Written By: Karen Selby, RN,
Last modified: May 24, 2021

How Mesothelioma Is Diagnosed

There is no clear path to a mesothelioma cancer diagnosis for every patient. Depending on the patient’s first 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.

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.

  1. Symptoms: Symptoms of mesothelioma cause the patient to visit their primary care physician or a hospital for testing. The initial symptoms of the disease may differ for each patient and range from cough to general pain or more severe issues.
  2. Physical Exam: A physician takes a medical history and completes a physical exam to narrow down possible causes of illness. The exam may include visual inspection of the lungs with a scoped instrument, listening to the heart and lungs with a stethoscope, or physical tests such as light exercise or reflex reactions.
  3. Mesothelioma Testing: The most common first tests are radiology exams such as chest X-rays and CT scans of the chest or abdomen. These initial tests reveal abnormal results with information such as disease location and size. With this information, doctors order further testing and may offer referrals to a surgeon or oncologist.
  4. Confirm Diagnosis: The surgeon or oncologist uses a combination of imaging scans, blood tests and biopsies to establish a mesothelioma diagnosis. A blood test or radiology scan alone cannot confirm a diagnosis of mesothelioma. Doctors typically obtain tissue sample biopsies from surgery.

Because mesothelioma is a rare disease and has 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 as more common abdominal cancers.

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.

Researchers are working on ways to detect mesothelioma earlier and with less-invasive tools. According to a 2020 review authored by mesothelioma expert Dr. Harvey Pass and others, the potential to diagnose the rare disease with a breath test might one day be a reality.

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

Testing for Mesothelioma

Mesothelioma testing commonly includes imaging scans, biopsies and blood tests. Imaging scans such as X-rays and CT scans identify mesothelioma tumors. A biopsy is the only definitive way to confirm a mesothelioma diagnosis. Doctors also use mesothelioma blood tests to measure treatment response.

Imaging Tests

Imaging tests performed by radiologists reveal the location and size of mesothelioma tumors. These scans also 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 produce basic images of areas with various densities, such as tumors or fluid, within the body.
  • CT Scans: Computerized Axial Tomography or CAT scans use computer software to integrate hundreds of fine X-ray images to create detailed images of internal structures. These images are much more precise than regular X-rays.
  • MRIs: Magnetic Resonance Imaging uses electromagnetic technology instead of radiation. MRIs generate precise images, which are especially useful when looking at bone, nerve and brain tissue.
  • PET-CT: Positron Emission Tomography involves an intravenous dose of radioactive glucose, making inflamed cells light up during CT scans. Infection or rapid growth may cause cell inflammation, a sign of cancer that appears in detail on a PET-CT.

Mesothelioma Biopsies

Biopsies are the only way to confirm a mesothelioma diagnosis. The most accurate biopsy technique for mesothelioma is called a thoracoscopy.

Quick Fact:
98% of biopsies are definitive in diagnosing mesothelioma.
Source: Macmillan Mesothelioma Network, 2021
  • Thoracoscopy: While under general anesthesia, the surgeon inserts a small camera between the ribs to suction out the fluid, examine the appearance of the inside of the chest and take biopsies.
  • Mediastinoscopy: Also under general anesthesia, the surgeon inserts a small camera at the base of the neck to obtain biopsies of the lymph nodes around the windpipe.
  • Thoracentesis: Under local anesthesia and usually using an ultrasound probe, a small needle is inserted between the ribs in the back to remove pleural fluid buildup around the lungs. It is used to diagnose the cause of pleural effusions.
  • Fine-Needle Aspiration: Under local anesthesia, a small needle is inserted between the ribs to sample or biopsy tumors while the patient is in the CT scan machine.
  • Endobronchial Ultrasound-Guided Biopsy: According to a 2016 study, this type of biopsy is helpful at diagnosing pleural mesothelioma when other biopsy techniques can’t obtain a tumor sample.

Mesothelioma Blood Tests and Biomarkers

Mesothelioma blood tests, biomarkers and immunohistochemical markers are not accurate enough to diagnose the cancer alone. They are helpful at monitoring response to treatment. 

  • MESOMARK: This FDA-approved test can detect soluble mesothelin-related peptides known as SMRPs.
  • SOMAmer: This test can detect more than 1,000 proteins in blood serum. These proteins may have diagnostic value in identifying mesothelioma.
  • Human MPF: This test measures a protein called megakaryocyte potentiation factor.
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.
2020 Mesothelioma Packet from the Mesothelioma Center
Free Mesothelioma Guide
Learn more about mesothelioma in our comprehensive guide. Over 200+ pages covering treatment options, support, and more.

Challenges in Diagnosing Mesothelioma

Staging Mesothelioma

Staging mesothelioma is an important but challenging part of the diagnostic process. Staging defines how far the cancer has progressed, which is the biggest factor in determining which treatments are right for a patient.

Cancer stage is also a primary factor influencing a mesothelioma patient’s life expectancy.

  • Clinical staging uses imaging scans and biopsies to estimate the stage. Imaging tests, and in particular PET scans, are the best noninvasive tools doctors have for estimating the stage of mesothelioma. If the CT scan or PET scan reveals tumor spread to other organs, also known as late-stage mesothelioma or metastatic disease, a needle biopsy can be performed to prove this spread.
  • Surgical staging procedures such as a thoracoscopy and mediastinoscopy are minimally invasive, and they can help determine with more precision the extent of the cancer and if the cancer has spread beyond the pleural lining or into lymph nodes.


