Malignant mesothelioma, a rare form of cancer, can affect different parts of the mesothelium in a person’s body. When a person develops signs or symptoms of malignant mesothelioma, it can be extremely important to know the area where the mesothelioma has occurred, as well as the distinct type of classification of the cancer so that the patient’s doctors and treatment team can determine the patient’s options for treatment. The location and type of mesothelioma can affect how well certain types of treatments can work, and they can also indicate in some circumstances how the patient’s mesothelioma may have resulted from a particular form of asbestos exposure. Some types of mesothelioma are much more common than others.
The most common form of mesothelium is pleural mesothelioma, which affects the pleura of the patient, and the most common type or classification is epithelioid mesothelioma. As such, a majority of mesothelioma patients are diagnosed with epithelioid mesothelioma of the pleura. The Mayo Clinic, the American Lung Association, and the American Cancer Society provide extensive information about the types of malignant mesothelioma and the ways in which these cancers are diagnosed and treated.
Specific Kinds of Mesothelioma based on the Cancer Location
It is important to know that there are different kinds of mesothelioma, and that the different kinds of this cancer are determined by which part of the mesothelium in a person’s body has been affected. Depending upon where in the body the mesothelium is located, it will have different names. Those names do not include the word “mesothelium,” so it is important to understand that all of the following are the mesothelium in different areas of a person’s body:
- Pleura, which is mesothelium or lining that covers a person’s lungs and the space within their chest where the lungs are located;
- Peritoneum, which is mesothelium or lining in a person’s abdomen, as well as the lining for many of the organs that are located in a person’s abdomen;
- Pericardium, which is mesothelium or lining of the heart, as well as the space inside a person’s chest that contains the heart; and
- Tunica vaginalis, which is mesothelium or lining of a person’s testicles.
Where mesothelium exists, malignant mesothelioma can occur. The four types of malignant mesothelioma include the following:
- Pleural mesothelioma;
- Peritoneal mesothelioma;
- Pericardial mesothelioma; and
- Tunica vaginalis mesothelioma.
Classifications of the Different Types of Mesothelioma
When a healthcare provider believes you have mesothelioma, they will take a biopsy that will be sent to a laboratory for further assessment. At the laboratory, a pathologist will review the biopsy and will classify the cancer according to the way the cancer cells look. Within these classifications based on the location of the tumor, malignant melanomas are further classified into one of three categories based on the characteristics of the cancer cells. Those categories include the following:
- Epithelioid: Approximately 50 percent of diagnosed malignant mesotheliomas fall into this category, and these types of cancer have the best prognosis. Epithelioid mesothelioma cancer cells resemble adenocarcinoma cells, which are found in lung cancer. When a pathologist examines the cells in a biopsy and those cells look like the epithelial type of mesothelioma, the pathologist will apply a specific type of stain to the biopsy to determine whether you have mesothelioma or lung cancer or adenocarcinoma. Epithelial cells are those that line both internal and external body parts. When a pathologist is looking at a biopsy, that pathologist also can use the term “epithelial” to describe the type of mesothelioma cells on the sample.
- Sarcomatoid, or fibrous: Approximately 7 to 20 percent of malignant mesothelioma cases fall into this category. This is a more aggressive type of mesothelioma than epithelioid mesothelioma. This is the least common type of mesothelioma, and the cells look quite different from epithelioid mesothelioma. Typically, sarcomatoid mesothelioma cells have a spindly appearance, and they may resemble supportive tissue or connective tissue in the human body.
- Mixed, or biphasic: Approximately 20 to 30 percent of diagnosed malignant mesotheliomas have areas that are classified as both epithelioid and sarcomatoid. This type of mesothelioma can be described either as biphasic or mixed. When a pathologist examines the cells from a biopsy under a microscope, the cancer cells have the appearance of both epithelial cells and of sarcomatoid mesothelioma cells. This type of mesothelioma is less common than epithelioid mesothelioma, but it is more common than sarcomatoid mesothelioma alone.
How the Different Types of Malignant Mesothelioma are Determined
As explained above, a biopsy is necessary to definitively diagnose malignant mesothelioma and to determine the area of the cancer cells and their specific type. Before a biopsy occurs, a patient will typically visit a healthcare provider with symptoms associated with one of the forms of mesothelioma. The patient’s doctor will usually perform a physical exam and will look for signs of mesothelioma that appear without scans or invasive assessments. For example, some types of mesothelioma will produce lumps under the skin, or may appear as a mass or tumor. The doctor will also ask the patient about any risk factors, such as exposure to asbestos through work or in the home, or a family history of mesothelioma.
