Mesothelioma Diagnosis

Mesothelioma diagnosis usually involves taking imaging scans of tumors, recording the patient’s history of asbestos exposure, and analyzing a biopsy of cancer tissue. This rare disease can be mistaken for an infection or a more common type of cancer, so diagnosing it requires a specialist.

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How Is Mesothelioma Diagnosed?

Diagnostic Procedures to Test for Mesothelioma

  • Imaging tests such as MRIs, CT scans, PET scans and X-rays

  • Biopsies to investigate cancerous growth in tissue samples

  • Blood marker tests used so doctors can examine blood to determine if cancer is present and what type

There is no clear path to a mesothelioma cancer diagnosis for every patient. Because the disease is rare and has such common symptoms, doctors sometimes confuse it for a less serious illness or a different type of cancer.

The most common presenting symptoms of pleural mesothelioma include chest pain and difficulty breathing. Peritoneal mesothelioma patients typically experience abdominal pain and distension. Anyone with a history of occupational asbestos exposure should remain watchful for these symptoms. Report them to a doctor immediately.

Important Facts about Mesothelioma Diagnosis

  • Only a biopsy can confirm a mesothelioma diagnosis.

  • Imaging scans and blood tests help to identify and monitor the cancer.

  • Early-stage diagnosis leads to more treatment options and longer life span.

Pinpointing the disease involves several procedures. These may include X-rays, CT scans, MRIs, PET scans and biopsies. Each of these tests is performed by a different medical professional. Most people get their diagnosis within two or three months from the time they notice their symptoms.

Diagnosing the cancer in its earliest stages affords a wider range of treatment possibilities that could extend your life expectancy. It’s important that you find an expert who understands the different mesothelioma stages and can provide you the best treatment.

What Steps Lead to a Mesothelioma Diagnosis?

There are three steps to the mesothelioma diagnosis:

  1. Symptoms Begin to Show: Patient detects symptoms of mesothelioma, which often mimic those of other diseases. Symptoms develop when the cancer reaches later stages of progression, usually stage 3 or 4.

  2. Patient Consults Primary Care Physician: The primary care physician discusses symptoms with patient. These doctors perform preliminary tests. If cancer is suspected, they refer patient to an oncologist.

  3. Oncologist Makes Final Diagnosis: The oncologist conducts a variety of tests based on the patient’s health. Tests may include imaging scans, blood tests and biopsies to confirm a mesothelioma diagnosis.

Doctors start the diagnostic process by asking about your medical history and by performing some standard physical exams. They should ask if you recall any personal past exposure to asbestos.

Providing your doctor with a comprehensive work history is important to the diagnostic process. Mesothelioma is a rare cancer with nonspecific symptoms. Doctors are unlikely to suspect the disease unless a patient describes a former job where asbestos exposure may have occurred.

Next, doctors will order imaging tests to identify any abnormal growths. If those show a suspicious mass that looks like mesothelioma, doctors will request a biopsy to confirm the diagnosis. They will take fluid and tissue samples during the biopsy.

During this process, you’ll see several doctors. Patients usually visit a general practitioner, pulmonologist, radiologist, surgeon, pathologist and an oncologist. If any of these doctors suspect mesothelioma or another asbestos disease, that’s a sign for any patient to get a second opinion from a mesothelioma specialist, an expert who has experience staging the cancer and treating people who have it.

The doctors who specialize in mesothelioma have dedicated the time it takes to understand the intricacies of diagnosing and treating this disease. They’ve studied under other mesothelioma experts, conducted clinical research and overseen clinical trials. They’ve also worked with more mesothelioma patients than the average cancer doctor.

The cancer centers that specialize in mesothelioma staff a team of doctors who are experts in subspecialties of mesothelioma diagnosis and treatment. These subspecialties include pathological, surgical and radiological oncology. The pathologists at these centers have more experience diagnosing mesothelioma than most throughout the U.S. These doctors learn from each other. They work together to provide each patient with individualized treatment.