Sometimes mesothelioma is misdiagnosed as a less serious disease or another cancer. The initial symptoms of mesothelioma can resemble other conditions.

  • Pleural mesothelioma symptoms may lead to a diagnosis of pneumonia or heart failure.
  • Peritoneal mesothelioma symptoms may lead to a diagnosis of irritable bowel syndrome.
  • Pericardial mesothelioma symptoms may lead to a diagnosis of coronary heart disease.
I personally believe that, had it not been for [Karen’s] help, we might never have found out dad’s true diagnosis of mesothelioma.
Sherry P.

Doctors may also misdiagnose mesothelioma as other forms of cancer.

  • Pleural mesothelioma may be misdiagnosed as a form of lung cancer called adenocarcinoma that develops in mucus-secreting glands.
  • Peritoneal mesothelioma may be misdiagnosed as ovarian cancer or colon cancer.
Quick Fact:
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 if it is cancerous.

Working with a nationally recognized cancer center that specializes in mesothelioma can confirm or deny the diagnosis. The doctors at these cancer centers have the experience necessary to diagnose this rare disease accurately.

Lorraine Kember video on coping with mesothelioma loss

Watch: Lorraine Kember, a former mesothelioma caregiver, describes how she felt when her husband tested positive for mesothelioma.

Latency Period

The decades-long latency period associated with asbestos-related diseases means it takes decades before patients experience symptoms. In that time, some patients forget they were exposed to asbestos a long time ago.

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 offer this information freely, while others may wait for the patient to ask.

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

How to Prepare for Mesothelioma Diagnostic Appointments

  • Assemble all necessary documents, including insurance cards and ID.
  • Make sure to discuss any asbestos exposure you may have experienced, including length, time and location of exposure.
  • Bring a summary of your medical history, including details about your recent symptoms and a list of current medications.
  • Bring something to take notes with during the appointment.
  • Gather a list of questions you have for your medical team.
  • Ask a friend or family member to join you for support and assistance.
An older woman undergoing a CT-PET scan, a common tool in mesothelioma testing
Imaging tests, like a PET scan, can reveal tumors and are regularly used to test for mesothelioma.

How to 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. But 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.
  • 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.

How to Prepare 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 types of biopsies, such as a thoracoscopy, require at least a one-night stay in the hospital.
  • You may have to wait one to two weeks to get the results.

How to Prepare for a Blood Test

  • Ask how long you must fast before the blood test. Some tests require you to not eat after midnight the night before your appointment.
  • Book an early-morning appointment if you have to fast for the test.
  • Drink plenty of water, which prevents your blood pressure from dropping.
  • Plan to spend about 30 minutes at the appointment.

Depending upon the test, you may receive results instantly or within a week.

Timeline of the Diagnostic Process for Mesothelioma

The following schedule is an example of how a typical mesothelioma patient may go through the procedures leading to their diagnosis. While this process is different for everyone, this timeline can help explain how long it may take to receive a diagnosis after experiencing the first symptoms of mesothelioma.

Day 1:

Initial symptoms, such as shortness of breath, fatigue and chest pain, are common. Although these symptoms are similar to more common conditions, such as pneumonia, heart failure or lung cancer, they will trigger your doctor to order X-rays or scans.

Day 2:

X-rays determine if there is fluid in the pleural cavity around the lungs which could be pneumonia.

Day 3-Day 13:

Physician prescribes antibiotic to treat pneumonia (10-day treatment) or drains fluid in pleural cavity. No cancer cells detected in fluid.

Day 14:

X-rays after treatment show lungs are clear. Doctor orders follow-up X-rays and asks patient to return in 30 days.

Day 44:

Follow-up X-rays show fluid buildup in pleural cavity again. Doctor either drains fluid, which may again test negative for cancer cells, or treats the pneumonia with antibiotics again (add 10 days). Doctor orders PET scans and CT scans.

Day 54:

Imaging scans show a possible underlying cause or recurrent pneumonia. Patient is referred to a surgeon for an appointment, which can take up to 15 days.

Day 69:

Surgeon schedules a biopsy appointment, which can take up to 10 days.

Day 79:

Surgeon takes biopsy, usually with video-assisted thoracoscopic surgery. While under general anesthesia, the surgeon inserts a small camera between the ribs to suction out the fluid, examine the appearance of the inside of the chest and take biopsies. This typically requires a hospital stay of 1-3 days. The results of the biopsies, also known as pathology, can take up to 10 days.

Day 89:

(Approximately three months later): Mesothelioma confirmed if biopsy tests positive for the disease.

Mesothelioma specialist speaking with a patient and his wife
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Steps to Take After a Mesothelioma Diagnosis

Seek a Second Opinion

The next step after a mesothelioma diagnosis for many people is seeking a second opinion from a mesothelioma specialist. Choosing a doctor and cancer center specializing in mesothelioma can confirm the diagnosis and get you access to innovative therapies and clinical trials.

Understand Your Treatment Plan

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

Ask about palliative care and complementary therapies that may help with side effects. For example, massage and acupressure may help with chemotherapy-induced nausea.

Get Support

Lastly, 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 a being diagnosed with mesothelioma.

Common Questions About Diagnosing 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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