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Mesothelioma Diagnosis

Diagnosing mesothelioma in a patient who is showing symptoms is a multi-step process. It involves discussing the patient’s medical history and past asbestos exposure, along with testing via chest X-rays, CT scans, and biopsies. Since mesothelioma is rare, it is often recommended to obtain a second opinion to ensure a correct diagnosis.

Patricia Shelton

Medically Reviewed By:
Patricia Shelton, M.D.

Patricia Shelton

Medically Reviewed By:Patricia Shelton, M.D.

How Is Mesothelioma Diagnosed?

Mesothelioma diagnosis begins with a review of your medical history, which may include a discussion of your risk factors, especially your history of asbestos exposure. The doctor will perform a physical exam and begin imaging studies, which are discussed below.


Chest X-Rays

Your Doctor may order a chest X-ray if you have respiratory symptoms. If you have pleural mesothelioma, the X-ray may show areas where the pleura are thickened or have areas of calcification, which indicate inflammation. These changes may be suggestive of cancer but cannot establish what type of cancer it is.


Computed Tomography Scan (CT scan)

This scan produces detailed 3D images that allow doctors to more precisely visualize a tumor and look for any additional tumors. Contrast dye, which is injected into a vein in order to make certain structures more visible, is sometimes used. A CT scan of the abdomen is a common first step in the diagnosis of peritoneal mesothelioma. For patients with pleural mesothelioma, CT scans of the chest are often used to follow up on a concerning finding on a chest X-ray.

Vaccines like Gardasil

Blood Tests

While there are no definitive biomarkers for mesothelioma, certain blood tests can indicate the possibility of mesothelioma. The following blood factors are commonly higher in people with mesothelioma:

  • Elevated levels of the glycoprotein Fibulin-3
  • Elevated levels of Osteopontin, another glycoprotein
  • An elevation of soluble mesothelin-related peptides on cell surfaces

Soluble mesothelin-related peptides are the most studied biomarker. They may be elevated for years before mesothelioma is diagnosed. This test is marketed under the brand MESOMARK. Unfortunately, it suffers from low sensitivity in testing, making the test unreliable if the results are negative.

While these tests can be useful, none is scientifically proven to reliably test for mesothelioma.



Doctors must have the results of a biopsy to definitively diagnose mesothelioma. A pathologist examines this small sample of the tumor tissue under a microscope and subjects it to a variety of tests to look for specific abnormalities in the cells. This is known as cytology, and it can reveal whether the patient has cancer and, if so, what type.

Many types of biopsies are used for diagnosing mesothelioma.

Core Needle Biopsy

If the tumor is close to the skin, then it may be possible to obtain a core needle biopsy. The biopsy sample is taken using a needle passed through the skin into the tumor. Ultrasound may be used to help guide the precise needle placement.

Fluid Biopsy

Some patients have a buildup of fluid around the lungs or in the abdomen. In some cases, a sample of this fluid is analyzed to check for cancer cells.


In a thoracentesis, a doctor uses a needle or a catheter (a thin plastic tube) to drain fluid from a pleural effusion, which is a buildup of fluid around the lungs.


In a paracentesis, the fluid from ascites, or fluid buildup in the abdomen, is drained using a needle or a catheter.

Endoscopic Biopsy

An endoscopic biopsy is a surgical procedure in which small incisions are made and an instrument called a scope is inserted. Using a camera on the end of the scope, the surgeon can visualize the inside of the body. They can also obtain tissue samples through the scope using specially designed surgical instruments.


For pleural mesothelioma diagnosis, the most common procedure is a thoracoscopy. Through small incisions in the chest wall, the surgeon can visualize the inside of the thoracic cavity to look for tumors and obtain one or more biopsy samples.


Peritoneal mesothelioma diagnosis may involve a laparoscopy, in which the surgeon uses a laparoscope to look around the abdominal cavity and get biopsy samples.

Open Surgical Biopsy

In some cases, when an endoscopic biopsy isn’t enough, an open surgical biopsy may be needed. This involves making a larger incision to allow the surgeon to see the inside of a body cavity directly rather than through a scope. For pleural mesothelioma patients, the procedure used is called a thoracotomy, while for peritoneal mesothelioma, it’s a laparotomy.

Tests for Staging

Mesothelioma staging is an important part of a mesothelioma diagnosis. Staging is the process of determining how advanced the cancer is. It is crucial in creating a treatment plan because cancer treatment options are different in an early stage from in an advanced stage.

The stage of mesothelioma is determined by the tumor size at diagnosis, whether it has spread to the lymph nodes, and whether it has spread to distant locations in the body.

Doctors may use additional imaging studies for staging mesothelioma.

