Mesothelioma Diagnostic Steps and Criteria

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Mesothelioma can be mistaken for other cancers, so it is vital to have cancer diagnosed correctly as early as possible.

Basic Diagnostic Steps for Mesothelioma

The basic mesothelioma diagnosis criteria are as follows: (

  • Symptoms: Mesothelioma symptoms will cause the patient to visit their doctor for an examination and tests. Common symptoms are a persistent cough, pain in the back or side, coughing up blood, difficulty breathing, and unexplained weight loss.
  • Mesothelioma testing: The first tests for suspected mesothelioma are a chest X-ray or CT scan. These tests can reveal abnormal growths, which can lead to additional testing and possibly a referral to an oncologist.
  • Confirm cancer diagnosis: The oncologist will use several imaging scans, blood tests, and biopsies to confirm the diagnosis. A blood test or imaging scan alone cannot confirm a mesothelioma diagnosis. (org)

One of the challenges of diagnosing mesothelioma is the path to diagnosis can vary among patients. Mesothelioma can mimic less serious medical conditions, so doctors may initially confuse this deadly asbestos cancer for pneumonia or another type of cancer.

It is common for pleural mesothelioma patients to be diagnosed with lung cancer or pneumonia. Peritoneal mesothelioma patients may be misdiagnosed with more common forms of abdominal cancer.

Giving your doctor your complete work history with any level of asbestos exposure is important. Your physician may not look for mesothelioma unless she knows you were exposed to the deadly substance. Also, mesothelioma can occur up to 50 years after initial exposure, so mesothelioma is often not the first disease doctors are looking for.

Testing for Mesothelioma

Standard diagnostic criteria and tests for mesothelioma include imaging scans, blood tests, and biopsies. Imaging tests such as X-rays and CT scans can identify possible mesothelioma tumors. But a tumor biopsy is the only definite way to confirm that a patient has mesothelioma. Blood tests for the cancer are used to measure how the patient is responding to treatment.

More information about imaging tests to diagnose mesothelioma:

  • X-rays: Makes basic images of body areas with various densities, such as fluid or tumors.
  • CT scans: Also called CAT scans. These images use computer software to collect hundreds of fine X-rays images to make detailed images of internal body structures. These images show much more detail than a regular X-ray.
  • MRIs: Using electromagnetic technology, MRIs produce precise images that are highly useful when looking at nerve, bone, or brain tissue.
  • PET scans: This is a form of CT scan where the patient receives a dose of radioactive glucose in the blood, which makes inflamed cells show on scans. Cell inflammation could be caused by an infection or rapid cell growth, which can be cancer.

Mesothelioma Biopsies

Biopsies are essential to confirm a diagnosis for mesothelioma. Below are the types of biopsies used to confirm various cancers: (

  • Thoracoscopy: While under general anesthesia, the surgeon will place a small camera between your ribs to suck out some of the pleural fluid. He also will review the appearance of the inside of your chest and take biopsies. This is the most accurate biopsy for mesothelioma.
  • Mediastinoscopy: Under general anesthesia, the surgeon will place a small camera at the base of your neck to get a biopsy of your lymph nodes near the windpipe.
  • Thoracentesis: Using local anesthesia and with an ultrasound probe, a small needle is placed between your ribs in your back to take out pleural fluid buildup surrounding the lungs. This biopsy is used to diagnose what is causing a pleural effusion.
  • Fine-needle aspiration: Under local anesthesia, a small needle is placed between your ribs to sample or biopsy tumors while you are in the CT scan machine.
  • Endobronchial ultrasound-guided biopsy: A 2016 study found this form of biopsy can help to diagnose pleural mesothelioma when other biopsy techniques are ineffective.

Mesothelioma Blood Tests and Biomarkers

Mesothelioma blood tests, biomarkers, and immunohistochemical markers are useful but insufficient to diagnose the cancer alone. They are helpful to monitor how the patient is responding to cancer treatments: (

  • MESOMARK: This is an FDA-approved blood test that can detect tiny quantities of soluble mesothelin-related peptide, which can be an indicator of mesothelioma tumors in the body.
  • SOMAmer: Can detect at least 1,000 proteins in the blood. These proteins can be useful in finding mesothelioma cells in the body.
  • Human MPF: Measures a protein called megakaryocyte potentiation factor.

Difficulties in Diagnosing Mesothelioma

Staging mesothelioma is a key part of the diagnostic process, but it is challenging. Staging tells the doctor how far the cancer has progressed; this is the biggest factor in determining the treatments that are best for the patient.

The cancer stage is also a major factor in how long the patient will live after diagnosis:

  • Clinical staging: Uses several imaging scans and biopsies to determine the stage. Imaging tests, such as PET scans, are the best tools doctors have to estimate cancer stage. If the PET or CT scan shows tumors have spread to other organs, a needle biopsy may be needed to confirm the spread.
  • Surgical staging: Biopsy procedures such as mediastinoscopy and thoracoscopy can be used to determine how far the cancer has advanced beyond the pleural lining or lymph nodes.


Mesothelioma is diagnosed in only about 3,000 people per year, so many doctors are not trained to look for it initially:

  • Pleural mesothelioma can be misdiagnosed as heart failure or pneumonia.
  • Peritoneal mesothelioma can be misdiagnosed as irritable bowel syndrome.
  • Pericardial mesothelioma can be misdiagnosed as coronary heart disease.

All of these cancers can be misdiagnosed as other forms of cancer. For example, pleural mesothelioma can be misdiagnosed as a type of lung cancer called adenocarcinoma.

Peritoneal mesothelioma can be misdiagnosed as ovarian or colon cancer.

What to Do After Your Cancer Diagnosis

If you have an asbestos exposure history and have been diagnosed with another type of cancer, it is wise to seek a second opinion from a mesothelioma specialist. Choosing a physician and cancer center that focuses on mesothelioma can confirm your diagnosis and get you the access you need to the best treatments.


Many tests need to be performed to confirm a mesothelioma diagnosis. Be sure to talk to your doctor about any asbestos exposure history you have so that he is watching for possible mesothelioma tumors. If you are diagnosed with another cancer, consider seeking a second opinion to ensure you are getting the treatment you need.