumours, consisting of 90 biopsies and 215 resection specimens, were reviewed with a panel-based virtual microscopy approach by a group of 13 pathologists with expertise in thymic tumours over a period of 6 years. The specimens were classified according to the WHO 2015 classification. The data were subjected to statistical analysis, and interobserver concordance (Fleiss kappa) was calculated. All cases were diagnosed within a time frame of 2 weeks. The overall level of agreement was substantial (κ = 0.6762), and differed slightly between resection specimens (κ = 0.7281) and biopsies (κ = 0.5955). When analysis was limited to thymomas only, and they were grouped according to the European Society for Medical Oncology Clinical Practice Guidelines into B2, B3 versus A, AB, B1 and B3 versus A, AB, B1, B2, the level of agreement decreased slightly (κ = 0.5506 and κ = 0.4929, respectively). Difficulties arose in distinguishing thymoma from thymic carcinoma. Within the thymoma subgroup, difficulties in distinction were seen within the B group. CONCLUSIONS: Agreement in diagnosing thymic lesions is substantial when they are assessed by pathologists with experience of these rare tumours. Digital pathology decreases the turnaround time and facilitates access to what is essentially a multinational resource. This platform provides a template for dealing with rare tumours for which expertise is sparse.
Authors 7
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Leiden University · Erasmus MC · Erasmus University Rotterdam
Affiliation as printed
Department of Pathology Erasmus MC Rotterdam The Netherlands
Erasmus Univ, Erasmus University Rotterdam, Erasmus University Medical Center, Oncode Inst, Erasmus MC, Med Ctr Rotterdam
Leiden Univ, Leiden University, Leiden Univ Med Ctr, Leiden Amsterdam Ctr Drug Res, Div Med Pharmacol
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Royal Brompton & Harefield NHS Foundation Trust · Harefield Hospital · Imperial College London
Affiliation as printed
Department of Histopathology Royal Brompton & Harefield NHS Foundation Trust London UK
National Heart and Lung Institute Imperial College London London UK
Imperial Coll Kensington, Imperial College London, Natl Heart & Lung Inst
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Affiliation as printed
Department of Laboratory Medicine and Pathology Mayo Clinic Rochester MN USA
Mayo Clin, Mayo Clinic, Mayo Med Sch
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Universitätsmedizin Göttingen · University of Göttingen
Affiliation as printed
Universitätsklinikum Göttingen Göttingen Germany
Univ Med Ctr Gottingen, University of Gottingen, Inst Pathol
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University Medical Center Groningen · University of Groningen
Affiliation as printed
University Medical Centre Groningen Groningen The Netherlands
Groningen Research Institute for Asthma and COPD (GRIAC)
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The University of Texas MD Anderson Cancer Center
Affiliation as printed
MD Anderson Cancer Center Houston TX USA
Univ Texas MD Anderson Canc Ctr, UTMD Anderson Cancer Center, University of Texas System, Dept Neurooncol
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Erasmus MC · Erasmus University Rotterdam
Affiliation as printed
Department of Pathology Erasmus MC Rotterdam The Netherlands
Erasmus Univ, Erasmus University Rotterdam, Erasmus University Medical Center, Oncode Inst, Erasmus MC, Med Ctr Rotterdam
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