What is Mesothelioma?
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A mesothelioma is a rare form of cancer that affects the cells that make up the mesothelium. The mesothelium is the lining or membrane that covers and protects various internal organs of the body.
ALL YOU NEED TO KNOW ABOUT MESOTHELIOMA SURVIVAL RATEÂ
The mesothelium is composed of two layers of specialized cells known as mesothelial cells. One layer directly surrounds an organ; the other forms a protective sac around thoracic and peritoneal organs.
The most common form of mesothelioma affects the pleura, which is the membrane or sac that lines the lungs and chest cavity. Other, rarer types of mesothelioma affect tissue in the abdomen (peritoneal mesothelioma), around the heart and around the testicles.
Mesothelioma doesn't include a form of noncancerous (benign) tumor that occurs in the chest and is sometimes called benign mesothelioma or solitary fibrous tumor.
Mesothelioma is an aggressive and deadly form of cancer. Mesothelioma treatments are available, but for many people with mesothelioma, a cure is not possible. Symptoms of mesothelioma may not appear until up to 30 to 50 years after initial exposure to asbestos.
However, after symptoms become apparent, mesothelioma may rapidly progress to cause life-threatening complications.
In 2015, the fatality rate for mesothelioma in the United States (U.S.) was 10.93 per million people. Only 9 per cent of those diagnosed with mesothelioma live longer than 5 years.
The term "cancer" refers to a group of diseases characterized by abnormal, uncontrolled cellular growth (e.g., mesothelial cells) that invades surrounding tissues and may spread (metastasize) to distant bodily tissues or organs via the bloodstream, the lymphatic system, or other means.
There are three types of mesothelioma:
- Pleural mesothelioma is the most common form. It affects the pleura or the lining around the lungs.
- Peritoneal mesothelioma is the second most common form. It attacks the lining of the abdomen, called the peritoneum.
- Pericardial mesothelioma is the rarest form. It affects the protective layer of the heart.
Symptoms of Mesothelioma
It can take up to 30 years for symptoms to show after exposure to asbestos particles and dust. Diagnosis often happens when the disease is already advanced. The outcome depends on how early the malignancy can be diagnosed.
The main symptoms of mesothelioma of the lungs are shortness of breath and chest pain. Accumulation of fluid in the pleura caused by the mesothelioma, if sufficiently large, may also contribute to the shortness of breath.
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Pleural mesothelioma can be indicated by:
- shortness of breath
- coughing, often painful
- unexpected and unexplained weight loss
- pain under the ribcage
- detectable lumps under the skin in the chest area
- lower back pain
- discomfort in the side of the chest
- exhaustion
- sweating
- fever
- difficulty swallowing
Peritoneal mesothelioma can involve:
- unexplained weight loss
- abdominal pain
- swelling in the abdomen
- lumps in the abdomen
- nausea and vomiting
Pericardial mesothelioma causes:
- low blood pressure
- shortness of breath
- fluid retention, or edema, often in the legs
- heart palpitations
- extreme fatigue following light exertion
- chest pain
Causes of Mesothelioma
The main risk factor for mesothelioma is working with asbestos. Asbestos is a group of minerals with thin microscopic fibers. Because these fibers are resistant to heat, fire, and chemicals and do not conduct electricity, asbestos has been mined and used widely in the construction, automotive, and other industries. Asbestos is made of silicon, oxygen and some other elements.
Asbestos is used in a range of products, especially building materials, including siding, floor tiles, ceiling materials, and roof shingles. Its presence is also found in friction products, such as brake parts, as well as heat-resistant fabrics, packaging, coatings, and gaskets.
If tiny asbestos fibers are released into the air, as they are in the manufacturing process, they can be inhaled or swallowed, leading to serious health problems. They can then be inhaled or swallowed and become permanently lodged in the lungs, for decades in some cases. Other organs can also be affected.
Risk factors for Mesothelioma
Factors that may increase the risk of mesothelioma include:
- Personal history of asbestos exposure. If you've been directly exposed to asbestos fibers at work or at home, your risk of mesothelioma is greatly increased.
