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Last Modified September 20, 2022
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How Is Mesothelioma Diagnosed?

Mesothelioma is primarily diagnosed with imaging scans and tissue samples known as biopsies. Tests like these complement blood tests, physical exams and patient histories regarding health and asbestos exposure.

Mesothelioma is difficult to diagnose because it is a rare disease with symptoms similar to more common and less severe conditions. Doctors initially misdiagnose many of the approximately 3,000 cases found annually 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 and see your doctor if you develop symptoms involving your lungs or digestive system. These actions may lead to an early diagnosis, which is associated with longer survival because treatments are more effective.

What Steps Lead to a Mesothelioma Diagnosis?

The diagnostic process is different for everyone depending on health status, asbestos exposure history and more. Doctors perform a physical exam and look for the symptoms of mesothelioma before ordering additional tests.

Not everyone goes through the same diagnostic steps, or even in the same order.

  • 1-2 weeks First Doctor Visit
    Doctor visit icon Review medical history, discuss symptoms and note possible asbestos exposure.
  • 1-2 weeks Imaging Scans
    X-rays Icon Typically X-Rays are taken, and PET and CT scans may be ordered.
  • 1-2 weeks Review Results
    Review test results icon Images are reviewed and if abnormalities are detected, for example, an abnormal mass, a surgical referral may be given.
  • 2-4 weeks Surgical Biopsy
    Surgical Biopsy icon Video-assisted thoracoscopic surgery often requires a hospital stay of one to three days. Biopsy results can take up to 10 days.
  • 2 weeks Mesothelioma Diagnosis
    Doctor confirms the results Icon After reviewing biopsy results and previous scans, your doctor may be able to confirm your diagnosis.
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How to Test for Mesothelioma

The first step toward getting tested and diagnosed for mesothelioma involves speaking with your primary care doctor about your symptoms, health history and asbestos exposure.

If you have symptoms of mesothelioma, your doctor will conduct a physical exam of your body to check for any unusual signs. Testing for mesothelioma commonly 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.

Doctors also use mesothelioma blood tests to measure treatment response.

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

Physical Exam and Medical History

Mesothelioma is rare and difficult to diagnose. The more details your doctor has about your medical history, symptoms and asbestos exposure, the more informed they will be when ordering mesothelioma tests.

Doctors may use specific tools or devices during a physical exam to look for signs of disease throughout the body, including your chest and abdomen.

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: 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, or CAT scans, use computer software to integrate hundreds of fine X-ray images into highly defined pictures.
  • MRIs: Magnetic resonance imaging, or MRI, uses electromagnetic technology instead of radiation. MRIs help doctors visualize which types of tissues are affected by mesothelioma and 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 monitor response to treatment.

  • MESOMARK: The FDA-approved MESOMARK test can detect soluble mesothelin-related peptides. Mesothelin, a protein found in healthy patients, circulates at higher blood levels when mesothelioma is present.
  • SOMAmer: 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, or correctly detecting a disease, and specificity, or identifying 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 definitively predict or diagnose mesothelioma. These tests cannot replace a biopsy’s pathology report that gives the official diagnosis using immunohistochemical testing and other pathology techniques. However, 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.

  • Thoracoscopy: 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. 
  • Mediastinoscopy: This test takes tissue samples of the lymph nodes around the windpipe, which can help to diagnose the stage of pleural mesothelioma.
  • Laparoscopy: A laparoscopy is used to examine the abdominal cavity and collect tissue samples in patients suspected of having peritoneal mesothelioma.

Although less accurate, a radiologist may perform a fine needle aspiration or liquid biopsy, also known as a cytology test, for tumor tissue that 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

If you’ve been diagnosed with mesothelioma by a general oncologist or other 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 and access to all available treatment options. 

Mesothelioma specialists and experienced treatment centers will review your medical history, blood tests, imaging and biopsies to confirm your diagnosis and begin a personalized treatment plan. This plan may include surgery, chemotherapy, radiation therapy or immunotherapy.

Doctors and cancer centers specializing in mesothelioma provide access to innovative therapies and clinical trials. If initial treatment doesn’t control the cancer, 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.

Peritoneal mesothelioma survivor shares advice when diagnosed with mesothelioma

Watch: Mesothelioma survivor Tamron Little shares her advice for people recently diagnosed with mesothelioma.

Why Is Diagnosing Mesothelioma Challenging?

Mesothelioma is a rare and complex disease. Diagnosing mesothelioma is challenging because many general practitioners and oncologists never encounter it or know the intricacies of detecting the disease.

Mesothelioma symptoms often mimic more common illnesses. Doctors specializing in mesothelioma can 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, cardiac problems, abdominal cancer or an infectious disease such as pneumonia. Peritoneal mesothelioma misdiagnoses may also include irritable bowel syndrome, ovarian cancer or colon cancer. 

Documenting asbestos exposure history and working with a nationally recognized cancer center specializing in mesothelioma is essential to confirming a diagnosis. The specialists at these cancer centers have the experience necessary to diagnose this rare disease accurately.

Staging Mesothelioma

Staging mesothelioma is a necessary but challenging part of the diagnostic process. Staging 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 tumor spread 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 associated with 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 remeber 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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