Key Takeaways
- Malignant pleural mesothelioma (MPM) is the most common form of mesothelioma. Patients typically present with chest pain and breathlessness caused by fluid buildup between the layers of tissue lining the lungs (pleural effusion).
- Diagnosing mesothelioma involves multiple imaging tests — including chest X-ray, thoracic ultrasound, CT scan, PET-CT scan, and MRI — each serving a different purpose from initial detection to staging and biopsy planning.
- A negative CT or PET-CT scan does not always rule out mesothelioma — 35 to 46 percent of patients with pleural malignancy initially receive a benign CT report, making follow-up testing critical.
- Mesothelioma has three cell subtypes — epithelioid, sarcomatoid, and biphasic — and correctly identifying the subtype is essential because each has a different prognosis and responds differently to treatment.
- First-line treatment is typically chemotherapy with pemetrexed and cisplatin, which in a randomized study of 456 patients improved median survival from 9.3 months to 12.1 months.
- Emerging treatments include immune checkpoint inhibitors (anti-CTLA-4 and anti-PD-1/PD-L1 agents) and oncolytic viral therapy, which uses modified viruses to target and destroy tumor cells.
Malignant pleural mesothelioma (MPM) is a thoracic malignancy and the most common form of mesothelioma. Patients may come in to see a doctor with chest pain and breathlessness related to a pleural effusion, which is a pathologic collection of fluid between the visceral and parietal pleura in the thoracic cavity.
Testing
There are a variety of imaging tests that can be done to attempt to detect mesothelioma. A chest radiography usually shows a pleural effusion or a pleural mass. A thoracic ultrasound can also be done in order to estimate the size of an effusion. A CT scan can also be helpful when diagnosing MPM. However, 35 to 46 percent of patients who have pleural malignancy have a benign CT report. A negative PET-CT scan may not tell the full story, so there should be more investigations to see if there are no signs of mesothelioma from this scan. A PET-CT scan can be done to locate the best area for histological sampling.
PET-CT is usually used to stage MPM, because its diagnostic accuracy is high. It can identify extra-thoracic metastases. An MRI will show a more precise guess at pleural tumor volume.
Subtypes
There are subtypes of mesothelioma which include epithelioid, sarcomatoid and biphasic mesothelioma. It is important to identify these subtypes as they have a direct correlation to prognosis. Epithelioid mesotheliomas look like carcinomas from a morphological sense and usually are accompanied with pleural effusions, while sarcomatoid mesotheliomas look like sarcomas and are accompanied with pleural masses. It can be hard to determine the subtype of mesothelioma that a patient has. Identifying molecular-based biomarkers can be more informative and allow for better, more specialized treatment.
It is thought that MPM patients may benefit from oncolytic viral therapy, which uses modified viruses to infect and destroy tumor cells and is used to fight many cancers.
Immune checkpoint inhibitors have been tested for the treatment of MPM. CTLA-4 is an immune suppressive receptor that inhibits T-cell responses. Anti-CTLA-4 was given to mice with mesothelioma; it affected tumor growth and increased overall survival. Another immune checkpoint is PD-1 /PD-L1 PD-1. Anti-PD-L1 or PD-1 agents have been studied.
Processes
There are different processes that may take place in the body because of asbestos exposure. Asbestos fibers may penetrate mesothelial cells and disrupt mitotic spindles causing chromosomal abnormalities. Also, the death of mesothelial cells due to asbestos leads to release of high mobility group box 1, which then leads to chronic inflammation. Additionally, macrophages try to digest asbestos fibers, but they are not able to, resulting in the production of reactive oxygen species, which causes intracellular DNA damage and abnormal repair. Additionally, when someone inhales asbestos fibers it causes irritation, leading to tissue damage. These are just a sampling of the multitude of disruptive processes that can take place within the body due to asbestos exposure.
First line therapy for mesothelioma tends to be chemotherapy which emerged from a study by Vogelzang. Based on a randomized study of 456 mesothelioma patients being treated with a combination of pemetrexed and cisplatin, there was an improved survival rate from 9.3 months to 12.1 months.
If you or a loved one has been diagnosed with an asbestos-related disease, please call (800) 505-6000 for legal help. For more information, fill out the form on our Homepage.
Frequently Asked Questions
What tests are used to diagnose mesothelioma?
