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# Pleural tumours: mesothelioma and solitary fibrous tumour

- Lesion

Mesothelioma is an aggressive cancer of the pleural lining caused mostly by asbestos. Solitary fibrous tumour is a usually benign pleural mass.

Updated Nov 12, 2026

## Key points

- Mesothelioma: asbestos exposure in most cases; latency of 25 to 45 years; smoking adds no risk.
- Genetics: CDKN2A deletion (9p) in most, BAP1 and NF2 mutations; germline BAP1 mutation raises risk.
- Types: epithelioid (most common, best prognosis), sarcomatoid, biphasic.
- IHC: mesothelioma positive for calretinin, WT1, CK5/6, podoplanin (D2-40); negative for claudin-4, BerEP4, TTF-1, CEA (the adenocarcinoma markers).
- Loss of BAP1 staining supports malignancy versus reactive mesothelium.
- Solitary fibrous tumour: pedunculated, CD34 and STAT6 positive, keratin negative (the opposite of mesothelioma).

On this page

- The basics Key points
- What it is
- Structure
- Step by step
- Mesothelioma vs lung adenocarcinoma in the pleura
- Markers
- Memory aid
- Elsewhere in DurgiPedia

- Clinical Clinical notes

- Study Test yourself

- Connections Connections

## What it is

Most tumours in the pleura are metastases, especially from lung and breast. The two primary tumours to know are malignant mesothelioma, a diffuse asbestos-related cancer with a latency of decades and a poor prognosis, and solitary fibrous tumour, a localised fibroblastic tumour defined by a NAB2::STAT6 fusion and unrelated to asbestos. Immunohistochemistry separates mesothelioma from adenocarcinoma.

## Structure

- Mesothelioma gross: thick, soft, gelatinous grey-pink rind that encases the lung and fills the fissures, with effusion.
- Epithelioid: cuboidal or flattened cells forming tubules and papillae, like adenocarcinoma.
- Sarcomatoid: malignant spindle cells like a sarcoma; biphasic: both.
- Solitary fibrous tumour: firm, well-circumscribed mass on a pedicle; patternless spindle cells among collagen and branching staghorn vessels.

## Step by step

- Inhaled asbestos fibres (especially amphiboles) migrate to the pleura.
- Fibres cause chronic inflammation, oxidant injury and DNA damage in mesothelial cells.
- Over decades the cells lose CDKN2A, BAP1 and NF2 tumour suppressors.
- The tumour spreads over the pleural surfaces and invades the chest wall, lung and mediastinum.
- Solitary fibrous tumour arises from a NAB2::STAT6 fusion that creates a chimeric transcription factor.

## Mesothelioma vs lung adenocarcinoma in the pleura

| Feature | Epithelioid mesothelioma | Adenocarcinoma |
| --- | --- | --- |
| [Growth](https://durgical.com/en/conditions/malignant-pleural-mesothelioma/) | Diffuse rind encasing the lung | Mass in the lung, pleural nodules |
| [Positive markers](https://durgical.com/en/conditions/lung-cancer/) | Calretinin, WT1, CK5/6, D2-40 | TTF-1, napsin A, claudin-4, BerEP4, CEA |
| Main cause | Asbestos | Tobacco |
| Smoking effect | No added risk | Strong risk factor |

## Markers

- Calretinin
- WT1
- CK5/6
- D2-40 (podoplanin)
- BAP1 loss
- STAT6
- CD34

## Clinical notes

- Mesothelioma: chest pain, dyspnoea and recurrent effusions; asbestosis is present in only a minority.
- Median survival is about a year; peritoneal, pericardial and tunica vaginalis mesotheliomas also occur.
- Solitary fibrous tumour can cause hypoglycaemia (IGF-2) or clubbing; resection is usually curative.

## Memory aid

Mesothelioma: Calretinin and WT1 Wrap the lung; adenocarcinoma: TTF-1 Travels from inside.

## Test yourself

Think of the answer, then tap the question to see it.

## Which immunohistochemical markers support mesothelioma over adenocarcinoma?

Calretinin, WT1, CK5/6 and podoplanin positive, with claudin-4, BerEP4 and TTF-1 negative.

## What is the latency between asbestos exposure and mesothelioma?

Usually decades, about 25 to 45 years.

## What fusion gene defines solitary fibrous tumour?

NAB2::STAT6, shown by nuclear STAT6 staining.

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## Elsewhere in DurgiPedia

- [Serous membranes: pleura and peritoneum](https://durgical.com/en/histology/serous-membranes-pleura-and-peritoneum/)

## Connections

## Related 5

- [Immunohistochemistry: the principle and the markers to know](https://durgical.com/en/general-pathology/immunohistochemistry-the-principle-and-the-markers-to-know/)
- [Chemical carcinogens: initiation, promotion and the table to know](https://durgical.com/en/general-pathology/chemical-carcinogens-initiation-promotion-and-the-table-to-know/)
- [Asbestos-related disease](https://durgical.com/en/general-pathology/asbestos-related-disease/)
- [Pleural effusion and pneumothorax](https://durgical.com/en/general-pathology/pleural-effusion-and-pneumothorax/)
- [Lung carcinoma: histologic types](https://durgical.com/en/general-pathology/lung-carcinoma-histologic-types/)

## Related conditions 1

- [Malignant pleural mesothelioma](https://durgical.com/en/conditions/malignant-pleural-mesothelioma/)

[← All of general pathology](https://durgical.com/en/general-pathology/)

Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: [Mesothelioma](https://medlineplus.gov/mesothelioma.html) (MedlinePlus, US National Library of Medicine, 2025); [Pleural Disorders](https://medlineplus.gov/pleuraldisorders.html) (MedlinePlus, US National Library of Medicine, 2025).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/general-pathology/pleural-tumours-mesothelioma-and-solitary-fibrous-tumour/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/pleural-tumours-mesothelioma-and-solitary-fibrous-tumour/