The mesothelium is a membrane that covers and protects most of the internal organs. It is made up of 2 layers. The inner layer envelops various organs, including the lungs, heart and stomach. The outer layer forms a bag that surrounds the inner layer. There is a little liquid between the 2 layers, which facilitates the movement of the organs.
The mesothelium has different names depending on where in the body it is located. The mesothelium that forms a protective cushion around the lungs is called the pleura. The inner layer, which covers the lungs, is called the visceral pleura. The outer layer, which lines the inner wall of the chest, is called the parietal pleura.
The mesothelium that covers the abdominal organs and that lines the walls of the abdomen and pelvis is called the peritoneum. The inner layer, which envelops and supports most of the internal abdominal organs, is called the visceral peritoneum. The outer layer, which lines the walls of the abdomen and pelvis, is called the parietal peritoneum.
The mesothelium is made up of mesothelial cells. These cells sometimes undergo changes that make their growth pattern or behavior abnormal. These changes can lead to the formation of non-cancerous (benign) tumors, such as the fibrous tumor of the pleura and multicystic mesothelioma. However, in some cases, changes in mesothelial cells can cause malignant mesothelioma.
Mesothelioma is a very rare type of cancer. It usually appears in the pleura. In this case, it is called pleural mesothelioma. This type of cancer accounts for 70 to 80% of all cases of mesothelioma. Mesothelioma can also arise in the peritoneum; it is then called peritoneal mesothelioma. This type of cancer accounts for about 25% of all cases of mesothelioma.
Rare types of mesothelioma can also occur. One of them is pericardial mesothelioma, which occurs in the membrane surrounding the heart (pericardium). Another rare type is mesothelioma of the vaginal lining, which appears in the outer lining of the testes.
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Mesothelioma is a cancerous tumor of the mesothelium that can invade and destroy nearby tissue. It can also spread (metastasize) to other parts of the body. The mesothelium is the coating that lines the outer surface of most internal organs. Depending on the organ it covers, it can have different names.
Pleural mesotheliomaPleural mesothelioma starts in the pleura, the membrane that covers the lungs. It is the most common type of mesothelioma. More men than women are diagnosed with pleural mesothelioma.
Peritoneal mesotheliomaPeritoneal mesothelioma begins in the peritoneum, which lines the inside of the abdomen and covers many abdominal organs. It is the second most common type of mesothelioma. It occurs in both men and women.
Rare mesotheliomasThe following cancerous mesothelium tumors are very rare.
The pericardial mesothelioma starts in the pericardium, the casing that surrounds the heart. The most common symptoms of pericardial mesothelioma are heart problems caused by the tumor or an accumulation of fluid around the heart. These include chest pain, chest pain that gets worse when you breathe deeply or cough, breathing problems, anxiety, or restlessness. Another symptom of this type of cancer is palpitations (a feeling that the heart is beating hard, very quickly, or irregularly). Treatment may include surgery, radiation therapy or chemotherapy. Pericardial mesothelioma is associated with a very poor prognosis (expected outcome).
The mesothelioma of the tunica vaginalis originates in the tunica vaginalis, the casing that covers the testicles. Its most common symptoms are pain and swelling of the testicles. It is treated with surgery during which the testicles, scrotum and lymph nodes present in this region are removed. Radiation therapy may be offered after surgery. As this disease is very rare, the role of chemotherapy in the treatment of mesothelioma of the vaginal coat remains unknown.
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Cell types of mesotheliomaMesothelioma can also be described according to the cell structure of the tumor, which is determined by examining samples under a microscope. Mesothelioma can be of 3 main cell types.
Epithelioid mesothelioma is the most common cell type. It has a more favorable prognosis than other cell types.
The second most common cell type is sarcomatoid , or fibrous, mesothelioma . It spreads faster than epithelioid mesothelioma.
Mixed, or biphasic, mesothelioma is made up of tumors that contain both epithelioid and sarcomatoid regions. Tumors that contain more epithelioid cells have a better prognosis than those that contain more sarcomatoid cells.
