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Last Modified April 21, 2022
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How Is Mesothelioma Diagnosed?

Depending on the patient’s symptoms, doctors will order different tests to narrow down the cause. In some cases, imaging tests for another illness may reveal mesothelioma. In other cases, a known history of asbestos exposure may require a tissue sample, known as a biopsy.

There is no clear path to a mesothelioma cancer diagnosis for every patient.

Providing your doctor with a comprehensive work history is essential to the diagnostic process. Doctors are unlikely to suspect the disease unless a patient describes a job where asbestos exposure may have occurred. Usually, mesothelioma symptoms develop 20 to 50 years after the initial asbestos exposure.

Doctors diagnose more than 3,000 cases of mesothelioma every year. However, because mesothelioma is a rare disease with similar symptoms to more common and less severe conditions, doctors sometimes confuse it for a different illness or another type of cancer.

Initial misdiagnosis is common for mesothelioma patients. Doctors often misdiagnose pleural mesothelioma as pneumonia or lung cancer. Peritoneal mesothelioma can appear similar to more common abdominal cancers. A mesothelioma specialist makes an accurate diagnosis by using imaging scans, biopsy results and other tests. 

What Steps Lead to a Mesothelioma Diagnosis?

Not every patient will need all these tests, but the process from symptoms to a final diagnosis is generally similar for most mesothelioma patients.

The symptoms of mesothelioma are vague, and seeking a diagnosis is often a multistep process. Coughing and shortness of breath are signs of pleural mesothelioma, while abdominal pain or digestive issues may signify peritoneal disease.

  1. Symptoms: Early symptoms of mesothelioma include cough, shortness of breath and chest or abdominal pain. Pleural patients will likely experience respiratory issues, but symptoms such as fatigue are common to any type of mesothelioma.
  2. Physical Exam: After patients report their symptoms to a physician, their doctor completes a physical exam to examine the heart, lungs and other vital organs. A detailed medical and work history also helps narrow down the possible cause of illness.
  3. Mesothelioma Testing: Radiology exams such as CT and PET scans of the chest or abdomen reveal disease location and size. With this information, doctors begin to develop a diagnosis and order further testing. They may also offer referrals to a surgeon or oncologist.
  4. Confirm Diagnosis: The imaging results from an MRI, CT or PET scan help surgeons plan for a biopsy to collect tissue and confirm a mesothelioma diagnosis and cell type. A blood test or radiology scan alone cannot establish a diagnosis of mesothelioma.

Patients with a known history of asbestos exposure are likely to receive a quicker referral to a mesothelioma specialist from the primary care physician. Accurately reporting your medical history, work history and symptoms to your doctor are essential in receiving mesothelioma tests that will lead to a diagnosis. 

General physicians and oncologists are responsible for confirming a diagnosis before starting treatment for a disease. Treatment for mesothelioma cannot begin until radiology and biopsy results have solidified an accurate diagnosis.

Advice for Recently Diagnosed Mesothelioma Cancer Patients

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

How to Test for Mesothelioma

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

If you have symptoms of mesothelioma, your doctor will conduct a physical exam to check for any unusual signs. Mesothelioma testing commonly includes imaging scans, such as MRI and CT scans, to identify malignant tumors. A biopsy, such as pleural aspiration or thoracoscopy, is the only definitive way to confirm a mesothelioma diagnosis.

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. 

During a physical exam, your provider may use specific tools or devices to look for signs of disease throughout the body.

  • Stethoscope: With a stethoscope, a physician listens to the sounds of the heart, lungs and abdomen. This test can identify specific signs of mesothelioma such as fluid buildup in the chest, known as a pleural effusion, or ascites in the abdomen.
  • Laryngoscopy: A slightly more invasive procedure involves using a tiny camera on a thin, flexible arm inserted through the nose or mouth to examine the throat and vocal folds. This procedure can rule out upper respiratory or throat cancers.
  • Stress Tests: Your doctor may examine your reflexes or ask you to perform light exercise to narrow your diagnosis for appropriate testing. Stress tests can help inform your provider if mesothelioma cancer is impacting your oxygen levels or heart rate.

Imaging Tests

Radiologists use imaging tests to reveal the location and size of mesothelioma tumors. 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. 

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. 


X-rays use radiation to produce basic images of areas within the body that show various densities, such as tumors or fluid. During an X-ray, the technician instructs the patient to hold a position and then takes several pictures. Contrast dye may or may not be involved.

Doctors use X-ray results to identify mesothelioma signs such as fluid buildup. This can include pleural effusion in the chest, pericardial effusion surrounding the heart or peritoneal effusion in the abdomen. 

