Like all cancers, everyone’s mesothelioma diagnosis is a little different. Mesothelioma can attack different parts of the mesothelium, technically defined as single layer of flattened cells forming an epithelium that lines serous cavities including the peritoneum, pleura, and pericardium.
That single fact turns mesothelioma into several distinct diseases rather than just one as each carries with it a different set of symptoms and certainly a different prognosis.
Hence, not all mesothelioma cases and diagnoses are created equal. You may be exposed to the same asbestos that also sickened the gentlemen who worked beside you at the steel mill for 30 years, but he may be diagnosed with one type and you another.
There’s no proven reason why someone gets one particular type of mesothelioma and someone else is diagnosed with another type, researchers say. It’s a veritable crapshoot, so to speak.
Nevertheless, while a few types of the disease are the most common, a victim of asbestos-caused cancer can be diagnosed with any of the four types, each named for the part of the body affected by the disease.
Below is an overview of each the different types of mesothelioma including information that will help you – the patient, or you – the caregiver – better understand the specifics of the disease.
Malignant Pleural Mesothelioma (MPM) is the most common form of the disease. It accounts for approximately 75 percent of all mesothelioma cases diagnosed in the U.S. each year, according to the American Cancer Society.
This type attacks the pleura, which coats the lungs and includes the space in the chest that contains the lungs.
Symptoms of pleural mesothelioma, which often do not surface until the disease has progressed, can be mistaken for a variety of less serious illnesses, like a cold or bronchitis or perhaps even heart problems. These symptoms most often include but are not limited to:
Anyone who worked regularly with asbestos in years past should consult a doctor immediately if any of these symptoms arise without explanation. It is not unusual for there to be a delay in diagnosis of MPM while less serious reasons for the symptoms are researched.
It is ALWAYS important to tell your doctor about your past exposure when such symptoms arise. The earlier the diagnosis, the more options for treatment.
Because malignant pleural mesothelioma is the most-often diagnosed form of the disease, it is also the type of mesothelioma that has garnered the most attention from researchers and doctors searching for better treatments for this type of cancer and, hopefully, a cure someday.
As with all forms of mesothelioma, treatment options will depend on many factors, including the stage of the cancer as well as the age and overall health of the patient. An oncologist may suggest:
Surgery – In some cases up to about Stage 2 (sometimes Stage 3), patients may undergo a pneumonectomy (removal of the diseased lung), pleurectomy (removal of a portion of the lung); or extrapleural pneumonectomy (removal of the diseased lung, the pleura, the pericardium, and part of the diaphragm).
All of these surgeries are serious and carry much risk, so doctors make sure a patient is in otherwise good health before suggesting such procedures. Anyone whose mesothelioma has greatly metastasized will not be a candidate for these forms of surgery.
Chemotherapy – The only chemo drug that’s FDA-approved and specifically recommended for mesothelioma treatment is generally the drug of choice for pleural mesothelioma patients undergoing chemo.
It’s called pemetrexed (brand name: Alima™) and its use is often combined with another chemotherapeutic agent such as cisplatin. It has showed the best results in the treatment of this disease. Other chemo drugs may be used as well if the patient cannot tolerate pemetrexed.
Radiation – In some cases, radiation will be recommended to shrink the tumor and to lessen pain or other discomfort deriving from the symptoms of pleural mesothelioma.
Peritoneal Mesothelioma affects the peritoneum, the lining of the abdomen. It accounts for about 18-20 percent of the 3,000 or so cases of mesothelioma diagnosed each year in the U.S.1, generally fewer than 500 annually.
This type of the disease tends to spread quite quickly through the rest of the body; hence, prognosis for someone with peritoneal mesothelioma is not good. Symptoms of the disease include but are not limited to:
The treatment for peritoneal mesothelioma will vary from that offered for pleural mesothelioma and the options for treating this type of the disease are generally even less successful than those used to treat the pleural type, unfortunately.
Surgery – Only in very rare cases is surgery offered to a patient with peritoneal mesothelioma. That’s because it’s generally diagnosed very late and has already metastasized to the lymph nodes and other parts of the body. In the rare instance that it is suggested, the surgery of choice will probably be a peritonectomy, which removes the cancerous portion of the lining of the abdomen. It may also involve removal of parts of the bowel, liver, pancreas, spleen, gall bladder, and stomach. It may be followed by chemotherapy. When this surgery is used, life expectancy can indeed be extended.
