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How Do Doctors Diagnose Malignant Mesothelioma?

Mesothelioma is a type of cancer that’s often difficult to diagnose. It is caused by exposure to asbestos, a carcinogenic mineral widely used throughout the 20th century. Mesothelioma has an extremely long latency period, meaning it can take decades after the initial asbestos exposure for the disease to develop.

Because mesothelioma is so rare and takes years to develop, it can take a long time to accurately diagnose the disease. It can be a stressful and time-consuming process. If you show symptoms of mesothelioma, such as chest or abdominal pain or a persistent cough, contact your primary care doctor immediately, especially if you know or suspect that you encountered asbestos in the past. Due to its aggressive nature, early detection can greatly improve a mesothelioma prognosis.

The Mesothelioma Diagnosis Process

Generally, patients undergo a number of blood tests, imaging tests, and biopsies, in addition to a thorough physical examination.

Imaging tests

The mesothelioma diagnosis process generally begins with a series of imaging tests, starting with the lowest resolution scans and working up if needed.

This diagram shows each kind of imaging machine used for diagnosing mesothelioma and the amount of time those tests take.

X-rays are low-resolution, low-radiation images that give doctors a two-dimensional glimpse into the body. Irregularities that may indicate the presence of mesothelioma, such as fluid buildup, pleural thickening, tumors, and irregularities in lung size, are usually visible with an X-ray. Abnormal scans may prompt doctors to move on to higher-resolution imaging tests. The average X-ray only takes around 15 minutes.
CT scan
Computed tomography scans (also referred to as CT or CAT scans) combine rotating X-rays with computers to create multi-angled images of the body. They show if abnormalities are present and give doctors a deeper understanding of the extent and exact location of the abnormality, making them particularly helpful in diagnosing cancer. A CT scan lasts between 10 and 30 minutes, depending on the part of the body.
PET scan
Positron emission tomography scans, or PET scans, use a small dosage of radiotracer, a radioactive chemical, to produce three-dimensional images. PET scans can show changes in an organ or tissue at a cellular level, where most diseases begin. This technology allows doctors to determine the stage of mesothelioma based on how far it has spread throughout the patient’s body. Once patients are injected with the radiotracer, it takes about an hour to travel through the body and be absorbed by the affected organs or tissues. The actual scan takes an additional 30 to 60 minutes.
MRIs (magnetic resonance images) use powerful magnetic fields and a computer rather than radiation to create high-resolution, three-dimensional images of affected areas in a patient’s body. They are used to identify areas that may require a biopsy and are often used for staging mesothelioma. MRI test times range from 15 minutes to nearly an hour. Patients with claustrophobia (or a fear of enclosed spaces) may receive anti-anxiety medication, which requires longer recovery time.

Blood tests

Following imaging tests, blood tests tend to be next in line when diagnosing mesothelioma. The most common blood tests doctors use to diagnose mesothelioma are listed below.
This image shows a doctor following up on an image test by taking some blood from the patient.

Cancer antigen (CA 125)
Cancer antigen 125 is a protein biomarker found in large concentrations of cancer cells. The CA 125 test measures how much of the protein is present in a patient’s blood. When factored in with stage and tumor location, a change in CA 125 levels can help determine a patient’s mesothelioma diagnosis as well as anticipate their response to systemic chemotherapy.
Mesothelioma patients tend to demonstrate high levels of fibulin-3, another biomarker. The fibulin-3 blood test helps doctors distinguish between a mesothelioma diagnosis and other lung diseases. Tracking a patient’s fibulin-3 levels can also be helpful in measuring the efficiency of their treatment.
Gaining FDA approval in 2007, MesoMark® was the first blood test to be used for mesothelioma diagnoses. MesoMark® works by measuring levels of soluble mesothelin-related proteins released by diseased cells, allowing doctors to assess the severity of mesothelioma present in the body. However, because sarcomatoid mesothelioma does not release these proteins, MesoMark® is unable to assist in the diagnosis of this mesothelioma cell type and should be used in concurrence with other tests to ensure an accurate diagnosis.


