AB032. Central pathology review of thymic tumors: updated analysis of diagnostic concordance in the French RYTHMIC cohort—a retrospective study
Original Research

AB032. Central pathology review of thymic tumors: updated analysis of diagnostic concordance in the French RYTHMIC cohort—a retrospective study

Álvaro López-Gutiérrez1, Lara Chalabreysse2, Jean-Philippe Dales3, Romain Dubois4, Véronique Hofman5, Audrey Mansuet-Lupo6, Anne de Muret7, Nicolas Piton8, Isabelle Rouquette9, Véronique Secq3, Damien Sizaret7, Vincent Thomas de Montpréville10, José Carlos Benítez11, Angela Botticella12, Daniela Miliziano1, Lodovica Zullo1, Pascale Missy13, Jordi Remón1, Nicolas Girard14, Benjamin Besse1, Thierry Jo Molina15

1Cancer Medicine Department, Gustave Roussy, Villejuif, France; 2Department of Pathology, Hôpital Louis-Pradel, Lyon, France; 3Department of Pathology, Hôpital Nord, AP-HM, Marseille, France; 4Department of Pathology, University Hospital of Lille, Lille, France; 5Laboratory of Clinical and Experimental Pathology, IHU RespirERA, Nice Hospital, University Côte d'Azur, Nice, France; 6Department of Pathology, Cochin Hospital, Université Paris Cité, Paris, France; 7Department of Pathology, Tours University Hospital, Tours, France; 8Department of Pathology, Rouen University Hospital, Rouen, France; 9Department of Pathology, University Cancer Institute Toulouse-Oncopole, Toulouse, France; 10Department of Pathology, Hôpital Marie Lannelongue, Le Plessis-Robinson, France; 11Department of Medical Oncology, University Hospital Virgen de la Victoria, Málaga, Spain; 12Department of Radiation Oncology, Gustave Roussy, Villejuif, France; 13French Cooperative Thoracic Intergroup (IFCT), Paris, France; 14Institut du Thorax Curie-Montsouris, Institut Curie, Paris, France; 15Department of Pathology, Necker’s et Enfants University Hospital, Paris, France

Correspondence to: Álvaro López Gutiérrez, MD. Cancer Medicine Department, Gustave Roussy, 114 Rue Edouard Vaillant, Villejuif, Île-de-France, 94800, France. Email: alvaro.lopez-gutierrez@gustaveroussy.fr.

Background: Thymic epithelial tumors (TETs) are rare malignancies with variable histological subtypes and clinical behavior. Accurate classification of histotype and stage is essential for guiding postoperative radiotherapy (PORT) and systemic therapy. A previous national study conducted by the RYTHMIC network (France) on cases diagnosed from 2012 to 2016 identified a 6% rate of major diagnostic discrepancies between local and expert pathology reviews (Molina et al., Eur J Cancer 2021). A follow-up study was conducted to assess the frequency and clinical relevance of such discrepancies in a larger cohort.

Methods: This retrospective study included all patients with suspected or confirmed TETs discussed at the RYTHMIC national tumor board between January 2017 and December 2023. Expert pathology review was conducted by at least two specialized pathologists. Diagnoses were classified according to World Health Organization (WHO) 2015 criteria and Masaoka-Koga (MK) staging. Discordances between initial and expert diagnoses were recorded for histotype and/or stage, and categorized as minor or major based on potential clinical impact. Cases were considered non-evaluable when either the initial diagnosis or the expert review lacked sufficient material or contextual data (e.g., biopsy-only samples, absence of operative reports) to reliably assess the histotype and/or MK stage.

Results: A total of 1,334 cases were reviewed. Initial and central diagnoses were concordant in 623 cases (46.7%). Discordances were observed in 415 cases (31.1%), of which 323 (24.2%) were minor and 92 (6.9%) were major. In addition, 296 cases (22.2%) were classified as non-evaluable. Among the 92 major discordances, 59 (64.1%) would have altered the indication for PORT, 7 (7.6%) would have changed systemic therapy or follow-up, and 23 (28.2%) involved a diagnosis outside the TET spectrum (e.g., lymphoma, metastatic carcinoma, thymic hyperplasia).

Conclusions: This updated analysis confirms the continued relevance of expert pathology review in TETs. Although major discrepancies remained at a similar rate to the previous study, most had significant therapeutic consequences. The presence of misdiagnoses outside the TET spectrum underscores the need for systematic expert validation. Given the rate of discordance, future integration of AI -based classification systems may offer complementary support in the diagnosis of TETs.

Keywords: Thymic epithelial tumors (TETs); central pathology review; diagnostic discordance

Acknowledgments

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Footnote

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://med.amegroups.com/article/view/10.21037/med-25-ab032/coif). V.T.d.M. serves as an unpaid editorial board member of Mediastinum from May 2025 to December 2026. N.G. and T.J.M. serve as unpaid editorial board members of Mediastinum from January 2024 to December 2025. The other authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The RYTHMIC observational study (IFCT-1104 E-RYTHMIC) received favorable opinions from the Comité d'Évaluation des Protocoles (CEPRO) of the Société de Pneumologie de Langue Française (14 December 2014) and the Comité Consultatif sur le Traitement de l’Information en matière de Recherche dans le domaine de la Santé (CCTIRS, No. 15.135bis, 23 March 2016), and was authorized by the Commission Nationale de l’Informatique et des Libertés (CNIL, No. 916181, 24 May 2016). In accordance with French law, individual consent for this retrospective analysis was waived, and patient non-opposition was systematically sought by the treating physician.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

doi: 10.21037/med-25-ab032
Cite this abstract as: López-Gutiérrez Á, Chalabreysse L, Dales JP, Dubois R, Hofman V, Mansuet-Lupo A, de Muret A, Piton N, Rouquette I, Secq V, Sizaret D, Thomas de Montpréville V, Benítez JC, Botticella A, Miliziano D, Zullo L, Missy P, Remón J, Girard N, Besse B, Molina TJ. AB032. Central pathology review of thymic tumors: updated analysis of diagnostic concordance in the French RYTHMIC cohort—a retrospective study. Mediastinum 2025;9:AB032.

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