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Timeline for Diagnosing Mesothelioma

The timeline for diagnosing mesothelioma varies from patient to patient. It’s based on the symptoms, doctor’s experience with the illness, types of tests required to confirm the disease and wait times for the results of those tests.

Timeline of the Diagnostic Process for Mesothelioma

Day 1:
Initial symptoms such as shortness of breath, fatigue and chest pain are common. It’s usually not diagnosed at that time, but the doctor might order X-rays.
Day 2:
X-rays determine fluid in the lungs 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 done via VATS (a procedure that uses a thin fiber-optic tube to enter the chest cavity and take biopsy samples). This typically requires a three-day hospital stay for the patient. Lab work to confirm mesothelioma can take up to 10 days if surgeon sends biopsy to an outside lab.
Day 89:
(Approximately three months later): Mesothelioma confirmed if biopsy tests positive for the disease.
Sherry P.

“I personally believe that, had it not been for [Karen’s] help, we might never have found out dad’s true diagnosis of mesothelioma.”

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Preparing for Mesothelioma Diagnostic Appointments

Most patients make an appointment with their general physician several weeks or months after they first notice something wrong with their health. They might be experiencing abdominal or chest pain. Other times they have an unexplained acute shortness of breath or have trouble catching their breath after light exertion.

How to prepare for a diagnostic imaging scan:

  1. Assemble all necessary documents, including insurance cards and ID.

  2. Make a mental note to discuss any asbestos exposure you may have experienced, including length, time and location of exposure.

  3. Plan to spend between 30 minutes and one hour at the doctor’s office.

This initial consultation often includes:

  • Medical History Review

  • Occupational History Review

  • Basic Physical Exam

  • Discussion of Symptoms

If you have a history of asbestos exposure, you will want to bring a summary of your work history and any documentation of your asbestos exposure. This information will help your doctor understand why you may be at risk of an asbestos-related cancer.

It’s impossible for someone to receive a mesothelioma diagnosis at their first consultation because of the biopsy testing required to detect cancerous mesothelioma cells. It won’t be the first disease that comes to mind for a primary care doctor or even for an oncologist. Some physicians may suggest pulmonary function tests, which measure how well your lungs are working. Chances are the general practitioner will send you to a specialist for more tests: Imaging scans or biopsies.

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Testing for Mesothelioma

Testing for mesothelioma is a long, complex process. It typically involves multiple cancer specialists and a series of diagnostic tools. The most widely used tests include imaging scans, biopsies and blood tests.

Imaging scans help doctors visualize abnormal growths on the body’s tissues and organs. Some show areas with high metabolic activity, suggesting cancer may be present. These scans help identify where biopsy samples should be collected, and if cancer is suspected, various blood tests may be ordered.

The most accurate test for confirming a diagnosis is a biopsy. It is a procedure where doctors remove tissue samples and study them under a microscope. Researchers also are exploring a variety of blood tests for substances that indicate mesothelioma. But, currently, none are accurate enough to confirm a diagnosis on their own.

However, researchers are making progress. In 2018, Swiss researchers published a study in the Archives of Pathology & Laboratory Medicine about a cytology test that may be able to accurately diagnose epithelial mesothelioma earlier than current approaches. The test is performed on samples of pleural effusion, which is less invasive to obtain than samples of tumor tissue for biopsies. The test cannot catch every case of mesothelioma early, but it could lead to quicker treatment for some patients.

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

Imaging Tests

Oncologists use imaging tests to check for visible signs of tumors. A mesothelioma diagnosis relies on a series of diagnostic imaging tests, including:

Produce basic images of dense areas, such as tumors, within the body
CT Scans
Use electromagnetic imagery to create detailed images of internal structures
Generate images of highly active internal structures using magnets and radio waves
PET Scans
Highlight areas of the body that have abnormally high, potentially cancerous metabolic activity

CT scans are most doctors’ first choice. The “gold standard” for mesothelioma imaging is a combination CT-PET. However, many mesothelioma tumors are seen incidentally. This happens when doctors use other types of scans to identify an unknown condition.

With results from these scans doctors can get a detailed look inside the body. It gives them a better idea of whether suspicious growths are cancerous or noncancerous.