Chemotherapy – The type of chemo used to treat peritoneal mesothelioma is very different from what’s used for the pleural form of the disease. Generally, what is prescribed is known as intraperitoneal chemotherapy, which involves injecting a high concentration of the drug directly into the peritoneal cavity. It is then allowed to sit there for an appointed amount of time in hopes of tackling the tumors. Heated intraperitoneal chemo (HIPEC), however, may also be an option and has shown some success. It is used along with surgery to, hopefully, prolong life and reduce pain. For this type of treatment, however, the cancer must NOT have spread beyond the abdomen.
Radiation – Because the peritoneum wraps around organs such as the stomach, liver, and intestines, all of which could be affected by radiation therapy, it is only recommended in very rare cases.
Pericardial Mesothelioma, which develops in the lining around the heart, is a much rarer type of the disease, accounting for only about one percent of all annually-diagnosed U.S. cases. It carries with it a very high mortality rate, with victims surviving only a short time after diagnosis.
Pericardial mesothelioma is often mistaken for other diseases including coronary heart disease, heart failure, tuberculosis pericarditis, cardiac tamponade, and cardiomyopathy.
If you are experiencing the above symptoms and have worked with asbestos in the past, it is ESSENTIAL to inform your doctor as to the specifics of your exposure so he may rule out or confirm pericardial mesothelioma.
Because the disease indirectly involves the heart, traditional cancer treatments such as surgery, chemotherapy and radiation are usually not even considered, though they could be helpful in very rare cases.
Surgery – A pericardiectomy removes all or part of the lining of the heart. It can relieve pressure and minimize fluid build-up. It is rarely used because it is truly only viable in the diseases very early stages. Sometimes, instead, a pericardiocentesis can be used to remove fluid via a fine needle and catheter.
Palliative therapies – A palliative therapy is one which seeks to reduce the pain of cancer and to minimize other symptoms of the disease. The only options that fall into this category for pericardial cancer patients is the aforementioned pericardiocentesis and appropriate oral or intravenous pain meds.
The rarest of all forms of the disease, Testicular Mesothelioma develops in the lining of the testicles, known as the tunica vaginalis. Patients with this disease will probably notice swelling of the scrotum and lumps in the area of the testicles. (The rarity of the disease has made it difficult to compile a complete symptom list.) Studies note that fewer than 100 cases have been diagnosed thus far.
Histology, or the study of cells and cell types, can figure greatly into how a particular type of cancer is treated, including mesothelioma.
Specifically, mesothelioma histology – the study of cells from someone with mesothelioma – is known as histopathology, because it involves “diseased” cells. Histopathology is the realm of the pathologist, a doctor who examines tissue samples (biopsies) from diseased individuals to obtain an accurate diagnosis.
The pathologist’s work will play into the overall plan for treatment though the patient will likely never see him or her.
Nevertheless, the type of cellular structure of one’s mesothelioma remains an important part of the equation and, as mentioned, will impact the effectiveness of treatment options as well as overall life expectancy.
In addition, histopathology will also help doctors avoid misdiagnosis, especially when it comes to two types of cancer that are difficult to differentiate.
For example, some types of lung cancer and mesothelioma are not easily distinguishable from one another.
There are three cell types associated with a mesothelioma diagnosis. They are:
Epithelial cells – Epithelial cells appear in the tumors of about 50-70 percent of all mesothelioma patients, making them the most common cell type. These cells are structured in an orderly fashion and are sharply defined, which makes them easier to identify. Tumors diagnosed as epithelial respond best to treatments, which can indicate a better prognosis and longer life expectancy for the patient.
Sarcomatoid cells – These cells are identified by their spindle shape and are found in approximately 10 to 20 percent of mesothelioma tumors. They are indeed among the more aggressive cell types and, hence, do not respond well to treatment. Thankfully, however, they are far less common than the epithelial type. Sarcomatoid tumors are generally not eligible for resection.
Biphasic cells – This type of cellular structure has characteristics of both epithelial mesothelioma and sarcomatoid mesothelioma. About 20 to 35 percent of all cases present biphasic cells. A tumor can only be dubbed biphasic if each type accounts for a minimum of 10 percent of the mass of the tumor. The biphasic cell type is also less responsive to treatment than a tumor made up of just epithelial cells.