Mesothelioma is a rare type of cancera disease where abnormal cells split without control and spread to other nearby body tissue and/or organs that develops in the lining of internal organs. More specifically, they develop from mesothelial cellsthe basic structural and functional unit of all living things, 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 tissuea group of cells that work together to perform a function 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 pleuraa thin layer of tissue covering the lungs and the wall of the interior chest cavity. 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 effusionabnormal fluid build-up in the pleural space, which can cause chest pain and breathing difficulties). 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 prognosisto predict how a disease/condition may progress and what the outcome might be.
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 peritoneumthe membrane that lines the abdominal cavity. The peritoneum has an inner layer (visceral peritoneum) that lines the surface of the organs such as the bowelportion of the digestive system that digests food (small bowel) and absorbs salts and water (large bowel); also called intestines, 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, metastasiswhen the cancer has spread to other parts of the body, also known as mets, and how the cancer cells look under the microscope. Stagingthe process of determining how big the cancer is, where it started and if it has spread to other areas 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 tumoura tissue mass that forms from groups of unhealthy cells will be staged and graded to help determine the best treatment option for you.
Treatment options for pleural mesothelioma may include:
- Chemotherapya cancer treatment that uses drugs to kill or slow the growth of cancer cells, while minimising damage to healthy cells.
- Radiation therapya treatment that uses controlled doses of radiation to damage or kill cancer cells.
- Surgerytreatment involving removal of cancerous tissue and/or tumours and a margin of healthy tissue around it to reduce recurrence, potentially including:
- Extrapleural pneumonectomyremoval of the diseased lung, part of the pericardium (membrane covering the heart), part of the diaphragm and part of the parietal pleura (EPP).
- Pleurectomy and decorticationcomplete or partial removal of the pleura, as well as removal of visible tumours (P/D).
- Clinical trialsresearch studies performed to test new treatments, tests or procedures and evaluate their effectiveness on various diseases.
- Palliative carea variety of practices and exercises used to provide pain relief and improve quality of life without curing the disease.
Treatment options for peritoneal mesothelioma may include:
- Surgery, most commonly a peritonectomyremoval of the peritoneum.
- Chemotherapy, potentially including:
- Hyperthermic intraperitoneal chemotherapy (HIPEC)an aggressive type of chemotherapy that involves applying chemotherapy that has been heated to 42 degrees Celcius to the abdominal cavity to kill cancer cells that may remain after tumour removal; often performed alongside cytoreductive surgery.
- Early postoperative intraperitoneal chemotherapy (EPIC)an aggressive type of chemotherapy that involves applying chemotherapy directly into the abdominal cavity shortly after surgery to kill cancer cells that may remain after tumour removal; often performed alongside cytoreductive surgery.
- Normothermic intraperitoneal chemotherapy (NIPEC)an aggressive type of chemotherapy that involves applying chemotherapy at room-temperature to the abdominal cavity to kill cancer cells that may remain after tumour removal; often performed alongside cytoreductive surgery.
- Clinical trials.
- Palliative care.
Risk factors
The biggest and only known riskthe possibility that something bad will happen 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.
Symptoms
The symptoms of mesothelioma may vary, depending on where in the body it has formed.
Early symptoms of pleural mesothelioma may include:
- Dyspneadifficulty breathing, shortness of breath, which may be worse when lying down.
- Pain under the rib cage, in the side of the chest or in the abdomenstomach, stomach area, belly, which may be worse when breathing in deeply.
- Persistent cough.
- A massa growth of cells that come together to make a lump, may or may not be cancer under the skin in the chest.
- Extra sensitive skin or changes in skin sensation.
- Fever.
- Unexplained weight loss.
- Fatiguea state of extreme tiredness or exhaustion, can be physical or mental.
- Excessive sweating.
Early symptoms of peritoneal mesothelioma may include:
- Loss of appetite/changes in eating habits.
- Nauseato feel sick or likely to vomit 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
If your doctor suspects you have a mesothelioma, they may order the following tests to confirm the diagnosisthe process of identifying a disease based on signs and symptoms, patient history and medical test results and refer you to a specialist for treatment:
- Physical examinationan examination of your current symptoms, affected area(s) and overall medical history.
- Imagingtests that create detailed images of areas inside the body tests, potentially including:
- Chest x-raya type of medical imaging that uses x-ray beams to create detailed images of the body .
- CT (computed tomography) scana type of medical imaging that uses x-rays and computer technology to create detailed images of the body.
- Blood teststesting done to measure the levels of certain substances in the blood.
- Thoracentesisa procedure that drains the fluid from your lungs using a needle.
- Biopsyremoval of a section of tissue to analyse for cancer cells.