Benign mesotheliomaNon-cancerous, or benign, mesothelioma is a mass that appears in the mesothelium and does not spread to other parts of the body (no metastasis). Tumors of benign mesothelioma are not usually life threatening. Usually, they are removed by surgery and they do not reappear (no recurrence). There are a few types of benign mesothelioma.
Fibrous tumor of the pleuraThis tumor can arise in the thin tissue that covers the lungs (visceral pleura), or in the tissue that lines the chest cavity and that surrounds the lungs (parietal pleura). Many of the symptoms caused by fibrous tumors of the pleura are the same as those of malignant mesothelioma, such as shortness of breath.
This type of tumor can reappear after surgery. In some cases, a localized fibrous tumor of the pleura is actually cancerous.
Multicystic mesotheliomaMulticystic mesothelioma forms many benign cysts in the thin covering that lines the inside of the abdomen (called the peritoneum). This type of mesothelioma occurs more often in women. It is sometimes also called benign cystic mesothelioma.
Adenomatoid mesotheliomaThis type of benign mesothelioma can arise in the mesothelium that covers the reproductive organs. In women, it can form in the fallopian tubes. In men, it can appear in the epididymal ducts, which carry sperm out of the testicles.
Prognosis and survival for mesotheliomaIf you have mesothelioma, you may have questions about your prognosis. Prognosis is the act by which the doctor best assesses how cancer will affect a person and how he will react to treatment. Prognosis and survival depend on many factors. Only a doctor who knows your medical history, the type, stage and characteristics of the cancer you have, the treatments chosen and the reaction to treatment can review all of this data in conjunction with survival statistics to arrive at a prognosis.
A prognostic factor is an aspect of cancer or a characteristic of the person that the doctor considers when making a prognosis. The following are prognostic factors for mesothelioma.
Cell subtypeThe cell subtype is an important prognostic factor for mesothelioma. Epithelioid mesothelioma is the most common subtype of mesothelioma and has a better prognosis than the sarcomatoid or mixed types. Mixed tumors that contain more epithelioid cells have a better prognosis than those that contain more sarcomatoid cells. The sarcomatoid subtype produces the least favorable prognosis regardless of the treatment administered.
StadiumThe stadium plays a role in the prognosis of people who are going to have surgery. In general, the prognosis for people with stage 1 or 2 mesothelioma is better than that for people with stage 3 mesothelioma.
The prognosis for mesothelioma that has spread to the lymph nodes (stage 3 or 4) is less favorable.
Surgical removal and surgical marginsIf one can completely remove the mesothelioma by surgery, the prognosis is more favorable than if one cannot remove it entirely.
A negative surgical margin means that there are no cancer cells in the edges of the tissue that was removed during surgery, while a positive surgical margin means that it has been detected. In the presence of positive margins, the risk of recurrence is higher and the prognosis is less favorable than in the presence of negative margins.
Chest painThe prognosis for someone diagnosed with pleural mesothelioma with chest pain is bleak, as it may indicate that the cancer is so advanced that it cannot be removed by surgery.
Functional indexThe functional index is used to assess how well a person is able to perform everyday tasks and daily activities. The prognosis for a person with a low functional index is less favorable than that for a person with a good or acceptable functional index.
WeightlossThe prognosis for a person who has lost a lot of weight before being diagnosed is less favorable than that for a person who has lost little.
AgePeople over the age of 60 who are diagnosed with mesothelioma survive less than those who are diagnosed with it at a younger age.
SexMen who are diagnosed with mesothelioma have a poorer prognosis than women who have it.
Increased number of platelets and white blood cellsThe prognosis for a person with mesothelioma whose platelet count is higher than normal (thrombocytosis) is less favorable than that of a person whose platelet count is normal.
In addition, the prognosis for a person with a high white blood cell count (hyperleukocytosis) is less favorable than that for a person with a normal white blood cell count.
Above normal lacticodehydrogenase (LDH) levelLacticodehydrogenase (LDH) is an enzyme found in almost every cell in the body. When cells are damaged or destroyed, they release LDH into the blood. A higher than normal LDH level therefore means that cells or tissues are damaged somewhere in the body.
The prognosis for a person with mesothelioma whose LDH level is higher than normal is less favorable than that of a person whose LDH level is normal or low.
