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.
The path to diagnosis usually begins with seeing your GP or going to a hospital emergency room, perhaps for shortness of breath, pain or another symptom. The doctor will examine you and take a history of your general health. If you think you may have been exposed to asbestos in the past, it is important to raise it at this time as many doctors won't automatically look for mesothelioma. The doctor will arrange some initial tests and probably refer you to a specialist, usually a respiratory physician (for chest symptoms) or a gastroenterologist (for abdominal symptoms).
You are likely to have quite a few tests and see several different health professionals before a diagnosis of mesothelioma is confirmed.
General tests
Blood tests and x-rays can provide information about your overall health and help to rule out other conditions.
Blood test
You will have blood taken to check your overall health and let your doctors know how your blood cells, liver and kidneys are working. This helps them judge your fitness for treatment. A blood test will not usually show up mesothelioma, but can sometimes reveal certain markers that suggest the presence of the disease.
X-ray
If pleural mesothelioma is suspected, you will have a chest x-ray to look for any abnormalities 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 abnormalities in the abdomen, such as fluid and thickening in the peritoneum.
If abnormal growth or other changes are found, you will need more tests to check whether mesothelioma or another condition is the cause. Sometimes mesothelioma will not show up on an x-ray but can be seen in a CT scan.
Waiting for test results
Waiting for test results can be a difficult time. It's common to feel anxious about what will happen if you do have mesothelioma. It may help to focus on recovering from the test procedures and any improvements in symptoms.
Some results are available within a few days, but others take several weeks. In some cases, it may be necessary to have more tests before a definitive diagnosis can be made. Ask your doctor or nurse how long the test results will take. It may help to talk to a family member or friend about how you're feeling. They're probably experiencing similar emotions.
If you need support or want to learn more about what a mesothelioma diagnosis will mean for you, call Cancer Council 13 11 20 or contact one of the organisations listed here.
CT scan
A CT (computerised tomography) scan uses x-rays and a computer to create a detailed picture of an area inside the body.
Before the scan, you will be given an iodine contrast dye to make the scan pictures clearer. This is usually injected into a vein in your arm, but is sometimes given as a drink. If you have had an allergic reaction to iodine or dyes during a previous scan, tell your medical team beforehand. Also let them know if you have diabetes or kidney problems or are pregnant.
For the scan, you will need to lie flat on a table that slides in and out of a large, doughnut-shaped scanner. The procedure takes about 30 minutes. Although the test itself is painless, lying flat and still can be uncomfortable if you already have breathlessness or pain. Discuss any concerns with your medical team.
The CT scan provides accurate information about 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 gathered by the CT scan is used to work out the best way of obtaining tissue for testing (see Biopsy below).
Biopsy
A biopsy is the main test used to diagnose mesothelioma. A doctor will remove a sample of tissue for a specialist called a pathologist to examine under a microscope. The pathologist can then determine if the tumour is mesothelioma and, if so, the type of mesothelioma cells present. Mesothelioma is usually classified according to the appearance of the cells (although in about 25% of cases, no classification has been recorded):
- Epithelioid – cells look similar to normal mesothelial cells. This is the most common type, making up about 50% of cases.
- Sarcomatoid – cells have changed and look like cells from fibrous tissue. This type accounts for about 13% of cases.
- Mixed or biphasic – has epithelioid and sarcomatoid cells. This type makes up about 12% of all cases.2
Obtaining a biopsy for diagnosis can be challenging, so a respiratory physician or gastroenterologist, radiologist, surgeon and pathologist may all be involved.
Ways to take a biopsy for mesothelioma
A biopsy can be taken in different ways. Keyhole surgery, such as VATS or laparoscopy, is usually the preferred biopsy technique as several tissue samples can be taken and fluid can be removed. However, the choice will depend on your general health and fitness, and how suitable the tumour is for sampling using this method. An alternative method is CT-guided core biopsy.
Video-assisted thoracoscopic surgery (VATS)
To get a tissue sample from the lining of the lungs (pleura), your doctor may suggest VATS. You will be given a general anaesthetic, then a thin tube with a light and camera will be inserted through several small cuts in your body. Tissue samples can be removed through the tube and sent to a laboratory for analysis. If fluid has built up around the lungs and is causing breathlessness, it can be drained during the VATS.
Laparoscopy
To get a tissue sample from the lining of the abdomen (peritoneum), your doctor may suggest a laparoscopy. You will be given a general anaesthetic, then a thin tube with a light and camera will be inserted through small cuts on your abdomen. Tissue samples can be removed through the tube and sent to a laboratory for analysis. Fluid that has built up in the abdomen can be drained during the laparoscopy.
CT-guided core biopsy
A CT-guided core biopsy may be used instead of VATS or laparoscopy. You will have a local anaesthetic and the biopsy will be taken from the lining of the lungs or abdomen with a needle that has a tip for cutting out tissue. A CT scan will be used to guide the needle into position.
During a CT-guided core biopsy, 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 potential complications (such as bleeding or a collapsed lung).
Special stains
Sometimes to confirm a diagnosis of mesothelioma, the pathologist needs to do further tests on the tissue sample using special stains. These look for specific molecules that may help to distinguish mesothelioma from other cancers.
Draining fluid
When you first experience symptoms of mesothelioma, there is likely to be 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 cause abdominal swelling, shortness of breath and pain.
Your doctor may drain some fluid to provide relief before suggesting further tests or treatment. A sample of the fluid may be sent to a laboratory for testing to see whether cancer cells are present or whether the effusion is caused by another disease.
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. To prevent fluid building up around the lungs again, you may have a talc pleurodesis at the same time. Read more about these procedures.
Other ways to diagnose mesothelioma
The current clinical practice guidelines recognise that the diagnosis of pleural mesothelioma can be difficult. They recommend CT scan and a biopsy guided by VATS or CT as the most reliable tests. The following techniques are considered less reliable for diagnosing this disease and are not recommended:
- fine needle aspiration, which uses a fine needle to extract sample of cells
- core biopsy (using a needle to remove a sample of tissue)without the guidance of a scan, such as a CT or ultrasound.
Diagnosis from fluid samples
In some cases, a fluid sample rather than a tissue sample may be used to make a diagnosis because it's easy to collect fluid when draining the pleural or peritoneal cavity. However, it can be harder to diagnose mesothelioma with fluid samples, especially as abnormal mesothelioma cells can look similar to cells found in other conditions.
Some specialist centres have developed a high level of expertise in diagnosing mesothelioma using fluid samples. For this method to provide a reliable diagnosis, it's important that the tests are done at a specialist centre, a large volume of fluid has been collected, and the results are combined with information from an x-ray and CT scan. Your doctors may suggest this method of diagnosing mesothelioma if you are not well enough for a biopsy.
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