U01.16.036 Mesothelioma

Mesothelioma is a malignancy of the pleura primarily associated with exposure to asbestos. It is characterized by various clinical and histological features, including pleural effusion and specific markers.

Pathophysiology

Association with Asbestosis: Mesothelioma is commonly linked to asbestos exposure, which leads to malignant transformation of mesothelial cells.
Pleural Involvement: The cancer typically manifests in the pleura, resulting in complications such as pleural thickening and hemorrhagic pleural effusion.

Clinical Features

Hemorrhagic Pleural Effusion: Patients may present with exudative pleural effusion, which is often bloody.
Pleural Thickening: Imaging may reveal thickened pleura, indicating the presence of malignant tissue.

Histological Characteristics

Psammoma Bodies: These calcified structures are commonly seen on histological examination of mesothelioma tissue.

Immunohistochemistry

Markers:
- Calretinin: Positive in almost all cases of mesothelioma.
- Cytokeratin 5/6: Also positive in nearly all mesothelioma cases.
- Cytokeratin 7 and 20: Typically negative in mesothelioma, aiding in differentiation from carcinomas.
Differentiation from Carcinomas:
- Calretinin and cytokeratin 5/6 positivity helps distinguish mesothelioma from most carcinomas, which are usually negative for these markers.

Risk Factors

Non-Smoking: Smoking is not considered a risk factor for mesothelioma, differentiating it from many other lung-related malignancies.

Points to Remember

Mesothelioma is primarily linked to asbestos exposure.
Key histological features include the presence of psammoma bodies.
Immunohistochemical markers, particularly calretinin and cytokeratin 5/6, are essential for diagnosis.
Hemorrhagic pleural effusion is a common clinical manifestation.

Tables

Characteristic	Mesothelioma	Carcinoma
Asbestos Association	Yes	No
Psammoma Bodies	Commonly present	Rare
Calretinin	Positive	Negative (mostly)
Cytokeratin 5/6	Positive	Negative (mostly)
Smoking Risk	Not a risk factor	Risk factor

Bibliography

Robinson, B. W., & Lake, R. A. (2005). “Advances in malignant mesothelioma.” New England Journal of Medicine, 353(15), 1591-1603. Link
Yang, H., & Wang, J. (2010). “Asbestos and malignant mesothelioma: A review of the evidence.” Occupational and Environmental Medicine, 67(12), 874-877. Link
Hwang, H. S., & Kim, J. H. (2017). “Immunohistochemical features of mesothelioma.” Journal of Clinical Pathology, 70(6), 481-487. Link

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