After a physical exam, a healthcare provider will usually order a scan to get a better look at the area of the patient’s body where the mesothelioma may exist. The most common types of scans used in the process of diagnosing different types of malignant mesothelioma include X-rays and computerized tomography (CT) scans.
Depending upon the results from a physical exam and any X-rays or CT scans, your healthcare provider next may order a biopsy. When you have a biopsy performed, you should know that this means your healthcare provider will be removing a small sample of tissue or fluid in order to send it to a laboratory in order to have it assessed for indications of malignant mesothelioma. A biopsy is the only definitive way to determine whether you have mesothelioma, and to determine what type of cancer cells exist in your body. Once the biopsy results come back, your doctor may order subsequent tests to determine whether the mesothelioma has spread, and then can discuss potential treatment options with you.
Biopsies are used to identify most types of cancer in the human body, and all biopsies involve the removal of either cells or tissue from a person’s body so that they can be assessed under a microscope at a laboratory by a pathologist. There are different types of biopsies that can be performed based upon the reason for the biopsy and the amount of the sample that is necessary to diagnose mesothelioma or another type of cancer. If a sample of a patient’s cells or tissue is removed from the body, this is known as an incisional biopsy, or sometimes described as a core biopsy. This type of biopsy can occur when a needle is inserted into the patient’s body and a fluid or cell sample is removed, or during a surgical procedure in which a sample of cells or tissue gets removed. A biopsy done with a needle is often described as a needle biopsy or as a fine-needle biopsy. If a tumor or entire area of the patient’s body is removed for biopsy, that biopsy is known as an excisional biopsy. In most mesothelioma cases, a biopsy of the patient’s pleura is necessary to make a mesothelioma diagnosis.
What is a pathologist? A pathologist is a type of doctor who is responsible for assessing the cells contained in the biopsy. According to Johns Hopkins Medicine, a pathologist’s primary responsibilities include examining body tissues and performing laboratory tests. Pathologists are important in diagnosing any type of cancer or other disease in which cells must be examined closely to make a diagnosis, and the work of pathologists is important for ultimately determining the treatment options that are available to a patient who has been diagnosed with mesothelioma?
Risk Factors for Different Types of Mesothelioma to Tell a Doctor
There are many different possible risk factors for malignant mesothelioma. What is a risk factor? As the American Cancer Society explains, a “risk factor is anything that increases your chance of getting a disease such as cancer,” and “different cancers have different risk factors.” There are some types of risk factors that a person can control, such as behaviors or life choices. Then there are other risk factors for certain cancers over which a person has no control, such as genes and genetics, or age. It is important to understand that having a risk factor does not necessarily mean that you will develop cancer. Further, it is important to know that some people who develop malignant mesothelioma do not have any risk factors, while many people with one or more risk factors do not develop malignant mesothelioma.
- Exposure to asbestos, which can occur as a result of the type of work a person is doing, or living with a person who is exposed to asbestos and brings the fibers home on skin or clothing (common jobs in which asbestos exposure occurs can include, for example, construction workers, industrial and manufacturing workers, shipyard workers, plumbers, electricians, home renovators, miners, and firefighters);
- Exposure to zeolites, which are also minerals that occur naturally (like asbestos) but are found more often in certain parts of the country including Arizona, Montana, Nevada, Oregon, South Dakota, and Utah;
- Radiation exposure, including radiation as treatment for certain types of cancer;
- Infection with Simian Virus 40 (SV40), which is most often linked to contaminated vaccines such as those used to prevent polio in the late 1950s and early 1960s;
- Older age, since cancer is more likely to occur in older people, and most cases of mesothelioma caused by asbestos exposure do not occur for 20-50 years from the initial exposure;
- Being male, given that there are significantly higher incidence rates among men, yet researchers suggest that the gender divide in mesothelioma diagnosis is likely due to the types of jobs that men are likely to do and where asbestos exposure is most likely to occur; and
- Having a genetic predisposition to mesothelioma, which can mean that you have a family member who was diagnosed with mesothelioma or you have a particular genetic mutation (to the BAP1 gene) that increases your risk of developing mesothelioma.
