How Is Mesothelioma Diagnosed?

Imaging scans and tissue samples known as biopsies help to diagnose mesothelioma. Other tests include blood tests and physical exams. Patient histories of health and asbestos exposure also play a role.

Mesothelioma cancer is difficult to diagnose. It is a rare disease with symptoms like more common and less severe conditions. Doctors often misdiagnose it. Each year, about 3,000 cases occur in the U.S. The average age of patients receiving a mesothelioma diagnosis is 72.

If you have a history of asbestos exposure, it is important to seek cancer screenings. See your doctor if you develop symptoms involving your lungs or digestive system. These actions may lead to an early diagnosis. Longer survival is possible with an early diagnosis because treatments are more effective.

What Steps Lead to a Mesothelioma Diagnosis?

The first step is typically a physical exam. You and your doctor will discuss your medical history and any history of asbestos exposure that could put you at risk for asbestos-related diseases. Based on your exposure history, your doctor will look for symptoms of mesothelioma.

The diagnostic steps depend on health status, asbestos exposure history and more. The process is different for everyone. Not everyone goes through the same diagnostic steps, or even in the same order.

Process of how mesothelioma is diagnosed
Accurately diagnosing malignant mesothelioma takes several steps and involves a variety of tests.

Depending on the results of your initial exam, your doctor will likely order more tests. These include blood tests and biopsies. For mesothelioma, actual tissue from tumors is usually obtained through a thoracoscopy — a type of biopsy that is 98% accurate at diagnosing the cancer.

How to Test for Mesothelioma

Testing for mesothelioma includes imaging scans, such as MRI and CT scans, to identify malignant tumors. A biopsy is the only definitive way to confirm a mesothelioma diagnosis. Biopsy procedures can include pleural aspiration and a thoracoscopy.

Pathologists are doctors who examine tissue samples from a biopsy under a microscope. This process is known as histology. A subspecialty of histology known as immunohistochemistry uses special stains to reveal more details about a tumor that helps doctors treat it more efficiently.

Medical History and Physical Exam

A doctor will review your medical history, symptoms and asbestos exposure. This information will help when ordering mesothelioma tests.

Doctors may use specific tools or devices during a physical exam to look for signs of disease. They will examine your chest and abdomen for signs of pain or tumors.

Imaging Tests

Radiologists use imaging tests to reveal the location and size of mesothelioma tumors around the lungs or abdomen. These scans are precise and detailed enough to determine the extent and stage of cancer, such as whether it has entered lymph nodes or other organs.

The “gold standard” for mesothelioma imaging is a combination PET-CT scan with contrast dye.


X-rays use radiation to produce basic images of areas within the body that show various densities, such as tumors or fluid.

CT Scans

Computerized axial tomography uses computer software. The software integrates hundreds of fine X-ray images into defined pictures.


Magnetic resonance imaging, or MRI, uses electromagnetic technology instead of radiation. MRIs help doctors visualize which types of tissues contain mesothelioma. It also shows whether metastasis or spreading has occurred.

Scans that use contrast dye, such as PET or MRI, involve oral contrast that the patient drinks before the exam or IV contrast injected through a vein.

Imaging tests are painless, and many take only minutes. An MRI can take 30 to 90 minutes and may cause anxiety in some patients due to the small space and loud noise. Anti-anxiety medications may be prescribed to help patients relax during the scan.

Blood Tests and Biomarkers

Mesothelioma blood tests are not accurate enough to confirm a diagnosis alone.

These blood tests, such as MESOMARK and SOMAmer, can detect biomarkers of mesothelioma. Doctors use these tests to rule out other disorders and watch responses to treatment.


The FDA-approved MESOMARK test can detect soluble mesothelin-related peptides. Mesothelin is a protein found in healthy patients. It circulates at higher blood levels when mesothelioma is present.


The SOMAmer test can detect more than 1,000 proteins in blood serum. These proteins may have diagnostic value in identifying mesothelioma.

Human MPF

Human MPF measures a protein called megakaryocyte potentiation factor.

These tests have different rates of accuracy judged by sensitivity and specificity. Sensitivity detects a disease when it is present. Specificity detects when the disease is not present.

For example, MESOMARK accurately predicted that 92% of healthy patients did not have mesothelioma. In testing, the SOMAmer mesothelioma blood test correctly diagnosed 90% of patients.

Unfortunately, these results are not high enough for blood tests to predict or diagnose mesothelioma. These tests cannot replace a biopsy’s pathology report that gives the official diagnosis. Biopsies use immunohistochemical testing and other pathology techniques. Research is ongoing to develop blood tests with higher sensitivity and specificity.

Biopsy Procedures

Biopsies are the only way to confirm a mesothelioma diagnosis. These tissue samples inform doctors of cancer cell type and stage, helping them develop a more precise treatment plan. 

The type of biopsy depends on cancer location and patient tolerance. The process differs for each type of mesothelioma biopsy, but doctors provide anesthesia to reduce pain.


