It is often difficult to diagnose Mesothelioma but if a GP suspects that a patient may be suffering from the disease they should follow cancer referral guidelines, which were issued in 2000, and refer the patent to a specialist consultant. If the GP considers it urgent an appointment with a consultant should take place within two weeks of a referral and tests should be arranged to help the diagnosis.
Scans
To help find out if, and how far, the Mesothelioma has developed, a patient will often have a Computed Tomography (CT) scan or they may need to have a Magnetic Resonance Imaging (MRI), Ultrasound Scan (USS) or a Positron Emission Tomography (PET) scan.
CT scan
This is an x-ray examination that is carried out by an x-ray specialist called a radiographer. It involves lying on a scan table, usually between 10 and 30 minutes, to allow the scanner to takes detailed pictures of a cross section of the inside of the body. Often patients who have a CT scan are given a drink or injection about an hour before the scan, to allow particular areas of the body to be seen more clearly. The pictures taken from the scan will then be given to a radiologist (specialised X-ray doctor) and the results will then be sent to the consultant who requested the scan.
MRI scan
This is similar to a CT scan but an MRI scan uses a powerful magnet and a computer to produce detailed images of any part of the body.
As with a CT scan the patient will need to lie on the scanner table for approximately 20 to 40 minutes while the table is then moved into the magnet. A tapping sound will be heard while the scan takes place. In some cases a colourless liquid, that shows up on the scan, may also be injected into a vein of the patient to show more information on the scan. A radiologist will then study MRI scan pictures and give his/her results to the consultant who requested the scan.
Ultrasound scan
An ultrasound scan produces high frequency sound waves which then allow images of organs and blood vessels in the body to be reflected and seen on a television screen.
The patient has to lie on a table for approximately 15 minutes while a warm gel is placed on the skin in the area to be investigated. An ultrasound probe is then passed over the skin.
The scan pictures will be studied by a radiologist or a sonographer who will then send the results to the consultant who requested the scan.
PET scan
This is a new type of scan that is often only available in specialist centres but it measures the activity of cells in different parts of the body. A very small amount of a mildly radioactive ‘sugar’ is injected into a vein, usually in the arm, and then a scan is taken. Areas of cancer absorb more radioactive substances than normal tissue in the body so it helps to show them up on the scan. Results of the scan will be sent to the consultant for his/her consideration.
Although scans and x-rays can help in the diagnosis of Mesothelioma to make a more definite diagnosis it is often necessary for a pathologist to assess the cells and tissues that are being affected by the disease. He/she will look for changes in the tissue or cell sample and may conduct tests on them under a microscope to see how they react. This will help to confirm if Mesothelioma is present and how it is affecting the body.
If there is fluid in the areas where the Mesothelioma is suspected to be, usually near the chest wall or in the abdomen, this can assessed by the pathologist. The fluid can be either drawn into a syringe from the patient or a drain inserted to allow for fluid to be removed slowly over a few days. A sample of the fluid will then be taken for analysis.
Biopsy
Where a pathologists needs to analyse cells and tissues from the affected areas of the body, it is necessary to remove small sections of these from the patient. This is called a biopsy. There are a variety of methods that can be used to do this.
Sometimes the biopsy is done whilst a patient is having a scan because the scanning equipment will guide the doctor to the affected part of the pleura or peritoneum.
Sometimes a thoracoscopy or a Video Assisted Thoracoscopic Surgery (VATS) is performed to allow a biopsy to be performed. A thoracoscopy is conducted under a local anaesthetic and allows a small camera telescope to be inserted through a single 1-2 cm cut in the patient from which a biopsy can be taken.
Alternatively VATS can be performed under general anaesthetic to allow a larger biopsy to be taken and a better assessment of the area affected.
As any biopsy has to be fully analysed, it can take several days for results to be found and will often need the pathologist to confirm a diagnosis of Mesothelioma. In some cases, however, even when tests are carried out it may still be difficult to confirm a diagnosis.
Staging Mesothelioma
Once tests are carried out, and a diagnosis confirmed, specialists will also be able to know more about the size and position of the cancer and if it appears to have spread to nearby tissues or to other, more distant, areas of the body. This is often known as the ‘staging’ process.
This information can be helpful in finding out how much the patient is affected by the disease and, in making recommendations for treatment. It will also help, in the future, to assess how effective any treatment has been.
There are different ways that Mesothelioma can be staged but often hospitals follow the International Mesothelioma Interest Group (IMIG) staging system which, following tests, categorises the disease as follows:
STAGE 1 Disease limited to the pleura only on one side of the chest.
STAGE 2 Disease limited to the pleura on one side of the chest but the cancer cells have extended from the pleura into the underlying lung tissue or muscle of the diaphragm.
STAGE 3 The cancer has either spread beyond the pleura to glands in the chest and/or has advanced deeper into the tissues surrounding the pleura.
STAGE 4 The cancer has spread to distant organs or tissues or invaded deeply into tissues close to the pleura e.g. across the diaphragm into the abdomen, into the pleura of the opposite lung or into the spine or heart muscle.