Mesothelioma diagnosis

You may need to have several tests before your doctors can make an accurate diagnosis. Learn more about how mesothelioma is diagnosed.

How mesothelioma is diagnosed

You usually begin by seeing your GP. They will ask you about your symptoms and examine you. They may also ask if you have been exposed to asbestos in the past. You may have blood tests and a chest x-ray.

Depending on the results of any tests, your GP may refer you to hospital for further tests. At the hospital, you will see a specialist doctor. They will ask you about your general health and any previous medical problems.

The specialist may ask if you have been exposed to asbestos in the past. This might include jobs you have had or places you have worked. They may also ask if anyone in your family worked with asbestos.

It usually takes a long time for mesothelioma to develop after exposure to asbestos. You may have to think back to your childhood or early working years.

You may get anxious before the appointments. This is natural. It may help to get support from family, friends or a support organisation.

Tests for pleural mesothelioma

Pleural mesothelioma often starts as tiny lumps (nodules) in the pleura. These will not show up on x-rays or scans until they are quite large.

If fluid has developed between the two layers of the pleura (pleural effusion), this usually shows up on a chest x-ray at an earlier stage. A pleural effusion can also develop because of other cancers and some non-cancerous conditions.

You may need to have a few different tests before your doctors can make a diagnosis. Your doctor or nurse will tell you about the most suitable tests for you and what they involve.

Chest x-ray

A chest x-ray checks your lungs for anything that looks abnormal, such as thickening of the pleura or fluid around the lungs. These symptoms can be caused by conditions other than mesothelioma.

CT scan

A CT scan makes a three-dimensional (3D) picture of the inside of the body using x-rays taken by the CT scanner

Draining fluid from the pleura (pleural aspiration)

Mesothelioma cells can cause fluid to build up between the two layers of the pleura around the lung. This is called a pleural effusion. Draining the fluid may help with your breathing. Your specialist doctor may take a sample of this fluid to be checked for mesothelioma cells.

Pleural biopsy

During a biopsy, a small piece of tissue is removed so that it can be looked at under a microscope. Your doctor may suggest a biopsy of the thickened pleura.

A pleural biopsy is more likely to confirm the diagnosis of mesothelioma than a sample of fluid. Your doctor may take a pleural biopsy in different ways.

  • CT or ultrasound guided biopsy

    The doctor will give you a local anaesthetic to numb the area. They use an ultrasound or CT scan to help guide them to the right place. Then, they pass a special type of needle through your skin into the thickened area. The needle has a tip that can cut out a small sample of tissue.

  • Thoracoscopy

    The doctor uses a thin tube (thoracoscope) to look at the pleura and the area around the lungs. They may also take biopsies.

Talc pleurodesis

After draining fluid or taking a biopsy, the doctor may put a sterile, medical grade talcum powder (talc) between the layers of the pleura. This helps prevent the fluid coming back. This is called talc pleurodesis.

Tests on the lymph nodes around the lungs

You may have tests on the lymph nodes around the lungs. This is not common, but may happen if:

  • your doctor thinks you might be able to have surgery to treat the mesothelioma
  • you were having tests for lung cancer before mesothelioma was diagnosed.

Tests for peritoneal mesothelioma

You may have several different tests to help diagnose peritoneal mesothelioma.

Abdominal x-ray

An abdominal x-ray checks for anything abnormal in your tummy area (abdomen).

CT scan

A CT scan makes a three-dimensional (3D) picture of the inside of the body using x-rays taken by the CT scanner.

MRI (magnetic resonance imaging) scan

An MRI scan uses magnetism to build up a detailed picture of areas of your body.

Draining fluid from the abdomen (peritoneal aspiration)

Mesothelioma cells can cause fluid to collect in the abdomen. This is called ascites. Your doctor may take an aspirate (a sample of this fluid) to send to the laboratory, to see if it contains mesothelioma cells.

Peritoneal biopsy

During a biopsy, a small piece of tissue is removed so that it can be looked at under a microscope. Your doctor may suggest a peritoneal biopsy (lining that covers the organs in the tummy) to help diagnose peritoneal mesothelioma. It can be done in 2 ways.

  • Laparoscopy

    A laparoscopy allows the doctor to look at other areas in your tummy (abdomen) and take more biopsies if needed. It is done under general anaesthetic. Your doctor will make a small cut in the tummy wall. They will put a thin tube with a light and camera at the end (laparoscope) into your tummy. They can then take a small biopsy of the peritoneum. They will also check nearby organs to see if the mesothelioma has spread.

  • CT or ultrasound guided biopsy

    The doctor will give you a local anaesthetic to numb the area. They use an ultrasound or a CT scan to help guide them to the right place. Then, they pass a special type of needle through your skin into the area they want to take a biopsy from. The needle has a tip that can cut out a small sample of tissue.

After a biopsy

Having a biopsy can be uncomfortable but should not be painful. If you have any pain during or after the procedure, tell your doctor or nurse.

After the doctor has taken the biopsy, they will send it to the laboratory. A doctor who looks at cells or body tissue under a microscope to diagnose cancer (pathologist) will look at the biopsy.

Sometimes, even after taking a biopsy the doctors may not be sure of the diagnosis. This is because it can be difficult to find the difference between mesothelioma and some other cancers and illnesses. If this happens, the samples may be sent to specialist laboratories to confirm the diagnosis. Sometimes you may need to have a test done again, or you may be referred to another hospital for a second opinion.

About our information

  • References

    Below is a sample of the sources used in our mesothelioma information. If you would like more information about the sources we use, please contact us at cancerinformationteam@macmillan.org.uk

    Woolhouse I et al. British Thoracic Society Guideline for the investigation and management of malignant pleural mesothelioma. Thorax. 2018.

    Thomas A et al. Mesothelioma. BMJ Best Practice. 2019.

    Baas P et al. Malignant pleural mesothelioma: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up.  Annals of Oncology. 26 (Supplement 5): v31–v39. 2015. Available from: www.pubmed.ncbi.nlm.nih.gov/26223247

    Kusamara S et al. Peritoneal mesothelioma: PSOGI/EURACAN clinical practice guidelines for diagnosis, treatment and follow-up. European Journal of Surgical Oncology. March 2020.


  • Reviewers

    This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer. It has been approved by Senior Medical Editor, Dr David Gilligan, Consultant Clinical Oncologist.

    Our cancer information has been awarded the PIF TICK. Created by the Patient Information Forum, this quality mark shows we meet PIF’s 10 criteria for trustworthy health information.