This is the most accurate biopsy technique for mesothelioma. It can accurately detect 98% of mesothelioma cases.  

Cytology Test

In a cytology test, the doctor removes fluid from the suspected tumor site. A pathologist then looks at the liquid under a microscope to search for cancer cells. 


This test takes tissue samples of the lymph nodes around the windpipe. The test can help diagnose the stage of pleural mesothelioma.


A laparoscopy is used to examine the abdominal cavity. It collects tissue samples in patients suspected of having peritoneal mesothelioma.

A radiologist may perform a fine needle aspiration or liquid biopsy. It is also known as a cytology test. Although less accurate, it is helps when tumor tissue is difficult to biopsy.

For solid tissue samples, the doctor removes a piece of the suspected tumor during a biopsy. Then, a pathologist looks at it under a microscope to determine cancer cell type and characteristics.

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Getting Treatment Following a Mesothelioma Diagnosis

Treatment for mesothelioma may include surgery, chemotherapy, radiation therapy or immunotherapy. A mesothelioma specialist has the best expertise to oversee your care plan.

Were you diagnosed with mesothelioma by a general oncologist or another practitioner? The recommended next step is to seek a second opinion from a mesothelioma specialist. A second opinion is essential to ensure you have received the correct diagnosis. 

Mesothelioma specialists at experienced treatment centers will review your case. This includes medical history, blood tests, imaging and biopsies. They will confirm your diagnosis and begin a personalized treatment plan.

Doctors specializing in mesothelioma provide access to innovative therapies and clinical trials. You may consider different treatments available through clinical trials. 

Build a mesothelioma support network to help you and your loved ones cope with this cancer. Reach out to family, friends, neighbors and community members. A strong support system will help you get through the challenges of being diagnosed with mesothelioma.

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Why Is Diagnosing Mesothelioma Challenging?

Diagnosing mesothelioma is challenging because many general practitioners and oncologists never encounter it. Mesothelioma is a rare and complex cancer. General doctors don’t know the intricacies of detecting the disease.

Mesothelioma symptoms often mimic more common illnesses. Specialists provide an early mesothelioma diagnosis, timely treatment and an improved prognosis.


Sometimes mesothelioma is misdiagnosed as a less severe disease or another cancer. The initial symptoms of mesothelioma can resemble lung cancer and other chest issues. These issues include cardiac problems, abdominal cancer or an infectious disease such as pneumonia.

Peritoneal mesothelioma misdiagnoses also occur. Examples include irritable bowel syndrome, ovarian cancer or colon cancer. 

A recognized cancer center specializing in mesothelioma can confirm a diagnosis. The specialists at these centers have the expertise to diagnose this rare disease.

Staging Mesothelioma

Staging mesothelioma defines how far cancer has progressed, which is the most significant factor in determining what treatments are suitable.

Clinical staging relies on the patient’s symptoms, physical exam and radiology findings to determine a preliminary stage. Surgical staging requires solid tissue samples but provides a definitive diagnosis.

Staging also helps forecast a mesothelioma patient’s life expectancy. During clinical staging, if the CT scan or PET scan reveals tumors spreading to other organs, also known as stage 4 or metastatic disease, a doctor can perform a needle biopsy to prove this diagnosis.

Latency Period

The long latency period of asbestos-related diseases means it takes decades before patients experience symptoms. This extended period makes early diagnosis difficult since patients may not think to mention asbestos to their doctor because they do not remember the exposure.

As a result, their doctor might not consider mesothelioma a possible diagnosis. This miscommunication may contribute to a late-stage mesothelioma diagnosis, allowing cancer to progress without proper treatment.

Common Questions About Mesothelioma

Is mesothelioma difficult to diagnose?

Mesothelioma is one of the most challenging cancers to diagnose. Misdiagnosis is common because symptoms are similar to several common illnesses, and many doctors have never seen the rare disease. In many cases, a mesothelioma doctor confirms diagnosis through the use of a test called a biopsy.

How long does it take to diagnose mesothelioma?

The average time from initial symptoms, such as shortness of breath or chest pain, to a mesothelioma diagnosis is approximately three months.

How do you prepare for a diagnostic imaging scan?

You may have a light meal or snack four hours before the scan, then no food or drink by mouth. However, some scans, such as a PET-CT scan, require eight hours of fasting. Research relaxation techniques if you are nervous about being in an enclosed scanning machine or inform your provider you may have anxiety on the exam day.

How do you prepare for a mesothelioma blood test?

Ask how long you must fast before the blood test. Some tests require you not to eat after midnight the night before your appointment. Book an early morning appointment if you must fast for the test. Drink plenty of water, which prevents your blood pressure from dropping.

How do you prepare for a mesothelioma biopsy?

Stop taking any blood-thinning medication at least five days before a biopsy. Wear loose clothing to the appointment, and plan to have a designated driver take you home. Do not eat or drink anything six hours before your appointment. Plan to spend several hours undergoing the biopsy. Some biopsies, such as thoracoscopy, require at least a one-night stay in the hospital.

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