CT Scans

Computerized axial tomography, or CAT scans, use computer software to integrate hundreds of fine X-ray images into highly defined pictures. These images of internal structures are much more precise than regular X-rays but also require more radiation. 

The process is like undergoing an X-ray but utilizes a much larger machine, and contrast may or may not be necessary for patients. The improved detail of a CT scan helps doctors identify smaller areas of tissue affected by cancer, making it easier to evaluate the cancer stage. 


Magnetic resonance imaging, or MRI, uses electromagnetic technology instead of radiation. MRIs generate precise images that are especially useful when looking at bone, nerve and brain tissue. This kind of scan helps doctors visualize which types of tissues are affected by mesothelioma and whether metastasis or spreading has occurred. 

The MRI patient lies on their back inside a narrow tube while a large magnet rotates inside the device. The process takes an average of 30 to 90 minutes, and contrast dye is optional. For patients with claustrophobia or anxiety, doctors may prescribe a one-time anti-anxiety medication. 


Positron emission tomography, or PET, involves an intravenous dose of a unique radioactive glucose dye, making inflamed cells light up during CT scans. As cells metabolize or eat the glucose due to infection or rapid growth, they cause inflammation, a sign of cancer that appears in detail on a PET-CT.

For the patient, the process is identical to a CT scan. For doctors, the improved contrast identifies areas within a tumor with the highest density of new growth. This information tells physicians how quickly the cancer is growing and where to target treatment. 

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Mesothelioma Blood Tests and Biomarkers

Some blood tests, such as MESOMARK and SOMAmer, can detect signs of mesothelioma. However, mesothelioma blood tests, biomarkers and immunohistochemical markers are not accurate enough to confirm a diagnosis alone. Doctors use these tests to rule out other disorders and monitor response to treatment.

Blood tests work by detecting mesothelin, a protein found in healthy patients, which circulates at higher blood levels when mesothelioma is present. For example, the FDA-approved MESOMARK test can detect soluble mesothelin-related peptides known as SMRPs. 

The SOMAmer test can detect more than 1,000 proteins in blood serum. These proteins may have diagnostic value in identifying mesothelioma. Another test known as Human MPF measures a protein called megakaryocyte potentiation factor. These tests have different rates of accuracy judged by sensitivity and specificity.

Diagnostic Capabilities of Mesothelioma Blood Tests
Test Sensitivity 1 Specificity 2
MESOMARK 68% 92%
SOMAmer 90% 95%
Human MPF 68% 95%
Source: 1. The percentage of mesothelioma patients correctly diagnosed by the test.
2. The percentage of healthy people in which the test correctly ruled out a mesothelioma diagnosis.

In testing, the SOMAmer mesothelioma blood test correctly diagnosed 90% of patients. This sensitivity is important because for a blood test to be practical, it must accurately predict disease reliably. 

Mesothelioma blood tests also undergo specificity testing. For example, MESOMARK accurately predicted that 92% of healthy patients did not have mesothelioma. Unfortunately, these results are not high enough for blood tests to definitively predict or diagnose mesothelioma. However, research is ongoing to develop blood tests with higher sensitivity and specificity. 

Mesothelioma Biopsies

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 most accurate biopsy technique for mesothelioma is called a thoracoscopy. The process differs for each type of biopsy, but doctors provide anesthesia to reduce pain. 

Approximately 98% of biopsies are definitive in diagnosing mesothelioma. The type of biopsy depends on cancer location and patient tolerance. Although less accurate, the surgeon may perform a fine needle aspiration or liquid biopsy, also known as a cytology test, for tumor tissue that is difficult to biopsy. 

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. For solid tissue samples, a 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.


Patients are under general anesthesia during a thoracoscopy. The surgeon inserts a small camera between the ribs to examine the appearance of the chest cavity. The scoped camera, called a thoracoscope, also suctions out excess fluid and collects small tissue samples as biopsies.

Thoracoscopies are the most accurate mesothelioma biopsy because they collect solid tissue samples directly from the primary tumor. Patients are asleep during the 45- to 90-minute procedure, and recovery takes about two weeks. The main risk with thoracoscopy is pneumonia. 


Doctors perform a mediastinoscopy to determine if cancer is present in the central chest region, called the mediastinum. The patient is under general anesthesia during the procedure. The surgeon inserts a tiny camera at the base of the neck to obtain biopsies of the lymph nodes around the windpipe. 

Like thoracoscopy, the scope device allows the surgeon to visually examine the area while removing excess fluid and collecting biopsy samples. Doctors use these samples to determine cancer stage based on the cancer’s extent within the lymph nodes. Greater lymph node involvement indicates a higher likelihood of metastasis. 


