Mesothelioma is a rare type of cancer that develops in the lining of internal organs. More specifically, they develop from mesothelial cells, which form a protective layer called the mesothelium.
Mesothelioma is generally caused by exposure to asbestos, which is a group of naturally occuring heat-resistant silicate minerals. Asbestos occurs naturally in the environment, and was a major component of building and construction materials, insulation, floor tiles, roofing, textured paint and textiles until late 1980s, and car products until 2003. Asbestos fibres are incredibly thin, and can become trapped in the lungs if inhaled and cause damage over time. Although asbestos-containing products were banned from production in 2003, many buildings and construction materials are still in place that may contain asbestos. Mesothelioma is often diagnosed after 20-60 years after exposure.
Mesothelioma is more common in males, and is generally diagnosed over the age of 65. However, anyone can develop this disease.
Types of Mesothelioma
Mesothelioma can also be classified by their cellular appearance under the microscope. The main distinguishable cell types include:
- Epithelioid cells, which are the most common type and resemble normal mesothelial cells.
- Sarcomatoid cells, where cancerous cells don’t look like normal mesothelial cells and look like cells from cells from fibrous tissue instead.
- Mixed or biphasic, where cancer cells have a combination of both types of cells.
Mesothelioma can also be classified by the location they are found in. Using this classification, there are two main types of mesothelioma, as well as some incredibly rare types.
Pleural Mesothelioma
Pleural mesothelioma is the most common form of mesothelioma. It develops in the mesothelium that covers each lung, called the pleura. The pleura has an inner layer (visceral pleura) that lines the lung surface, and an outer layer (parietal pleura), that lines the diaphragm and chest cavity. The pleural cavity fills the space between the two pleural layers, and allows these layers to slide over each other when we breathe. When asbestos fibres are inhaled, they may become trapped in either of the pleural layers, which causes these layers to thicken and excess liquid may collect in the pleural cavity (pleural effusion). This may result in a reduction in the amount the lung can expand, which could cause difficulties breathing. Pleural mesothelioma is often aggressive and tends to have a poor prognosis.
Peritoneal Mesothelioma
Peritoneal mesothelioma is the second most common form of mesothelioma. It develops in the mesothelium that lines the organs of the abdominal cavity, called the peritoneum. The peritoneum has an inner layer (visceral peritoneum) that lines the surface of the organs such as the bowel, the ovaries and the liver, and an external layer (parietal peritoneum) that lines the walls of the abdominal cavity and the pelvis. The peritoneal cavity lines the space between the two layers, and allows these layers to slide over each other when we move. When asbestos fibres are inhaled or ingested, they may become trapped in either of the peritoneal layers, which causes these layers to thicken and excess fluid may collect in the peritoneal cavity (peritoneal effusion). The effects of peritoneal mesothelioma may vary depending on location. This form of mesothelioma is often aggressive and tends to have a poor prognosis.
Other forms of Mesothelioma
Other forms of mesothelioma are incredibly rare, and include pericardial mesothelioma, where mesothelioma develops in the mesothelial layer lining the heart, and testicular mesothelioma, where mesothelioma develops in the mesothelial layer lining the testicles and tunica vaginalis.
Treatment
If mesothelioma is detected, it will be staged and graded based on size, metastasis (whether the cancer has spread to other parts of the body) and how the cancer cells look under the microscope. Staging and grading helps your doctors determine the best treatment for you.
Treatment is dependent on several factors, including location, stage of disease and overall health. In adult patients, your tumour will be staged and graded to help determine the best treatment option for you.
Treatment options for pleural mesothelioma may include:
- Chemotherapy.
- Radiation therapy.
- Surgery, potentially including:
- Extrapleural pneumonectomy (EPP) (removal of the affected lung, part of the pericardium (membrane covering the heart), part of the diaphragm, and part of the parietal pleura).
- Pleurectomy decortication (PD) (removal of the pleura of the lungs).
- Clinical trials.
- Palliative care.
Treatment options for peritoneal mesothelioma may include:
- Surgery - Peritonectomy.
- Chemotherapy, potentially including:
- Heated intraoperative intraperitoneal chemotherapy (HIPEC).
- Early postoperative intraperitoneal chemotherapy (EPIC).
- Normothermic (normal temperature) intraperitoneal chemotherapy (NIPEC).
- Clinical trials.
- Palliative care.
For more information on the treatment options, please refer to the Rare Cancers Australia Treatment Options page.
Risk factors
The biggest and only known risk factor for mesothelioma is exposure to asbestos. However, in some cases, people who develop mesothelioma have had no clear exposure to asbestos, which suggests there are other unknown risk factors for this disease.
Not everyone who has been exposed to asbestos will develop the disease. See your general practitioner (GP) if you are concerned.
Early symptoms
The symptoms of mesothelioma may vary, depending on where in the body it has formed.
Early symptoms of pleural mesothelioma may include:
- Shortness of breath, which may be worse when lying down.
- Pain under the rib cage, in the side of the chest or in the abdomen, which may be worse when breathing in deeply.
- Persistent cough.
- A mass under the skin in the chest.
- Extra sensitive skin or changes in skin sensation.
- Fever.
- Unexplained weight loss.
- Fatigue.
- Excessive sweating.
Early symptoms of peritoneal mesothelioma may include:
- Loss of appetite/changes in eating habits.
- Nausea and/or vomiting.
- Night sweats.
- Fever.
- Fatigue.
- Unexplained weight loss.
- Abdominal pain and/or vomiting.
- Bowel or urinary problems.
Not everyone with the symptoms above will have cancer, but see your GP if you are concerned.
Diagnosis/diagnosing
If your doctor suspects you have a mesothelioma, they will order a range of diagnostic tests to confirm the diagnosis, and refer you to a specialist for treatment.
Physical examination
Your doctor will collect your overall medical history, as well as your current symptoms. Following this, they may examine your body to check for any abnormalities.
Imaging and blood tests
The doctor will take images of your body using magnetic resonance imaging (MRI), a computed tomography scan (CT scan), x-ray and/or ultrasound, depending on where it is suspected the cancer is. The doctor may also look at other parts of the body and looks for signs of metastasis. Additionally, a blood test may be taken to assess your overall health and help guide treatment decisions.
Biopsy
Once the location of the cancer has been identified, the doctor will perform a biopsy to remove a section of tissue using a needle. Once a sample has been removed, it will be sent to a lab and analysed for cancer cells.
Prognosis (Certain factors affect the prognosis and treatment options)
While it is not possible to predict the exact course of the disease, your doctor may be able to give you a general idea based on the rate and depth of tumour growth, susceptibility to treatment, age, overall fitness, and medical history. Generally, early-stage mesotheliomas have a better prognosis and survival rates. However, if the cancer is advanced and has spread, the prognosis may not be as good and there may be a higher risk of cancer recurrence. It is very important to discuss your individual circumstances with your doctor to better understand your prognosis.
Mesothelioma support services
A cancer diagnosis can be difficult and overwhelming for you and your family, and may affect your emotional and mental health. Support services can help dealing with your diagnosis, connect with others with mesothelioma, provide access to professional support, and potentially improve emotional wellbeing and mental health. In some cases, Mesothelioma patients may also be entitled to compensation.
For more information on support services available to you, please refer to the Australian Mesothelioma Registry.
References
Some references are to overseas websites. There may be references to drugs and clinical trials that are not available here in Australia.