Magnetic Resonance Imaging (MRI)

An MRI may be helpful in localizing tumors and checking for additional tumors around the body. MRI scans sometimes involve the use of contrast dye.

Positron Emission Tomography Scan (PET scan)

PET scans use a tracer to look for malignant cells. This is helpful in determining whether the cancer has spread to lymph nodes or has undergone metastasis, or spread to other parts of the body.

CT Scans

CT scans make a detailed cross-section of your body to show if the cancer has spread to other organs. A CT scan can identify the exact locations of mesothelioma in your body.


A needle biopsy may be used to determine whether cancer has spread to the lymph nodes.

A mediastinoscopy may be used to confirm cancer has spread to the lymph nodes if other testing suggests this may have occurred. During a mediastinoscopy, a scope is inserted into the tissue in the center of the chest, known as the mediastinum.

Pathology Testing

Mesothelioma occurs in a variety of cell types and sub-types. Each of these has characteristics that affect your treatment options and prognosis. After your initial diagnosis, your doctor will order histology testing to narrow down your diagnosis to one of the following mesothelioma cell types:

Cytology studies will also be performed to identify even more specific data, including the individual cells’ shape, size, and other characteristics.

How Long Does It Take to Get a Mesothelioma Diagnosis?

Although receiving a biopsy result within one to two days is possible, the entire diagnostic process may take several months. Due to the difficulty in diagnosing mesothelioma, you may be incorrectly diagnosed with other more common conditions initially, and you will most likely go through a series of tests each time your symptoms worsen until mesothelioma is finally suspected.

Once a doctor suspects mesothelioma, you may be able to receive a diagnosis within days or weeks. The process of eliminating more common conditions is the primary factor that delays a mesothelioma diagnosis.

Is it Possible to Detect Mesothelioma Early?

It is possible but not common. When mesothelioma starts causing symptoms, it has usually already reached an advanced stage.

There are no established guidelines for mesothelioma screening in asymptomatic individuals. If you are aware that you have been exposed to asbestos, your doctor may recommend that you undergo annual imaging and lung function tests in hopes of detecting mesothelioma early, should it occur.

Early detection of mesothelioma may improve your prognosis. However, medical studies have yet to confirm that any form of mesothelioma pre-screening is beneficial overall. Research into early biomarkers for mesothelioma is ongoing.

Why Is Mesothelioma So Hard to Diagnose?

The diagnosis of mesothelioma is fairly challenging. This is related due to a few different features of this particular cancer.

Symptoms of Mesothelioma

The symptoms of mesothelioma are nonspecific. “Nonspecific” is a term used in medicine to denote symptoms that can be caused by a wide variety of diseases. The symptoms caused by mesothelioma are nearly identical to those of many other respiratory conditions.

Because so many other conditions are far more common than mesothelioma, you may be misdiagnosed—even multiple times—before you receive a correct diagnosis. Pleural mesothelioma, which impacts the membranes surrounding the lungs, may be misdiagnosed as the following:

  • Lung cancer
  • Drug-induced complications
  • Benign pleural mass
  • Lung infection
  • Scarring of the lungs, or asbestosis

Peritoneal mesothelioma, which is cancer of the lining around the stomach, also presents with vague symptoms, which could result in the following misdiagnoses:

  • Peritoneal carcinomatosis
  • Serous peritoneal cancer
  • Ovarian cancer
  • Lymphomatosis
  • Tuberculous peritonitis

The Long Latency Period

Mesothelioma typically develops 20 to 40 years or even longer after asbestos exposure. This extended latency period makes it easy to forget about asbestos exposure, so you may not think to inform your doctor that you have been exposed to asbestos. As a result, doctors don’t think to test for mesothelioma.

The Rarity of Mesothelioma

The disease is relatively rare. Mesothelioma makes up 0.17% of all cancer diagnoses in the United States, and there are roughly 3,000 cases diagnosed each year. Doctors learn about mesothelioma in medical school, but they are unlikely to encounter the disease during their careers. Many doctors fail to consider mesothelioma a possible diagnosis, particularly early in the diagnostic process.

Difficulty Identifying Mesothelioma

There is no blood test or imaging test that can definitively diagnose mesothelioma. The only conclusive way to diagnose it is with a biopsy. Even with an adequate tissue sample, pathologists must perform detailed studies and may require a second opinion from a specialist. In addition, mesothelioma often resembles other types of cancer under a microscope.

These factors can contribute to misdiagnosis of mesothelioma and make early cancer detection difficult.

What to Do After a Mesothelioma Diagnosis

Seek Medical Treatment

After a malignant mesothelioma diagnosis, the most important priority is commencing treatment because this cancer grows and spreads aggressively. Since most doctors have little or no experience treating mesothelioma, you will need treatment at a specialized mesothelioma treatment center.

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