Thoracentesis requires only local anesthesia and is less invasive than thoracoscopy or mediastinoscopy. Doctors perform this procedure using an ultrasound probe for guidance, and the process takes roughly 15 minutes. 

The physician inserts a small needle between the ribs in the back or side to remove pleural fluid buildup around the lungs. Thoracentesis helps diagnose the cause of pleural effusions, but biopsy samples from this technique are of lower quality. 

Fine-Needle Aspiration

Like thoracentesis, fine-needle aspiration involves a small needle inserted between the ribs. However, compared to thoracentesis, the objective of FNA is to sample or biopsy tumors while the patient is in the CT scan machine.

While not as accurate as a solid tissue biopsy, FNA can rule out other illnesses and confirm a mesothelioma diagnosis along with positive radiology imaging such as a PET-CT scan. 

Endobronchial Ultrasound-Guided Biopsy

In a 2016 study, researchers used endobronchial ultrasound to guide biopsies and diagnose pleural mesothelioma when other biopsy techniques couldn’t obtain a tumor sample. This method uses a bronchoscope to examine the bronchi, the airways in the upper respiratory tract. 

Doctors combine transbronchial needle aspiration with endobronchial ultrasound to obtain tissue samples from the thoracic region. The process is similar to fine-needle aspiration, and the biopsies have a high level of diagnostic accuracy.

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How to Prepare for Mesothelioma Diagnostic Appointments

Preparing for a mesothelioma test such as a biopsy or imaging scan involves several steps, depending on the procedure. Your provider will detail dietary restrictions leading up to the day of your diagnostic appointment. 

You should also verify how and when to check your results. Some results, such as a mesothelioma biopsy, may take one to two weeks, whereas blood test results may be available immediately.

Preparing 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.
  • Take medications as usual, unless instructed otherwise.
  • Ask your doctor if your scan requires consuming liquid oral contrast before the scan and plan accordingly.
  • 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.
  • Plan to spend up to several hours at the appointment.
  • Ask your doctor how you’ll access your results. In most cases, your results will be available within a few days of the appointment.
Preparing for a 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.
  • Plan to spend about 30 minutes at the appointment.
Preparing for a Biopsy
  • Do not eat or drink anything six hours before your appointment.
  • Stop taking any blood-thinning medication at least five days before a biopsy.
  • Wear loose clothing to the appointment.
  • Have a designated driver take you home.
  • Plan to spend several hours undergoing the biopsy. Some biopsies, such as thoracoscopy, require at least a one-night stay in the hospital.

Timeline Leading Up to a Diagnosis

The diagnostic process is different for everyone depending on health status, asbestos exposure history and more. A potential diagnostic timeline can help explain how long it may take to receive a diagnosis after experiencing the first symptoms of mesothelioma.

Not everyone goes through the same diagnostic steps, or even in the same order. However, once you receive a mesothelioma diagnosis, this timeline can help you understand your treatment plan.

  • First Symptoms Appear
    Initial symptoms of pleural mesothelioma are commonly shortness of breath, fatigue and chest pain. These symptoms are similar to other conditions, such as pneumonia, heart failure or lung cancer, but they prompt your doctor to order testing.
  • Mesothelioma Testing Begins
    Tests for respiratory symptoms include X-rays to determine if there is fluid in the pleural cavity around the lungs, indicating pleural effusion. Your doctor will likely order these tests within a week of your initial symptoms.
  • Treatment to Rule Out Disease
    After a positive chest X-ray, your physician may prescribe an antibiotic to treat pneumonia or schedule a procedure within a week to drain fluid in the pleural cavity. Cancer cells may not be present in the liquid samples at this stage.
  • Follow-Up Evaluation
    Within a month of your initial symptoms and treatment, your doctor will likely order repeat X-rays to confirm the lungs are clear. If the fluid has returned, the provider may repeat the same treatment before ordering more thorough tests such as PET and CT scans.
  • Imaging Results
    Roughly two months after your first doctor appointment, the results of your imaging scans may show an abnormal mass causing fluid accumulation or recurrent pneumonia. At this point you may receive a surgical referral, which can take up to 15 days.
  • Surgical Biopsy
    About two weeks after your imaging results, a surgeon may schedule a biopsy appointment for video-assisted thoracoscopic surgery. This procedure often requires a hospital stay of one to three days. The results of the biopsy, also known as pathology, can take up to 10 days.
  • Mesothelioma Diagnosis
    After reviewing the biopsy results and previous imaging scans, your doctor may have enough information to confirm a mesothelioma diagnosis, roughly three months from your initial symptoms. A mesothelioma specialist can help you plan the next steps.
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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 treating the disease. 

