Pathological discrepancies in the diagnosis of thymic epithelial tumors: the Tallinn-Lyon experience

Abstract

Background: Thymic epithelial tumors are rare thoracic tumors for which pathological diagnosis is challenging due to the definition of multiple subtypes, tumor heterogeneity, and variations in interobserver reproducibility. In this study, we aimed at analyzing the quality of pathological reporting in line with the consistency between initial diagnosis and final diagnosis after expert review through a collaboration between the largest thoracic oncology center in Estonia, and one expert center in France. Methods: Hospital electronic database and pathology databases from the Tallinn North Estonia Medical Centre were searched for thymic and mediastinal tumors from 2010 to 2017. Pathology specimens were referred to the Pathology Department of the Lyon University hospital. Overall, 55 tissue specimens from 49 patients were included. Results: From pathology reports, tumor size, diagnosis, and invasion had been mentioned in ≥80% of cases, while resection status and staging were assessed in only 48% and 17% of cases, respectively. The initial diagnosis was consistent with that of the review in 60% of cases. Diagnostic concordance for thymoma subtypes was low (Cohen's kappa 0.34, 95% CI: 0.16-0.52). Overall, a major change in the management of 8 (16%) patients had to be made after pathological review: 3 patients had a normal thymus according to the reference centre, while thymoma B1 or B2 had been diagnosed locally; 5 additional patients had a final diagnosis of non-thymic tumor. Conclusions: Implementing structured pathology reports may help to decrease discrepancies in the diagnosis of thymic epithelial tumors. The development of expert networks is an opportunity to improve diagnosis and patient care, particularly in regard to rare cancers.

Accuracy of pathologic diagnosis for thymic epithelial tumors: a brief report from an Italian reference Center

“…The authors from a large Estonian Center identified 49 TET patients, whose pathologic specimens were systematically sent to a French reference Institution with a high expertise in the disease. The concordance rate reported in this work was higher than in our case series, as the initial diagnosis was consistent with pathologic second look in 60% of cases, with only 16% of major changes [15]. The difference between the results may be attributed to the nature of the involved Centers, as the Estonian hospital was the largest oncologic Institution in that Country, as documented by the availability of a relatively large case series of TETs.…”

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

“…This might be explained by the number of evaluating pathologists, the heterogeneity of the thymic lesions, the experience of the assessors, and the amount and variability of cases and additional stains evaluated. [8][9][10] Evaluation of TETs by a small number of assessors will usually lead to less interobserver variability, particularly if the assessors are within a single institute and frequently discuss cases. 11,16,17 To maximise accuracy in diagnosing thymic tumours, changes were introduced in the 2015 WHO classification, 3 as exemplified in detail in the assessment of the International Thymic Malignancy Interest Group statement on the WHO histological classification.…”

“…In these studies, the range of agreement ranged from fair to substantial to almost perfect, with κ ‐values between 0.34 and 0.87. This might be explained by the number of evaluating pathologists, the heterogeneity of the thymic lesions, the experience of the assessors, and the amount and variability of cases and additional stains evaluated 8–10 . Evaluation of TETs by a small number of assessors will usually lead to less interobserver variability, particularly if the assessors are within a single institute and frequently discuss cases 11,16,17 …”

“…Most difficulties were encountered in the subclassification of type B thymomas. [8][9][10][11][12] In recognition of these classification difficulties, diagnostic panels have been set up to improve consistency and aid the harmonisation of reporting.…”

“…The level of interobserver agreement varies widely within the studies, with κ ‐values ranging between 0.37 and 0.87. Most difficulties were encountered in the subclassification of type B thymomas 8–12 . In recognition of these classification difficulties, diagnostic panels have been set up to improve consistency and aid the harmonisation of reporting.…”