What Tests are Used to Diagnose Mesothelioma?

Imaging Tests

Imaging tests are typically the first step in diagnosing mesothelioma. These tests help visualize the internal structures of the body, identify abnormalities, and determine the location and extent of the disease.

X-rays

• Purpose: X-rays are often the initial imaging test performed when mesothelioma is suspected, especially if the patient presents with symptoms such as chest pain or shortness of breath.
• What It Shows: X-rays can reveal pleural effusion (fluid buildup between the lung and chest wall), pleural thickening, or masses in the lungs or abdomen, which might suggest mesothelioma.

Computed Tomography (CT) Scan

• Purpose: A CT scan provides more detailed images than an X-ray and is commonly used to evaluate suspicious findings on an X-ray.
• What It Shows: CT scans offer cross-sectional images of the chest or abdomen, helping to identify the size, shape, and location of tumors. CT scans are also useful in staging the disease by showing the extent of the tumor spread to other organs.

Magnetic Resonance Imaging (MRI)

• Purpose: MRI scans are used to obtain highly detailed images of soft tissues and are particularly useful in assessing the extent of mesothelioma.
• What It Shows: MRI is often employed when more precise imaging of the diaphragm, chest wall, or other structures is needed. It can help determine whether the cancer has invaded surrounding tissues.

Positron Emission Tomography (PET) Scan

• Purpose: PET scans are often combined with CT scans (PET-CT) to provide a more comprehensive view of cancer activity in the body.
• What It Shows: PET scans detect areas of high metabolic activity, which often correspond to cancerous cells. This test is valuable for identifying metastasis and differentiating between benign and malignant growths.

Biopsy Procedures

While imaging tests can strongly suggest the presence of mesothelioma, a definitive diagnosis typically requires a biopsy, which involves taking a sample of tissue or fluid for examination under a microscope. Understanding how asbestos exposure leads to mesothelioma can provide context for why biopsies are necessary.

Needle Biopsy

A minimally invasive procedure used to obtain tissue samples from a suspected tumor or pleural effusion.

Types

• Fine-Needle Aspiration (FNA): A thin needle is inserted to extract cells or fluid for analysis.
• Core Needle Biopsy: A slightly larger needle is used to remove a small tissue sample, providing more information than FNA.

Thoracoscopy and Laparoscopy

• Purpose: These procedures allow for direct visualization and biopsy of the pleura (thoracoscopy) or peritoneum (laparoscopy).
• What It Involves: A small incision is made, and a thin, flexible tube with a camera (endoscope) is inserted into the chest or abdomen. This allows the surgeon to visually inspect the area and take tissue samples for biopsy.

Thoracentesis and Paracentesis

• Purpose: These procedures involve removing fluid from the pleural (thoracentesis) or abdominal cavity (paracentesis) for analysis.
• What It Involves: A needle is used to draw out the fluid, which is then examined for the presence of malignant cells. This is often used when there is significant fluid buildup, which is common in pleural and peritoneal mesothelioma.

Open Surgical Biopsy

• Purpose: In some cases, if less invasive methods do not provide a definitive diagnosis, an open surgical biopsy may be required.
• What It Involves: This procedure, performed under general anesthesia, allows for a larger tissue sample to be taken, which can provide more comprehensive diagnostic information.

Pathology and Laboratory Tests

Once a biopsy is performed, the tissue samples are analyzed by a pathologist to confirm the diagnosis of mesothelioma and determine its specific subtype. Understanding the causes of mesothelioma can aid in interpreting pathology results.

Histopathology

• Purpose: The study of the tissue structure and cell types in the biopsy sample.
• What It Shows: Pathologists examine the sample under a microscope to identify cancerous cells and determine whether the mesothelioma is epithelioid, sarcomatoid, or biphasic (a mix of both). This classification is crucial for guiding treatment decisions.

Immunohistochemistry

• Purpose: A laboratory test that uses antibodies to detect specific proteins in cells from the biopsy sample.
• What It Shows: Immunohistochemistry helps differentiate mesothelioma from other types of cancer or benign conditions by identifying markers specific to mesothelioma cells, such as calretinin, WT-1, and cytokeratin 5/6.

Blood Tests

Blood tests are not used to diagnose mesothelioma definitively but can support the diagnosis and monitor the disease. Recognizing common symptoms of mesothelioma can be helpful in conjunction with blood test results.

Types

• Mesothelin-Related Peptides (SMRP): Elevated levels of SMRP in the blood may indicate mesothelioma.
• Fibulin-3 and Osteopontin: These biomarkers are also being studied for their potential role in mesothelioma diagnosis and monitoring.

Staging and Further Testing

After confirming a mesothelioma diagnosis, staging tests are conducted to determine the extent of the disease and whether it has spread to other parts of the body. Accurate staging is essential for developing an appropriate treatment plan. Learn more about the stages of mesothelioma to understand how the disease progresses.

Lymph Node Biopsy

• Purpose: To check whether mesothelioma has spread to nearby lymph nodes.
• What It Involves: Lymph nodes are removed and examined to determine the presence of cancer cells.

Mediastinoscopy

• Purpose: A procedure used to examine and biopsy the lymph nodes in the chest.
• What It Involves: A small incision is made at the base of the neck, and a scope is inserted to access the lymph nodes in the mediastinum (the area between the lungs).

Additional Imaging Tests

• Purpose: Additional imaging, such as a bone scan or MRI of the brain, may be ordered if there is concern that mesothelioma has spread beyond the primary site.

Conclusion

Diagnosing mesothelioma involves a combination of imaging tests, biopsies, and laboratory analyses to confirm the presence of cancer, determine its type, and assess its spread. Early and accurate diagnosis is crucial for effective treatment and improved outcomes. For individuals at high risk, especially those with a history of asbestos exposure, awareness of these diagnostic tests and proactive medical evaluation can make a significant difference in managing the disease. Preventive measures against mesothelioma can also play a key role in reducing risk.

Sources:

• National Cancer Institute - Mesothelioma Detection and Diagnosis
• American Cancer Society - Tests for Mesothelioma
• Mayo Clinic - Mesothelioma Diagnosis
• Centers for Disease Control and Prevention (CDC) - Asbestos and Mesothelioma