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Diagnosing mesothelioma


Mesothelioma can be challenging to diagnose. The symptoms are often the same as those of other diseases, and mesothelioma cells can look similar to other types of cancer cells and even look like normal cells.

Diagnosing mesothelioma usually starts with a visit to your GP or going to a hospital emergency room, perhaps for shortness of breath or pain. If you think you may have been exposed to asbestos in the past, it is important to let your doctor know as many doctors won’t automatically suspect mesothelioma.

Sometimes, even after several tests, the doctors may be unsure of the diagnosis and some tests may need to be repeated. 

Your guide to best cancer care

A lot can happen in a hurry when you’re diagnosed with cancer. The guide to best cancer care for mesothelioma can help you make sense of what should happen. It will help you with what questions to ask your health professionals to make sure you receive the best care at every step.

Read the pleural mesothelioma guide

Read the peritoneal mesothelioma guide 

General tests

Blood tests and x-rays can provide information about your overall health and help to rule out other conditions.

  • Blood test – to check your general health and let your doctors know how your blood cells, liver and kidneys are working. This helps them work out whether you’re fit enough for treatment. Mesothelioma does not usually show up with a blood test, but results may show substances called markers that are produced by cancer cells. 
  • X-ray – If pleural mesothelioma is suspected, you will have a chest x-ray to look for any changes in the lungs, thickening of the pleura, and fluid in the space between the lungs and the chest wall. For peritoneal mesothelioma, an x-ray will look for changes in the abdomen, such as fluid and thickening in the peritoneum. 

CT scan

A CT (computerised tomography) scan uses x-rays and a computer to create a detailed picture of an area inside the body. The procedure is painless and takes about 30 minutes. Before the scan, you will be given an iodine contrast dye to make the scan pictures clearer.

The CT scan shows the location and thickness of the tumour(s) in the chest or abdomen. It can also show if the mesothelioma has spread to other organs. The information from the CT scan is used to work out the best way to get tissue for testing.


A biopsy is the main test used to diagnose mesothelioma. It involves removing a sample of tissue, which is examined under a microscope by a specialist doctor called a pathologist.

The pathologist looks for cell changes to work out if the tumour is mesothelioma and, if so, the type of mesothelioma cells present. Mesothelioma is usually classified according to how the cells look under a microscope (although in about 27% of cases, the classification is unknown).

There are three main types of mesothelioma cells:

  • Epithelioid (about 70% of cases) – cells look similar to normal mesothelial cells.
  • Sarcomatoid (about 10–15% of cases) – cells have changed and look like cells from fibrous tissue.
  • Mixed or biphasic (about 10–15% of cases) – has epithelioid and sarcomatoid cells. 

Ways to take a biopsy

A biopsy can be taken in different ways. The choice of biopsy will depend on your general health and fitness, and how suitable the tumour is for sampling. Keyhole surgery (VATS or laparoscopy) is the most common biopsy technique as both tissue samples and fluid can be removed for testing.

Video-assisted thoracoscopic surgery (VATS)

This is used to obtain a tissue sample from the lining of the lungs (pleura). You will be given a general anaesthetic, then a thin tube with a light and camera will be inserted through a few small cuts in your chest. Tissue samples can be taken through the tube and sent to a laboratory for testing.

If fluid has built up around the lungs and is causing breathlessness, it can be drained during the VATS and you may have a pleurodesis to prevent the fluid building up again.


This is used to get a tissue sample from the lining of the abdomen (peritoneum). You will be given a general anaesthetic, then a thin tube with a light and camera will be inserted through small cuts made in your abdomen. Tissue samples can be removed through the tube and sent to a laboratory for testing.

If fluid has built up in the abdomen, it can be drained during the laparoscopy. 

CT-guided core biopsy

A CT-guided core biopsy may be used instead of VATS or laparoscopy when there is a large mass but no fluid.

You will have a local anaesthetic, and a hollow needle will be inserted through the skin to remove a thin core of tissue from the lining of the lungs or abdomen. A CT scan will be used to guide the needle into position.

You will need to lie still on a table for about 30 minutes. Afterwards you will stay in the radiology suite for a couple of hours so you can be watched for possible complications.


Draining fluid

When you first have symptoms of mesothelioma, you are likely to have a build-up of fluid in the space around your lungs or in your abdomen. Fluid around the lungs (pleural effusion) can make it hard to breathe. Fluid in the abdomen (ascites) may make it swollen and uncomfortable.

Before suggesting further tests or treatment, your doctor may drain the built up fluid to ease symptoms. When fluid is drained from the pleura, it is called a pleural tap, pleurocentesis or thoracentesis. When it is drained from the peritoneum, it is called a peritoneal tap or paracentesis. 

Draining the fluid may be done at the same time as VATS or laparoscopy. 