Treatments for mesotheliomaIf you have mesothelioma, your healthcare team will develop a treatment plan specifically for you. This plan will be based on your health and cancer-specific information. When your healthcare team decides which treatments to offer you for mesothelioma, they take into consideration the following:
- where mesothelioma originated
- the mesothelioma subtype
- if mesothelioma can be removed by surgery
- your overall health
- your personal preferences
- You may be offered one or more of the following treatments for mesothelioma.
SurgeryIf you are healthy enough to have an operation, you may be offered surgery to treat a mesothelioma that can be removed.
Pleural mesotheliomaThe following types of surgery are used to treat pleural mesothelioma.
During an extrapleural pneumonectomy , the parietal and visceral pleura are removed, the lung on the side where the mesothelioma originated, part of the diaphragm and the lymph nodes of the thorax. You may also want to remove the envelope that surrounds the heart (called the pericardium).
During a pleurectomy / decortication , the parietal and visceral pleura and the tumor are removed, but the lung is not removed.
The palliative surgeries designed to relieve symptoms such as pain or difficulty breathing.
- When shrinking, as much of the mesothelioma is removed as possible, but the portion removed is smaller than in the case of pleurectomy / decortication.
- During thoracentesis, the fluid that surrounds the lungs is removed.
- During pleurodesis, the parietal pleura and the visceral pleura are sealed together to prevent fluid buildup between them.
Peritoneal mesotheliomaIn general, it is not possible to operate on people with peritoneal mesothelioma because this cancer has usually spread too much to be able to completely remove it. Surgery is often used to relieve symptoms caused by peritoneal mesothelioma. The following types of surgery can be offered.
During tumor reduction , all or as much of the mesothelioma is removed as possible. We remove the lining of the abdomen (peritoneum) and the layer of fatty tissue that covers the organs of the abdomen (omentum). Other tissues and organs may need to be removed, such as part of the intestines, the gallbladder, or the appendix.
During a paracentesis , the fluid that has accumulated in the abdomen (ascites) is removed. A hollow needle or tube (catheter) is used to remove fluid from the abdominal cavity.
ChemotherapyMost people with mesothelioma receive chemotherapy.
Pleural mesotheliomaIn the presence of pleural mesothelioma, chemotherapy is used after surgery; if surgery cannot be performed, it can also be used as the main treatment.
The most common chemotherapy combinations used to treat pleural mesothelioma are:
- cisplatin and pemetrexed (Alimta)
- cisplatin and raltitrexed (Tomudex)
- pemetrexed and carboplatin (Paraplatin, Paraplatin AQ) - may be offered to people with other health conditions who cannot receive cisplatin
- cisplatin and gemcitabine (Gemzar)
- vinorelbine (Navelbine)
Peritoneal mesotheliomaIn the presence of peritoneal mesothelioma, chemotherapy constitutes a regional treatment, that is to say that it is administered directly into the peritoneal cavity. This is called intraperitoneal chemotherapy.
The most common chemotherapeutic agents used as intraperitoneal chemotherapy to treat peritoneal mesothelioma are:
- mitomycin (Mutamycin)
- doxorubicin (Adriamycin)
- External radiation therapy is used to treat mesothelioma.
Pleural mesotheliomaAfter extrapleural pneumonectomy, radiation therapy can be given to the side of the chest from which a lung has been removed. Radiation therapy is not offered after pleurectomy / decortication, as it may damage the lung.
Radiation therapy can also be used to relieve symptoms caused by pleural mesothelioma, such as coughing or shortness of breath.
Peritoneal mesotheliomaRadiation therapy is not used as the primary treatment for peritoneal mesothelioma because the organs in the abdomen are sensitive to radiation. It can be used to relieve pain and other symptoms caused by advanced peritoneal mesothelioma.
If you cannot or do not want cancer treatmentYou may want to consider care that makes you feel better without treating the cancer itself, perhaps because cancer treatments are no longer working, or are more likely to improve your condition, or their side effects are difficult to tolerate. There are other reasons why you cannot or do not want cancer treatment.
Talk to members of your healthcare team. They can help you choose the care and treatment for advanced cancer .