Mesothelioma Types: Pleural, Peritoneal & Epithelial
There are three primary types of mesothelioma which are defined according to the area of the body where the disease originates.
Mesothelioma is a cancer that affects the mesothelium, a thin protective tissue that lines major organs including the lungs, stomach and heart. Pleural mesothelioma originates in the pleura of the lungs, peritoneal mesothelioma originates in the peritoneum of the abdomen and pericardial mesothelioma originates in the pericardium around the heart.
The onset of mesothelioma is usually very slow. The disease is characterized by a long latency period meaning that it can sometimes take decades for symptoms to develop after someone has been exposed to asbestos. By the time that symptoms begin to develop the disease may have already progressed to advanced stages.
Pleural mesothelioma originates in the chest area and most commonly in the pleura of the lungs. It can also originate in the lining of the chest cavity and diaphragm. Mesothelioma is a very aggressive disease and has the ability to metastasize quickly to other organs.
The most common presenting symptom is persistent pain localized in the chest. Sometimes the pain is accompanied by severe difficulty breathing, due to an accumulation of fluid in the pleural space known as pleural effusion. Cough, weight loss, fatigue and fever are also not uncommon. There are a number of medical tests available to diagnose pleural mesothelioma and measure how far the disease has progressed. These include positron emission tomography (PET scan), MRI, computed chest tomograph (CT-scan) and X-rays.
There are currently no serum markers available for the diagnosis of mesothelioma. The detection of elevated serum levels of hyaluronic acid may be useful in differentiating mesotheliomas from other tumors, or to follow the effect of treatment. The median survival is about 17 months from the beginning of symptoms. The 3-year survival rate for pleural mesothelioma is 10% and the 5-year survival is approximately 5%. Thus, if 100 patients are diagnosed with mesothelioma at a specific point in time, 10 patients will still be alive at the end of 3 years and 5 patients will be alive at the end of 5 years.
Peritoneal mesothelioma is a rare form of asbestos cancer that occurs in the thin membrane which surrounds the abdominal cavity, known as the peritoneum. This thin cell wall acts a lubricant within the abdominal cavity so that nearby organs, such as the liver, spleen and bowel as well as internal body structures may contract and expand normally.
Pain is a common complaint in peritoneal mesothelioma patients. Ascites (fluid accumulation in the abdominal cavity) also causes the abdomen to appear enlarged. As a result, patients can experience nausea, vomiting, swelling of their feet, fever and difficulty moving their bowels. The median survival time for those diagnosed with peritoneal mesothelioma is about 10 months from the onset of symptoms.
Pericardial mesothelioma originates in the pericardium. It is the rarest form of mesothelioma and comprises only 10 percent of all cases diagnosed each year. The symptoms of pericardial mesothelioma are chest pain, difficulty breathing, fatigue and fluid buildup around the heart (pleural effusion).
Echocardiogram and computed tomography diagnostic tests can detect the presence of pleural effusion, a thickened pericardium, and any masses that may be present. The prognosis for pericardial mesothelioma is very poor. This cancer is often not diagnosed until it has reached advanced stages. If the disease is localized, surgery may be recommended. For the most part, however, palliative care is provided to reduce the severity of symptoms and provide comfort to the patient.
Other Types of Mesothelioma
Papillary Mesothelioma - Mesothelioma of the ovaries has also been reported in the literature. The management of this disease differs based on the stage at which it has been diagnosed. The prognosis, however, is very poor.
Testicular Mesothelioma - There are also documented cases of mesothelioma of the scrotum in the literature. Treatment will differ based on the stage of the disease but the prognosis is poor.
Mesothelioma Cell Types
Sarcomatoid Mesothelioma - Sarcomatoid Mesothelioma accounts for approximately 10 to 15 percent of all mesothelioma diagnoses. Although it is the least common histologic subtype it is also the most aggressive type. The cell structures characteristic of this form of mesothelioma are elongated and spindle-shaped, and are typically not arranged in an organized pattern. The sarcomatoid cell structure also lacks a nucleus, unlike epithelioid cells, which have clearly visible nuclei. Traditional biopsy methods pose unique challenges when it comes to diagnosing sarcomatoid mesothelioma. This is because the tests frequently provide false information due to sarcomatoid cells having a similar appearance to benign fibrous tissue. Additionally, histological methods of diagnosis often make it difficult to distinguish between sarcomatoid mesothelioma and other types of unrelated sarcomatoid cancers.
Biphasic Mesothelioma - This type of mesothelioma is characterized by a mix of epithelioid and sarcomatoid cells. About ten to fifteen percent of mesothelioma cases are diagnosed with this cell subtype. It is a more rare form of the disease but also carries a less favorable prognosis than epithelial mesothelioma.
Epithelial Mesothelioma - This histologic subtype is found in approximately sixty to seventy percent of mesothelioma cases. It is the most common variation of mesothelioma and carries the most favorable prognosis of the different types of mesothelioma.
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