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. 2013 Mar;79(3):236-41.
doi: 10.1016/j.lungcan.2012.11.015. Epub 2012 Dec 29.

Reproducibility of the WHO classification of thymomas: practical implications

P A Zucali  1 , L Di Tommaso, I Petrini, S Battista, H S Lee, M Merino, E Lorenzi, E Voulaz, F De Vincenzo, M Simonelli, M Roncalli, L Giordano, M Alloisio, A Santoro, G Giaccone
Affiliations

Reproducibility of the WHO classification of thymomas: practical implications

P A Zucali et al. Lung Cancer. 2013 Mar.

Abstract

Background: The WHO-classification was shown to be an independent prognostic marker in some but not all retrospective studies possibly due to lack of reproducibility. We investigated the reproducibility of the WHO-classification and its prognostic implication using a large series of resected thymomas.

Methods: Four independent pathologists histologically classified a surgical series of 129 thymic tumors in a blinded fashion. Fleiss' kappa-coefficient was used to assess the pathologists' overall agreement, and Cohen-Kappa to assess the agreement between two observers. Disease-related-survival (DRS) and progression-free-survival (PFS) curves were generated by Kaplan-Meier method and compared by log-rank test.

Results: In 63/129 (48.8%) cases there was a complete agreement; in 43/129 (33.3%) cases 3/4 pathological diagnoses were identical; in 15/129 (11.6%) cases the diagnoses were identical by pair; in 8/129 (6.2%) cases three different pathological diagnoses were on record. The Kappa-correlation coefficient was only moderate (0.53). A following web review carried out on the 23 cases with at least two different diagnoses reached a complete consensus. The histotype showed a statistically significant impact on PFS and DRS in the classification provided by only two pathologists.

Conclusions: In this study, the agreement on WHO classification of thymomas was only moderate and this impacted on patients management. Web consensus conference on the diagnosis, more stringent diagnostic criteria or the adoption of referral diagnostic centres may substantially reduce discrepancies.

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Conflict of interest statement

Conflict of interest statement

None declared. All authors disclose any actual or potential conflict of interest including any financial, personal or other relationships with other people or organizations that could inappropriately influence (bias) this work.

Conflict of interest statement

We did not receive any financial, material, and specific funding for this work. All authors have no relevant financial interests in this manuscript.

Figures

Figure 1
Figure 1
A thymic tumor characterized by well demarcated lobules (A); even at scanning magnification these lobules show different amount of epithelial cells (B); in some ares neoplastic cells are characterized by a larger amount of cytoplasm and vescicular nuclei with small but distinct nucleoli (C); most of the fields, however, are characterized by few neoplastic cells intermingled among several lymphocytes. This lesion was classified as type B1 (n° 2) and B2 (n° 2) thymomas.
Figure 2
Figure 2
A thymic tumor made by neoplastic cells with prominent eosinophilic nucleoli, a “syncitial” appearance, arrangend in lobules separated by lymphocytes. This lesion was classified as thymic carcinoma (n° 2), type A (n° 1) and type B3 thymoma (n° 1).
See this image and copyright information in PMC

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