- Living with someone who works with asbestos. People who are exposed to asbestos may carry the fibers home on their skin and clothing. Exposure to these stray fibers over many years can put others in the home at risk of mesothelioma. People who work with high levels of asbestos can reduce the risk of bringing home asbestos fibers by showering and changing clothes before leaving work.
- A family history of mesothelioma. If your parent, sibling or child has mesothelioma, you may have an increased risk of this disease.
Even family members who have never entered an asbestos-rich environment can be exposed. Workers exposed to asbestos can accidentally carry fibers home in their clothing, and become inhaled by other members of the household.
The World Health Organization (WHO) said that approximately 125 million people globally were exposed to asbestos at work in 2005, despite their employers having known about the link to cancer and other lung diseases for over six decades. Most work-related exposure today occurs in developing nations.
In much rarer cases, mesothelioma may be linked to:
- irradiation
- inhalation of fibrous silicates such as erionite, zeolite and intrapleural thorium dioxide
Mesothelioma Diagnosis Tests
There are several different types of mesothelioma tests. These include:
Blood Tests. Blood levels of 3 substances -- fibulib-3, osteopontin, and soluble mesothelin-related peptides (SMRPs) -- are often elevated in people with mesothelioma. Although these blood tests cannot confirm a diagnosis of mesothelioma, high levels of these substances make mesothelioma more likely.
This test goes by different names, depending on where the fluid is:
- Thoracentesis -- chest cavity
- Paracentesis -- abdomen
- Pericardiocentesis -- membrane around the heart
  The doctor will ask about personal and family medical history and conduct a physical examination. They will also ask about previous employment if mesothelioma is suspected, to assess any potential exposure to asbestos. Even if your doctor does not find mesothelioma cells in a fluid, that doesn't necessarily mean you don't have mesothelioma. Sometimes samples of actual tissue (biopsies) are needed to diagnose mesothelioma.
Biopsy
A biopsy can confirm the diagnosis. The type of biopsy depends on where the symptoms are.
In the chest or abdominal area: The doctor will use a fine-needle aspiration. A small needle is inserted into the abdomen and chest to remove and test some fluid or piece of tissue.
In the chest area only: The doctor will run a thoracoscopy. A thoracoscope is inserted through a small incision between the patient's ribs. A thoracoscope is a tube with a small camera at the end, designed for examining the chest cavity. The surgeon then removes a piece of tissue.
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Needle Biopsy. This procedure involves inserting a long, hollow needle through the skin to remove a tiny piece of a tumor. Your doctor may use imaging tests to guide the needle into the tumor. In some cases, the sample may be too small to make a diagnosis and a more invasive procedure is needed.
Thoracotomy
In a thoracotomy, the surgeon opens the chest between the ribs to see the target area and check for signs of cancer. Some tissue may be removed for testing in the laboratory.
 In these procedures, the doctor inserts a thin, lighted scope through a small incision in the skin to see potential areas of mesothelioma. Small tools, inserted through additional incisions, can be used to remove pieces of tissue to examine under a microscope. The specific procedure depends on the area being examined.
Laparoscopy or laparotomy
If there are symptoms in the abdominal area, the doctor may carry out a laparoscopy or laparotomy to examine the area and take tissue samples for testing.
Laparoscopy involves inserting a laparoscope into a small incision in the abdominal wall. The laparoscope has a small camera, like the thoracoscope. Samples can be taken.
If more information is needed, a laparotomy may be requested. The surgeon opens and examines the abdomen. Tissue samples may be removed and sent to the lab.
A pathologist can look at the tissue or fluid samples through a microscope, to see whether there is a malignancy, what types of cells are involved, and how advanced the cancer is.
If the surgeon plans to remove all or part of a lung, lung function tests may be carried out to assess how well the lungs are working, before surgery. This will show whether it is safe to carry out surgery.
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Surgical Biopsy. In some cases, more invasive procedures may be needed to get a large enough tissue sample to make a diagnosis. In that case, a surgeon may perform a thoracotomy (opening the chest cavity) or laparotomy (opening the abdominal cavity) to remove a larger sample of the tumor or the whole tumor.
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Bronchoscopic Biopsy. This procedure involves passing a long, thin, flexible tube down the throat to examine the airways for tumors. If a tumor is found, the doctor can remove a small sample of it through the tube.