A biopsy involves the removal of fluid or tissue in order to determine the presence or scope of the disease. In mesothelioma patients, biopsies allow doctors to determine whether the cancer has spread and, if so, to what extent. Cytology reports are used to test samples retrieved from fluid biopsies for mesothelioma cells. Fluid biopsies are less invasive than tissue biopsies. However, because mesothelioma can mirror other conditions, a tissue biopsy is required to achieve a conclusive mesothelioma diagnosis and is usually necessary in order to pursue legal claims.

A biopsy is the only conclusive way to diagnose mesothelioma.

The most common biopsies include needle biopsies, camera-assisted biopsies, and surgical biopsies.

Needle biopsies

Sometimes called a closed biopsy, needle biopsies are the least invasive type of biopsy available for a mesothelioma diagnosis. They are generally outpatient procedures, meaning patients can come the same day.

Mesothelioma Hub - Needle This image shows the third step of diagnosing mesothelioma, where a doctor will take a sample of fluid from the area and run a test on it.

Pleural biopsy
The most common needle biopsy, doctors perform pleural biopsies on patients experiencing fluid buildup between their lungs and chest (pleural effusion). An anesthetic is first injected to numb the area. Then, the doctor inserts a needle to collect a sample of the pleural fluid and tissue to check for the presence and extent of mesothelioma. The procedure usually lasts about 30 minutes to an hour.
Similar to a pleural biopsy, during paracentesis, a doctor inserts a needle into the patient’s peritoneal cavity to retrieve a sample of the ascitic fluid buildup in the abdomen. This procedure allows doctors to test for the presence of mesothelioma, as well as relieve patient discomfort. Depending on the level of fluid buildup, this procedure usually takes about 30 minutes.
Also similar to a pleural biopsy, thoracentesis involves the draining of fluid in the pleural cavity. It is done for diagnostic purposes as well as to reduce patient pain and discomfort. The procedure is fast, usually around 15 minutes in total.
For patients experiencing fluid buildup around the heart sac (pericardial effusion), a pericardiocentesis procedure may be done to drain the fluid and prevent future buildup. Like other needle biopsies, pericardiocentesis can be helpful in the diagnostic process as well as alleviating patient pain. The procedure usually takes between 20 minutes to an hour.
Camera-assisted biopsies

Camera-assisted biopsies involve a small camera, a computer, and surgical instruments. Generally, a doctor will perform a camera-assisted biopsy after a needle biopsy and before a surgical biopsy.

The next step to diagnosing mesothelioma, as seen in this illustration, is to use a special camera to examine the area the doctors believe to be afflicted.

During this minimally invasive procedure, a surgeon makes a small incision to insert a viewing tube into the chest cavity. The doctor is able to capture a diagnostic sample and relieve the patient of some discomfort by draining excess fluid. The procedure ranges from 45 to 90 minutes.
Laparoscopy (sometimes called peritoneoscopy)
Similar to thoracoscopy, laparoscopy involves making a small incision that allows doctors to insert a viewing tube into the abdomen. Doctors are able to examine the affected abdominal organs and take diagnostic samples. This procedure usually lasts around 75 minutes.
This camera-assisted biopsy procedure allows doctors to examine the lymph nodes and see if the mesothelioma has spread. It generally takes about 60 to 90 minutes.
Surgical biopsies

A surgeon will perform a surgical biopsy when less invasive biopsies fail to provide definitive results. They are conducted under general anesthesia.

The final and most accurate way to diagnose mesothelioma is with a surgical biopsy where they remove and examine a part of the suspect tumor.

When a tumor is detected in the chest, a thoracotomy may be performed. During this surgical procedure, the surgeon makes an incision in the chest to take a tissue biopsy. When possible, the surgeon will also remove as much of the tumor as possible during this procedure.
When a tumor is detected in the abdomen, a laparotomy may be performed. During this surgical procedure, the surgeon makes an incision in the abdomen to take a tissue biopsy. When possible, the surgeon will also remove as much of the tumor as possible during this procedure.

Keep a copy of all test results and scans for your records. You should also keep a record of your symptoms, medications, and any questions you have for your doctor.

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Mesothelioma Hotline

We’re here for you every step of the way.

(205) 271-4100