Quick Fact:

In a study of 31 mesothelioma patients, PET and CT scans correctly identified 20 cases, incorrectly identified nine cases and could not determine two cases. MRI imaging correctly identified both undetermined cases in a follow-up scan.

If you are scheduled for a diagnostic imaging scan:

  • Assemble the same personal documents you collected for your first diagnostic appointment.

  • Plan for a one- to two-hour appointment.

  • Follow any pre-scan guidelines, such as fasting from food or water, provided by your doctor.

  • Research relaxation techniques if you are nervous about being in an enclosed scanning machine.

  • Plan to hear the results from your doctor within one to two weeks of the appointment.

A doctor may order a biopsy to confirm specific information if a scan reveals a mass on parts of the body (pleura, peritoneum or pericardium) where mesothelioma tumors typically develop.

Mesothelioma Biopsies

Biopsies are small fluid or tissue samples doctors send to a laboratory for evaluation when testing for mesothelioma. These tests can reveal whether a growth is cancerous, where in the body the cancer originated and what type of cells are involved. The cancer’s location and cell type play a major role when it comes to planning the treatment of mesothelioma.

Doctors can retrieve biopsy samples in several different ways:

Fine-Needle Aspiration
Extracts cells through a thin, hollow needle and a syringe.
Takes samples with a camera-equipped tube that doctors insert through the chest wall.
Mediastinoscopies are similar to thoracoscopies, except doctors insert the tube through an incision in the neck.
Removes pleural fluid buildup around the lungs to help diagnose the cause of pleural effusions.

Thoracoscopy is considered the most accurate diagnostic biopsy for mesothelioma. This method allows doctors to look into the pleural cavity and retrieve high-quality biopsy samples. It can result in accurate diagnosis for up to 98 percent of mesothelioma patients.

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Blood Tests

Researchers have spent a considerable amount of time developing mesothelioma blood tests. These tests analyze your blood for proteins and other substances (biomarkers). Early studies suggest these blood tests have the potential to play a role in testing for mesothelioma. They are not yet reliable enough to confirm a diagnosis on their own.


The FDA-approved MESOMARK test can detect soluble mesothelin-related peptide (SMRP). SMRP is a protein and mesothelioma biomarker. Extensive research shows that SMRP is helpful to monitoring tumor response to treatment, but it cannot definitively diagnose mesothelioma. Too many false positives are recorded and some cases of cancer go undetected using MESOMARK. The test’s potential to screen for mesothelioma among people exposed to asbestos is questionable as well. One study found it helpful at identifying persons at risk of mesothelioma and another study did not.


The SOMAmer test can detect more than 1,000 proteins in blood serum. These proteins may have diagnostic value in identifying mesothelioma. A 2012 study analyzed blood serum samples from 117 malignant mesothelioma cases and 142 people exposed to asbestos. These samples detected 13 protein biomarkers that helped to accurately identify malignant mesothelioma.

The test accurately detected malignant mesothelioma in 90 percent of cases and ruled out the cancer in 95 percent of people without the cancer. The biomarker levels correlated with cancer stage. This indicates the test may have value in monitoring the progress of mesothelioma. Continued analysis of more cases of mesothelioma is needed to validate the worth of the SOMAmer test.

Human MPF

The Human MPF test measures a protein called megakaryocyte potentiation factor (MPF). MPF is produced by a mesothelin precursor protein. MPF levels increase as mesothelioma tumors grow and are detected in about 91 percent of late-stage patients. The test can rule out mesothelioma in 95 percent of people who don’t have the cancer. But, it accurately identifies the cancer in only 64 percent of people with mesothelioma. The test isn’t sensitive enough to help with diagnosis. It could help doctors monitor the cancer’s progression and response to treatment.

Diagnostic Capabilities of Mesothelioma Blood Tests
Test Sensitivity 1 Specificity 2
MESOMARK 68% 92%
SOMAmer 90% 95%
Human MPF 68% 95%
  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.

Researchers continue to refine these tests for diagnosing mesothelioma. They can still play a role in tracking how mesothelioma is progressing in patients.