In some cases, asbestos exposure does not result in malignant mesothelioma but can be responsible for asbestosis or lung cancer. When asbestos is coughed up and swallowed, the fibers can enter the person’s abdomen and can cause mesothelioma of the peritoneum. Given that asbestos is linked to so many cases of mesothelioma, it is especially important to inform your doctor of any possible asbestos exposure at work, in the home, or otherwise.
Symptoms of the Different Types of Malignant Mesothelioma
The symptoms of malignant mesothelioma can vary depending upon where in the body the cancer occurs. It is also important to know that different people can experience varying symptoms of mesothelioma, and some rarer types of mesothelioma have symptoms that may not be obvious. If you or someone you love has any of the risk factors for mesothelioma, especially known exposure to asbestos, it is important to see a healthcare provider in order to receive an accurate diagnosis. The Mayo Clinic identifies some of the most common symptoms of each type of mesothelioma, and any of these signs should necessitate a visit to your doctor’s office.
Pleural mesothelioma often has one or more of the following signs and symptoms:
- Chest pain
- Coughing that is painful
- Shortness of breath
- Lumps under the skin on your chest
- Weight loss that is unexplained
Peritoneal mesothelioma commonly has one or more of the following signs and symptoms:
- Pain in the abdomen
- Swelling in the abdomen
- Weight loss that is unexplained
Pericardial mesothelioma often will have one or more of the following signs and symptoms:
- Difficulty breathing
- Chest pain
Tunica vaginalis mesothelioma will often have one of the following signs:
- Swelling of the testicle(s) or
- Mass on a testicle
When mesothelioma starts to spread, it can cause additional signs and symptoms. With spreading pleural mesothelioma in particular, a person may experience increased difficulty breathing and increased chest pain, and that person may also experience problems swallowing, nerve pain, spinal cord pain, and pleural effusion. Pleural effusion is a term that refers to the accumulation of fluid in a person’s chest, which can result in lung compression and can make it more difficult for the person to breathe.
As the Mayo Clinic underscores, many of these signs and symptoms are also associated with other diseases and conditions. Accordingly, you should not necessarily assume that one of the above signs or symptoms is a clear indicator of malignant mesothelioma. However, these signs and symptoms should be evaluated by a healthcare provider. Further, since mesothelioma symptoms can also be signs of many other types of conditions or diseases, it is important to receive a medical assessment. Malignant mesothelioma is quite rare, and many other conditions that have some of the same or similar signs and symptoms occur much more frequently than mesothelioma.
Why is it Important to Diagnose the Specific Type of Mesothelioma?
Diagnosing the specific type of mesothelioma in a patient is essential to determining what possible treatment options may look like for that patient. When a pathologist provides information about the biopsy, that information can help the patient’s doctors to determine important information about the type of cancer cells and, in some cases, the extent of the spread of the mesothelioma. By knowing what type of mesothelioma cells the patient has and where the mesothelioma is located, the patient’s doctors can come up with treatment options that may be effective to reduce the spread of the cancer, to make the patient more comfortable, and to limit symptoms. While a patient’s specific treatment will depend upon the type of mesothelioma, the location of the cancer, and the extent of the spread of the disease, common treatment options can include the following:
- Surgery, which can include removal of areas that show mesothelioma and can, in some cases, involve removal of an entire organ such as a lung
- Chemotherapy, which is treatment that kills cancer cells
- Radiation, which focuses energy beams on a specific area of the body where mesothelioma exists;
- Immunotherapy, which is a type of treatment that gives the patient’s immune system a chance to fight back against the cancer and
- Targeted therapy, which involves the use of particular drugs that target the type of mesothelioma
In many cases, more than one type of treatment may be used, and treatment options can be combined with one another. For example, surgery and chemotherapy may be used in conjunction with one another, or surgery and radiation may be used together. Unfortunately, most mesothelioma cases are caught at a stage that is too advanced for the cancer to be cured, but one or more of the above treatments may extend a patient’s life or may help a patient to avoid suffering from some of the symptoms associated with mesothelioma. Researchers continue to look at targeted therapies based on mesothelin, which is a particular protein that is located on the outside portion of epithelioid mesothelioma cells. In addition, researchers continue to explore ways in which surgical procedures can be employed to treat mesothelioma based on the particular type and characteristics of the disease.