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Thymoma and pleural mesothelioma
Thymoma is an anterior mediastinal tumour linked to autoimmune disease (mainly myasthenia) and treated mainly by complete resection; pleural mesothelioma is linked to asbestos, diagnosed by thoracoscopic biopsy, and treated mainly with systemic therapy — nivolumab with ipilimumab or platinum-pemetrexed chemotherapy.
Why it matters in the exam
Both tumours appear in the thoracic part of the exam. For thymoma the questions ask about an anterior mediastinal mass in a patient with myasthenia, treatment of locally advanced disease and the place of adjuvant radiation. For mesothelioma they ask about work-up of a pleural effusion with negative cytology and treatment of unresectable disease.
Remember the differential diagnosis of an anterior mediastinal mass: thymoma, germ cell tumour and teratoma, thyroid mass and lymphoma. In a young man with an anterior mediastinal mass check β-hCG and AFP. In thymoma acetylcholine receptor antibodies must be checked before surgery, and immunotherapy needs special caution because of a high risk of severe immune effects.
Key points
- Thymoma is an anterior mediastinal tumour, linked to myasthenia and autoimmune disease, and treated mainly by complete resection.
- In thymoma stage III or after incomplete resection radiation is added, and in locally advanced disease chemotherapy is given before surgery.
- Pleural mesothelioma is linked to asbestos, and when suspected with negative cytology a thoracoscopic biopsy is done.
- In mesothelioma the epithelioid type has the best prognosis, and the sarcomatoid type is the worst and responds less to chemotherapy.
- Unresectable mesothelioma is treated with nivolumab plus ipilimumab or with platinum-pemetrexed chemotherapy.
Summary table
| Issue | Thymoma | Pleural mesothelioma |
|---|---|---|
| Risk factors and associations | Myasthenia, pure red cell aplasia, hypogammaglobulinaemia | Asbestos exposure, with a latency of decades; BAP1 loss |
| Presentation | Anterior mediastinal mass, sometimes found during myasthenia work-up | Dyspnoea, chest pain and a unilateral pleural effusion |
| Diagnosis | CT or MRI; for a mass that looks resectable — resection without prior biopsy | Fluid cytology is often negative — thoracoscopic biopsy |
| Classification | WHO: A, AB, B1–B3 and thymic carcinoma; Masaoka stages | Epithelioid (better), sarcomatoid (worse), biphasic |
| Resectable disease | Complete resection of the thymus and tumour | Surgery only in selected cases, mainly the epithelioid type |
| Locally advanced disease | Neoadjuvant chemotherapy then surgery; adjuvant radiation after incomplete resection or in stage III | Nivolumab with ipilimumab (mainly in the non-epithelioid type), or cisplatin with pemetrexed, possibly with immunotherapy |
| Caution | Check acetylcholine receptor antibodies before surgery; immunotherapy is riskier | No routine prophylactic radiation to intervention tracts |
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Sources
- NCCN Clinical Practice Guidelines in Oncology: Thymomas and Thymic Carcinomas; Mesothelioma: Pleural, 2026 — Primary treatment
- ESMO Clinical Practice Guideline: Thymic epithelial tumours, 2015 — Diagnosis, treatment and follow-up
- ESMO Clinical Practice Guideline: Malignant pleural mesothelioma, 2022 — Diagnosis, treatment and follow-up
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.