Less commonly used tests

  • PET scan – A small amount of radioactive glucose solution will be injected into a vein, to help cancer cells show up brighter on the scan.
  • Special stains – To confirm a diagnosis of mesothelioma, the pathologist sometimes needs to do further tests on the tissue sample using special stains. These look for specific molecules that may help to tell mesothelioma apart from other types of cancer. 

Diagnosis from fluid samples

Sometimes a fluid sample rather than a tissue sample may be used to make a diagnosis because it is easy to collect fluid when draining the pleural or peritoneal cavity. However, it can be hard to diagnose mesothelioma from fluid samples because abnormal mesothelioma cells can look similar to other cells.

To be accurate, this technique needs to be done at a specialist centre, a large volume of fluid must be collected, and the results have to be combined with information from an x-ray and CT scan. Using fluid samples for diagnosing mesothelioma may be useful if you are not well enough for a biopsy.

Staging mesothelioma

Staging is a way to describe the cancer and whether and how far it has spread beyond its original site. Doctors use particular systems when staging different types of mesothelioma. 

The staging system recommended for pleural mesothelioma is the international tumour–node–metastasis (TNM) staging system. Peritoneal mesothelioma is usually staged using the peritoneal cancer index (PCI). The higher the PCI, the further the cancer has spread.

The main test to stage mesothelioma is a CT scan. You may have had a CT scan earlier when mesothelioma was suspected, or during a CT-guided core biopsy. If that CT scan showed advanced disease, a further CT scan may not be necessary. 

Tests before surgery

If radical surgery is being considered as a suitable treatment option, you may have other scans and procedures to check whether mesothelioma has spread to other areas of the body. These may include:

  • FDG-PET scan – detects radiation from a low-level radioactive drug that is injected into the body.
  • MRI scan – uses a powerful magnet and radio waves to create detailed, cross-sectional pictures of the soft tissues in your body.
  • Endobronchial ultrasound (EBUS) – a tube with a small probe is inserted down your throat to identify lymph nodes for biopsy.
  • Surgical staging – the surgeon may remove a sample of lymph nodes and tissue from other areas of the body. This is only done for pleural mesothelioma.



Mesothelioma behaves differently in different people. It is often present for many months before being diagnosed at an advanced stage, which will affect prognosis. After diagnosis, mesothelioma may progress quickly or more slowly. If it progresses slowly, some people may live for several years or longer.

Your doctor will consider several factors when discussing prognosis with you, including:

  • the type of mesothelioma cell
  • the stage
  • the type of treatment you are able to have
  • your symptoms, such as weight loss or pain
  • your blood count – people with normal levels of blood cells usually have a better prognosis
  • your overall health – recovering quickly after procedures tends to suggest a better outcome.

While knowing the stage helps doctors plan treatment, it is not always useful for working out prognosis for people with mesothelioma. This is partly because it is hard to predict how quickly mesothelioma will grow.

In general, the earlier cancer is diagnosed, the better the outcome. If the cancer has advanced to a point where it is difficult to treat successfully, the priority will be to relieve symptoms and improve your quality of life.

Understanding Mesothelioma

Download our Understanding Mesothelioma booklet learn more.

Download now  



Expert content reviewers:

A/Prof Brian McCaughan, Cardiothoracic Surgeon, Chris O’Brien Lifehouse, NSW; Theodora Ahilas, Principal Lawyer, Maurice Blackburn Lawyers, NSW; Prof David Ball, Director, Lung Service, Peter MacCallum Cancer Centre, VIC; Shirley Bare, Consumer; Cassandra Dickens, Clinical Nurse Consultant, Cancer Care Coordinator – Thoracic Malignancies, Sunshine Coast University Hospital, QLD; Penny Jacomos, Social Worker, Asbestos Diseases Society of South Australia, SA; A/Prof Thomas John, Medical Oncologist, Senior Clinical Research Fellow, Austin Health, and Olivia Newton-John Cancer Research Institute, VIC; Victoria Keena, Executive Officer, Asbestos Diseases Research Institute, NSW; Penny Lefeuvre, Consumer; Jocelyn McLean, Mesothelioma Support Coordinator, Asbestos Diseases Research Institute, NSW; Prof David Morris, Peritonectomy Surgeon, St George Hospital and University of New South Wales, NSW; Caitriona Nienaber, 13 11 20 Consultant, Cancer Council Western Australia; Prof Anna Nowak, Medical Oncologist, Sir Charles Gairdner Hospital, and Professor of Medicine, School of Medicine and Pharmacology, The University of Western Australia, WA; Prof Jennifer Philip, Palliative Care Specialist, St Vincent’s Hospital, Peter MacCallum Cancer Centre and Royal Melbourne Hospital, VIC; Nicole Taylor, Acting Lung Cancer and Mesothelioma Cancer Specialist Nurse, The Canberra Hospital, ACT.

Page last updated:

The information on this webpage was adapted from Understanding Mesothelioma - A guide for people with cancer, their families and friends (2019 edition). This webpage was last updated in August 2021.

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