Multiple imaging tests may be used in combination to detect and diagnose mesothelioma:
- Chest X-ray (radiography) — typically the first test, which can reveal a pleural effusion or pleural mass
- Thoracic ultrasound — used to estimate the size of a pleural effusion
- CT scan — provides detailed images, though 35–46% of patients with pleural malignancy initially receive a benign CT report
- PET-CT scan — has high diagnostic accuracy for staging mesothelioma, can identify cancer spread beyond the chest, and helps locate the best area for tissue sampling
- MRI — provides a more precise estimate of pleural tumor volume
Because no single test is definitive, doctors often use multiple tests in sequence to build a complete picture. A negative scan does not always rule out mesothelioma.
Can a CT scan miss mesothelioma?
Yes. Research shows that 35 to 46 percent of patients who have pleural malignancy initially receive a benign CT report. This is why doctors typically use multiple diagnostic methods — including PET-CT scans, MRIs, and biopsies — rather than relying on a single test. If mesothelioma is suspected based on symptoms and asbestos exposure history, further investigation is warranted even after a negative CT scan.
What are the subtypes of mesothelioma and why do they matter?
There are three mesothelioma cell subtypes:
- Epithelioid — the most common subtype, which resembles carcinomas and is usually accompanied by pleural effusions. Generally has the best prognosis and responds most favorably to treatment.
- Sarcomatoid — resembles sarcomas and is typically accompanied by pleural masses. Tends to be more aggressive and harder to treat.
- Biphasic — contains both epithelioid and sarcomatoid cells. Prognosis depends on which cell type is more dominant.
Identifying the correct subtype is critical because it directly affects prognosis and determines which treatments are most likely to be effective. Molecular-based biomarkers may help provide even more precise identification for specialized treatment planning.
What is the standard first-line treatment for mesothelioma?
The standard first-line treatment for malignant pleural mesothelioma is chemotherapy using a combination of pemetrexed and cisplatin. This protocol emerged from a landmark randomized study of 456 mesothelioma patients, which showed that the combination improved median survival from 9.3 months to 12.1 months compared to cisplatin alone.
What are immune checkpoint inhibitors and how are they used for mesothelioma?
Immune checkpoint inhibitors are a form of immunotherapy that helps the body’s immune system recognize and attack cancer cells. Two types being studied for mesothelioma treatment are:
- Anti-CTLA-4 agents — CTLA-4 is a receptor that suppresses the immune system’s T-cell responses. Blocking it with anti-CTLA-4 therapy has been shown in studies to slow tumor growth and increase survival in mesothelioma.
- Anti-PD-1/PD-L1 agents — PD-1 is another immune checkpoint that cancer cells can exploit to avoid detection. Blocking it may allow the immune system to more effectively target mesothelioma cells.
These therapies represent a growing area of mesothelioma treatment and may be used alongside or after traditional chemotherapy.
What is oncolytic viral therapy?
Oncolytic viral therapy is an emerging treatment approach that uses genetically modified viruses to infect and destroy tumor cells. The modified viruses are designed to target cancer cells specifically while leaving healthy cells intact. While this therapy is used to fight many types of cancer, researchers believe it may be particularly beneficial for mesothelioma patients. It is still considered an experimental treatment and is typically available through clinical trials.
How does asbestos cause mesothelioma at the cellular level?
Asbestos causes damage through several biological processes:
- Asbestos fibers can penetrate mesothelial cells and disrupt cell division, causing chromosomal abnormalities
- When mesothelial cells die from asbestos damage, they release a protein called high mobility group box 1 (HMGB1), which triggers chronic inflammation
- Immune cells called macrophages attempt to digest asbestos fibers but cannot, producing reactive oxygen species that damage DNA and lead to abnormal cell repair
- Inhaled asbestos fibers cause ongoing tissue irritation and damage in the lungs and pleural lining
These processes can unfold over decades, which is why mesothelioma typically develops 20 to 50 years after initial asbestos exposure.
What should I do if I’ve been diagnosed with mesothelioma?
If you or a loved one has been diagnosed with mesothelioma or another asbestos-related disease, understanding your diagnosis, treatment options, and legal rights is an essential first step. Call (800) 505-6000 or fill out our contact form for a free consultation and to request our Pennsylvania Mesothelioma Information Guide.
