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How is mesothelioma diagnosed?

Initial stages

It is not always easy to diagnose mesothelioma as some of the initial symptoms can be quite vague and general, such as tiredness, weight loss, shortness of breath and chest pain.  

Visiting a GP

When you visit your GP they will carry out an examination and take a history. Your GP may tap your chest and use a stethoscope.  They will be looking for any signs of fluid collecting on the lungs and reduced chest expansion.

Your GP might refer you to a hospital for a chest x-ray or sometimes, directly to a specialist lung doctor (a respiratory physician).

Seeing specialist doctors at the hospital

Your specialist may have received preliminary information from your GP as well as x-ray and scan results, if they have already been carried out.  They will typically examine you, ask about your medical history and symptoms and may ask about previous occupations and whether you might have been exposed to asbestos.  Other tests may be arranged such as routine blood tests and breathing tests to measure how your lungs function.


You will almost always be asked to have a chest or abdominal x-ray at an early stage to look for abnormalities.  An abdominal x-ray may show if there is any fluid or swelling in the abdomen, and a chest x-ray can show if there is fluid known as a pleural effusion in the lungs.  There are various causes of pleural effusion so the presence of fluid does not mean that a diagnosis of mesothelioma will follow.  A diagnosis of mesothelioma can often only be confirmed after further tests have been carried out.

CT scans

A CT scan is a computerised scan using x-rays that takes detailed pictures of a cross section of the inside of the body.  CT stands for computed tomography.  It shows a lot more detail than a normal x-ray, and may be carried out on the chest or abdomen. You may be given an injection of a dye called a contrast before the scan is performed.  This makes the scan easier to read.  The hospital will provide information about the CT scan such as how long it will take, how long you should avoid eating and drinking for before the scan, etc.

The CT scan pictures will be looked at by a doctor called a radiologist who specialises in reporting on x-rays and scans.  The radiologist will write a report and send this to the specialist doctor who originally asked for the scan to be carried out.  Sometimes a CT scan will be used when a biopsy is carried out.

Ultrasound scan

This is a scan of internal organs and/or blood vessels using a probe that produces high frequency sound waves.  A warm gel will be applied to the skin and a probe used to take images which can be seen on a television screen.  An ultrasound of the abdomen will usually be needed to show up fluid in the tummy.  The results will be interpreted by a radiologist or sonographer who will send the information to the consultant who asked for the scan.

MRI scan

An MRI (magnetic resonance imaging) scan is similar to a CT scan.  A contrast agent (a colourless liquid that can be seen on the scan) may be used.  The scan involves using a powerful magnet to produce very detailed images on a computer.  Again, the results will be sent by the radiologist to the specialist doctor who requested the scan.

PET scan

A PET (positron emission tomography) scan uses a very small amount of a low dose radioactive contrast agent to show up areas of the cancer. PET scans are relatively new and the patient may have to travel to a specialist centre for the scan to be performed.  They may be combined with a CT scan to make them more accurate.

Pathology tests

X-rays and scans (known as radiology) provide very important evidence to try to reach a correct diagnosis.  However, what is known as pathological evidence will usually be necessary to establish a firm diagnosis.  Pathology means tests which involve a specialist doctor (a pathologist) analysing fluid and tissue samples by looking at them with a microscope and using special chemicals.  These tests are known as staining and will usually be carried out to establish a diagnosis of mesothelioma.   

Pleural or peritoneal fluid

Fluid can build up in the pleura (pleural effusion) or peritoneum (ascites) due to inflammation.  This can cause breathlessness and in cases of peritoneal mesothelioma can make the abdomen feel swollen and uncomfortable.  A procedure called pleural or peritoneal aspiration can be preformed to provide relief and enable a pathologist to analyse the fluid to look for cancer cells.  The fluid may be drawn off using a syringe and a drain may be fitted to allow the fluid that accumulates to be removed slowly through a tube.

Analysis of the fluid (known as cytology) may not always lead to the detection of mesothelioma cells and typically in the majority of cases, a biopsy will be carried out.


A biopsy is the removal of a piece of tissue in order to reach a diagnosis.  It is usually necessary for a sample of tissue to be taken from the pleura or peritoneum to enable a pathologist to identify mesothelioma cells and lead to a diagnosis of mesothelioma.  There are different ways that samples can be taken.  The amount of tissue that is removed varies and might be removed as part of a thin core of tissue, a large section or a lump.

A biopsy with a scan/fluid drainage

A biopsy can be carried out while you are undergoing a scan, or when drainage is being performed.  The scanning equipment may help to better identify the areas of the pleura or peritoneum that are affected.

However, mesothelioma can be a difficult illness to diagnose.  It may be difficult for the pathologist to decide if the cells or tissue are a type of mesothelioma or not.  The cells can look similar to other types of cancer such as lung cancer in the case of pleural mesothelioma.  Therefore, it is often necessary for you to undergo a surgical biopsy.   

Thoracoscopy/video assisted thoracoscopic surgery (VATS)

A thoracoscopy is a small operation carried out under either local or general anaesthetic by a specialist when a flexible tube with a video and light attached (a thoracoscope) is passed through a small cut (usually about 1-2 cm) in the chest wall.  

An ultrasound or CT scan may be used to position the needle correctly. The doctor will then take a sample from the pleura.  This procedure may require a short stay in hospital for the patient.


A laparoscopy will be carried out to try to diagnose peritoneal mesothelioma.  It involves a small operation whereby a doctor puts a tube with a camera and light into your abdomen through a small cut.  It might be carried out under local or general anaesthetic and the doctor will look for any sign of cancer and take biopsies.  Sometimes more than one surgical cut will be necessary.

The results

The biopsy samples will be sent off to a laboratory for tests to be carried out.  Sometimes the samples will be sent to a specialist pathologist in another hospital for a second opinion.  It may take a few weeks sometimes before the results are available, particularly if the samples have to be sent off to another hospital for a second opinion. This will obviously be a very anxious time.  The doctor will ask you to come back to the hospital when the results are available and will discuss the findings, the diagnosis and possible treatments.

To assist in reaching a diagnosis hospitals have teams of experts called multi-disciplinary teams (MDT’s).  They consist of specialist health professionals with different areas of expertise who regularly meet to discuss whether they believe the diagnosis is correct, the stage of the disease and possible treatments.

Staging mesothelioma

If mesothelioma has been diagnosed then it will be helpful to find out what stage the illness is at.  This is known as staging and will describe the size and position of the tumour and whether it has spread to lymph nodes or other parts of the body.  Working out the stage is helpful because it will assist the doctors in making decisions about possible treatment, although it may not be easy for the stage to be calculated precisely.

The system that is used in the UK for pleural mesothelioma is the International Mesothelioma Interest Group (IMIG) staging system with stage 4 being the most advanced stage and stage 1 the least advanced.

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