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Imaging Tests. These tests allow your doctor to view the inside of your body noninvasively. Imaging tests commonly used in mesothelioma diagnosis include Chest x-ray, Computed Tomography (CT), Positron-emission-tomography (PET), Magnetic resonance imaging (MRI).
Staging of Mesothelioma
Diagnosis will confirm whether cancer is present, and how far it has spread. The stage of cancer will be assigned between stage 1 and stage 4.
Stage 1 mesothelioma the cancer is still localized inside the lining around the lung. It has not spread. At Stage 4, it has spread to distant organs and around the chest.
Treatment of Mesothelioma
Treatment will depend on several factors, including:
- the location of the cancer
- the stage of the cancer
- the patient's general health and age
 Three standard types of treatment are used: surgery, radiation, and chemotherapy. Treating mesothelioma often involves a combination of two or all three. Highly advanced tumors can no longer be surgically removed. The only remaining option in many cases is to try to control cancer, slow it down, and maximize comfort for the patient.
Treatment at a late stage can sometimes cause severe side effects, so pain management and optimizing quality of life may be the better option. The doctor, patient, and family members should discuss the variety of treatment options thoroughly.
Surgery. The four main surgeries used in mesothelioma treatment are:
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Surgery: The surgeon removes the tumors with an invasive procedure. Normally, this is only appropriate during the early stages. Removing all or part of cancer can slow tumor growth and relieve symptoms. Sometimes, the surgeon will remove the lung and surrounding tissue, followed by radiation therapy.
- A pleurectomy or peritonectomy removes the lining around the lungs or abdominal cavity, to relieve symptoms. A tumor that cannot be completely removed may be debulked, or reduced in size. A catheter or tube may be installed to relieve fluid on the lungs.
- Pleurodesis: Drugs such as tetracycline or bleomycin are inserted between to pleura. This inflames the pleura, bringing them back together and blocking potential fluid buildup in the space.
- Wide local excision, which removes cancer along with some of the healthy surrounding tissue.
- Extrapleural pneumonectomy, which involves removing one whole lung and part of the lining of the chest, the diaphragm, and lining of the sac around the heart.
Chemotherapy: If tumors cannot be surgically removed, chemotherapy may be used to shrink them and slow their progress. Chemotherapy is a cancer treatment that uses drugs to stop the growth of mesothelioma cells, either by killing the cells or by stopping them from dividing.
Chemotherapy can be given by mouth, injected into a vein or muscle to enter the bloodstream and reach mesothelioma cells throughout the body, or it can be placed directly into the affected area of the body to mainly affect mesothelioma cells in that area. Sometimes doctors use more than one chemotherapy drug.
This is called combination chemotherapy.
Neoadjuvant chemotherapy may be applied before surgery to make it easier to remove a tumor. Adjuvant chemotherapy is used after surgery to prevent a recurrence.
Radiation therapy: This may be used to reduce the severity of symptoms in those with pleural mesothelioma. It is sometimes used to prevent metastasis after a biopsy or surgery.
Radiation therapy is a type of cancer treatment uses high-energy X-rays and other types of radiation to kill mesothelioma cells or keep them from growing.
Radiation may be administered externally or internally. External radiation therapy uses a machine outside the body to send radiation toward cancer. Internal radiation uses a radioactive substance sealed in needles, seeds, wires, or catheters that are placed directly into the area near the mesothelioma.
Cancer cells may be left behind after surgery and continue to recur. Chemotherapy or radiation therapy can sometimes reduce this risk.
Complications of Mesothelioma
As pleural mesothelioma spreads in the chest, it puts pressure on the structures in that area. This can cause complications, such as:
- Difficulty breathing
- Chest pain
- Difficulty swallowing
- Pain caused by pressure on the nerves and spinal cord
- Accumulation of fluid in the chest (pleural effusion), which can compress the lung nearby and make breathing difficult
Prevention of Mesothelioma
Reducing your exposure to asbestos may lower your risk of mesothelioma.
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References
- Asbestos exposure & the development of mesothelioma cancer. (2017, Jan 11). Retrieved from https://www.mesotheliomahelp.org/asbestos/
- Asbestos-related disease. (2013)
