Interobserver variation in the classification of thymic lesions including biopsies and resection specimens in an international digital microscopy panel

Wolf, J. L., van Nederveen, F., Blaauwgeers, H., Marx, A., Nicholson, A. G., Roden, A. C., Ströbel, P., Timens, W., Weissferdt, A., von der Thüsen, J. & den Bakker, M. A., 7-Jun-2020, In : Histopathology. 16 p.

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  • Interobserver variation in the classification of thymic lesions including biopsies and resection

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  • Janina L Wolf
  • Francien van Nederveen
  • Hans Blaauwgeers
  • Alexander Marx
  • Andrew G Nicholson
  • Anja C Roden
  • Philipp Ströbel
  • Wim Timens
  • Annika Weissferdt
  • Jan von der Thüsen
  • Michael A den Bakker

INTRODUCTION: Thymic tumours are a rare in routine pathology practice. Although the 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 in a large group of international pathologists with expertise in thymic pathology and by using whole slide imaging (WSI) to facilitate rapid diagnostic turnover.

METHODS: 305 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 six years. The specimens were classified according to the WHO2015 classification. The data was subjected to statistical analysis and interobserver concordance (Fleiss Kappa) was calculated.

RESULTS: All cases were diagnosed withing a time frame of two 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 limited to thymomas only and grouping them according to the ESMO Clinical Practice Guidelines into [B2, B3] vs [A, AB, B1] and [B3] vs [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 assessed by pathologists with experience in these rare tumours. Digital pathology decreases turn-around 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.

Original languageEnglish
Number of pages16
Publication statusE-pub ahead of print - 7-Jun-2020

ID: 127337235