Asbestos-related diseases such as mesothelioma take an average of 20 years to develop, and symptoms often mimic many other more common illnesses. In most cases, only a specialist 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, cardiac issues, abdominal cancer or an infectious disease such as pneumonia. Peritoneal mesothelioma misdiagnosis may also include irritable bowel syndrome, ovarian cancer or colon cancer. 

In a 2012 study published in the Journal of Thoracic Oncology, researchers examined the rates of mesothelioma misdiagnosis across 1,056 patients. Misdiagnosis occurred in almost 50% of mesothelioma patients. More than 80% of patients with stage 1 mesothelioma received an incorrect initial diagnosis before a doctor later diagnosed them correctly at a more advanced stage. 

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 for a patient.

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 determine a mesothelioma patient’s life expectancy.

  • Clinical staging uses imaging scans and biopsies to estimate the stage. Imaging tests, particularly PET scans, are the best noninvasive tools doctors have for assessing the mesothelioma clinical stage.
  • Surgical staging procedures such as thoracoscopy and mediastinoscopy are more invasive and involve minor surgery. They help determine with more precision the extent of cancer and if tumors have spread beyond the pleural lining or into lymph nodes.

During clinical staging, if the CT scan or PET scan reveals tumor spread to other organs, also known as late-stage mesothelioma or metastatic disease, the provider 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 realize they are sick unless they have a clear history of asbestos exposure.

Patients may forget or not mention their history of asbestos exposure. Consequently, their doctor might not consider mesothelioma as a possible diagnosis. This miscommunication may contribute to a delay in diagnosis, allowing cancer to progress without proper treatment.


When a doctor delivers a mesothelioma diagnosis, they might also describe the patient’s prognosis. A prognosis is a description of the patient’s likely response to treatment. Some doctors may hypothesize prognosis after the initial diagnosis, while others may wait to assess the patient’s response to the first course of therapy.

It is challenging for doctors to accurately predict mesothelioma’s course in a patient’s body because each case is unique. Doctors base their prognosis on the mesothelioma stage, location and cell type, plus the patient’s age and overall health.

Steps to Take After a Mesothelioma Diagnosis

After a mesothelioma diagnosis, the patient can begin treatment to help extend life expectancy and improve survival. Seeking a mesothelioma specialist ensures access to advanced treatment options and resources. 

Patients diagnosed with mesothelioma may find it difficult to come to terms with their illness. A robust support system is essential for understanding your treatment course and options for palliative care, hospice and other services. 

Seek a Second Opinion

If you’ve been diagnosed with mesothelioma by a general oncologist or other practitioner, the recommended next step is seeking 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. Doctors and cancer centers specializing in mesothelioma provide access to innovative therapies and clinical trials.

Create a Treatment Plan

Another essential step is thoroughly understanding your treatment plan. This strategy is something you can discuss in detail with your oncologist. If any aspect of your mesothelioma treatment plan makes you nervous or confused, talk to your doctor about it.

Mesothelioma specialists understand the connection between diagnosis, staging and treatment options such as early-stage surgery or clinical trials for metastatic disease. Ask about palliative care and complementary therapies that may help with side effects. For example, massage and acupressure may help with chemotherapy-induced nausea.

Find Support

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.

The Mesothelioma Center provides a monthly online support group for patients, families and caregivers to share their experiences and help each other cope with their diagnosis.

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 biopsy.

Can a chest X-ray show mesothelioma?

Physicians use X-rays to visualize fluid or masses within the body. These images can depict large tumors in the chest or fluid buildup in the pleura but are not used to diagnose mesothelioma. Mesothelioma specialists order advanced imaging, such as a PET-CT scan, along with a biopsy to confirm diagnosis.

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. Mesothelioma latency, the period after asbestos exposure and before initial symptoms develop, is about 20-50 years.

What should I do after a mesothelioma diagnosis?

After a physician has confirmed your diagnosis, the next step is working with your health care team to develop a mesothelioma treatment plan. Cancer treatment is expensive, and experts recommend patients begin financial planning early in their treatment. A mesothelioma lawyer can help you get asbestos compensation to pay for the cost of cancer treatment.

Could I be tested for mesothelioma during the COVID-19 pandemic?

Yes, if you have a history of asbestos exposure and are experiencing signs of asbestos-related diseases, a mesothelioma specialist can accurately test for these illnesses during the COVID-19 pandemic. Receiving an early and accurate mesothelioma diagnosis can ensure you gain access to a more significant number of available treatment options.

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