# The 2021 WHO classification of tumours of the thymus and mediastinum: what is new in thymic epithelial, germ cell and mesenchymal tumours

Source: https://onco.cc/key-papers/paper-who-2021-thymus-mediastinum-classification-marx-jto-2022/  
OnCo record `paper-who-2021-thymus-mediastinum-classification-marx-jto-2022` (Key paper). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

The current WHO scheme for thymic tumours, which keeps the type A to B3 thymoma letters and the separate category of thymic carcinoma while adding new molecular entities.

## Summary

Summary by members of the WHO editorial board of the fifth-edition classification of thymic and mediastinal tumours: thymoma types A, AB, B1, B2 and B3 and their rarer variants, thymic carcinomas (squamous, basaloid, mucoepidermoid, lymphoepithelial, NUT carcinoma and others), thymic neuroendocrine neoplasms, and mediastinal germ cell and mesenchymal tumours.

It highlights immunohistochemical and molecular markers (such as GTF2I mutations in type A and AB thymomas and NUTM1 fusions in NUT carcinoma), the requirement to report all thymomas as malignant, and the alignment with TNM staging.

## Fields

- Kind: Key paper
- Last checked: 2026-09-18
- Journal: Journal of Thoracic Oncology
- Year: 2022
- DOI: 10.1016/j.jtho.2021.10.010
- Authors: Marx A, Chan JKC, Chalabreysse L, et al.
- What it means: The names on a thymic pathology report, and the sharp line between thymoma and thymic carcinoma that drives treatment, come from this classification.
- Caveats: Interobserver agreement on thymoma subtypes remains imperfect.; Molecular markers are diagnostic aids rather than treatment targets so far.

## Sources

- J Thorac Oncol 2022: https://doi.org/10.1016/j.jtho.2021.10.010
- PubMed: https://pubmed.ncbi.nlm.nih.gov/34695605/

## Connected records

- cancers: [Thymic carcinoma](https://onco.cc/cancers/thymic-carcinoma/), [Thymoma (WHO types A, AB, B1, B2 and B3)](https://onco.cc/cancers/thymoma/)
- journals: [Journal of Thoracic Oncology](https://onco.cc/journals/journal-of-thoracic-oncology/)

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