Staging Mesothelioma

The diagnostic tools used prior to surgery help doctors estimate the cancer’s stage of progression, which is called clinical staging. These tools are advanced, but directly examining the body through surgery is the most accurate way to determine a cancer’s stage.

Imaging tests are the most noninvasive tools doctors have for estimating the growth and spread, or stage, of mesothelioma cancer. The images created by the scans give an inside view of the body that shows where tumors are growing. Radiologists use these images to identify how far the cancer has spread and then assign a stage based on what they see.

For example, if the images show little tumor growth in a small area on one lung, the cancer could be in stage 1 or 2. If the image shows extensive tumor spread throughout the lungs, diaphragm and possibly into the abdomen, the cancer is likely in stage 4.

Some minimally invasive diagnostic techniques are used to estimate stage such as thoracoscopy or mediastinoscopy. They can help determine if the cancer has spread beyond the pleural lining or into lymph nodes.

However, surgery is the most accurate way to diagnose mesothelioma. Unfortunately, surgery is an invasive procedure and can’t be performed on patients who are in poor health or have late-stage mesothelioma. Imaging scans work well enough to identify late-stage tumor spread. This precludes patients from surgery because the cancer has grown to the point that surgical removal becomes life-threatening.

A 2012 study that analyzed more than 3,000 pleural mesothelioma cases reported on the discrepancy of staging based on clinical versus surgical staging. It showed clinical staging is most accurate for stage 3 and 4 cases. Around 80 percent of patients with clinical stage 1 cancer were found to have more advanced disease upon surgery, known as upstaging. About 65 percent of patients with clinical stage 2 mesothelioma were upstaged, but only 20 percent with stage 3 and none with stage 4 were upstaged.

Thoracic surgeon Dr. Jacques Fontaine talks about the difficulty of diagnosing mesothelioma and why it's so important to get treated at a specialty cancer center.


Sometimes mesothelioma is misdiagnosed as a less serious disease or another cancer. The initial symptoms of mesothelioma can resemble other conditions such as pneumonia or irritable bowel syndrome. It is common for the cancer to be misdiagnosed as a nonterminal condition.

An initial misdiagnosis is common for people who have mesothelioma. As the cancer progresses and more serious symptoms develop, increasingly advanced testing becomes warranted. Advanced testing leads to an accurate diagnosis.

However, mesothelioma can also be misdiagnosed as other forms of cancer. It is most commonly misdiagnosed as a form of lung cancer that develops in mucus-secreting glands called adenocarcinoma. Pathologists are the professionals who analyze tumor biopsy samples. If they aren’t experienced with differentiating mesothelioma from other cancers, a misdiagnosis can occur.

Working with a cancer center that specializes in mesothelioma can confirm or deny the diagnosis. The professionals working at such cancer centers have the experience that’s necessary to accurately diagnose the disease.

After a Mesothelioma Diagnosis

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

After a mesothelioma diagnosis, be sure to learn about your type of mesothelioma and the therapies that may help you live longer. The more you know, the better prepared you’ll feel.

Discuss your treatment plan in great detail with your health care team. Thorough communication will help you feel more comfortable and secure with the plan. Ask about complementary therapies that may help with side effects. For example, acupressure may help with chemotherapy-induced nausea.

Divulge any medications or supplements you are taking. They could interfere with treatment.

Always ask your health care team or a patient advocate about financial assistance options such as travel grants. And don’t forget to reach out to family, friends and health professionals for support.

Building a mesothelioma support network will help you and your loved ones cope with this cancer.

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Registered Nurse and Patient Advocate

Karen Selby joined in 2009. She is a registered nurse with a background in oncology and thoracic surgery and was the regional director of a tissue bank before becoming a Patient Advocate at The Mesothelioma Center. Karen has assisted surgeons with thoracic surgeries such as lung resections, lung transplants, pneumonectomies, pleurectomies and wedge resections. She is also a member of the Academy of Oncology Nurse & Patient Navigators.

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Last Modified April 8, 2019

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