What Are the Different Types of Mesothelioma?
Mesothelioma is a rare form of cancer that affects the mesothelium, the thin membrane of epithelial cells that lines the lungs, abdomen and heart. There are three types of mesothelioma that can develop from exposure to asbestos fibers. The type of mesothelioma depends primarily on the location of the tumors in the body. It can also be further categorized according to the type — or types — of cancer cells present.
Pleural mesothelioma affects the lining of the lungs and chest cavity, or the pleura. Pleural mesothelioma is caused by asbestos inhalation. After breathing in asbestos dust, the asbestos fibers lodge in the lining of the lungs and chest. Over time, the fibers irritate the pleural lining, causing scar tissue and inflammation. Eventually, the cells can mutate and form malignant tumors.
Pleural mesothelioma is the most prevalent type of mesothelioma; between 70 and 90 percent of patients are diagnosed with this type of mesothelioma. Although the prognosis depends on the stage and cell type, the average life expectancy for pleural mesothelioma patients is between 8 and 21 months.
Symptoms of pleural mesothelioma include:
- Chest pain (35–71% of patients)
- Fatigue (18–33% of patients)
- Fever (6–33% of patients)
- Persistent dry cough (6–37% of patients)
- Shortness of breath (35–82% of patients)
- Weight loss (9–59% of patients)
The majority (54–87 percent) of pleural mesothelioma patients also experience a buildup of fluid around the lungs (called pleural effusion), which can make breathing difficult and painful.
Because the symptoms mirror those of other respiratory illnesses — such as the flu, COPD, and pneumonia — as well as other types of cancer, the process to diagnose pleural mesothelioma is often a lengthy one. Diagnosis for mesothelioma typically includes imaging tests, blood tests, and biopsies. For pleural mesothelioma specifically, doctors may perform needle biopsies, such as a pleural biopsy or thoracentesis; camera-assisted biopsies, such as a thoracoscopy or mediastinoscopy; or a surgical biopsy called a thoracotomy when other biopsies fail to provide definitive results.
Treatment options for pleural mesothelioma depend on the stage but generally involve a combination of treatments — referred to as a multimodal treatment plan — including:
The two primary surgical options for pleural mesothelioma are pleurectomy with decortication, in which the linings of the lung and chest are removed, along with any visible tumors; and extrapleural pneumonectomy, in which the entire affected lung, the pleural linings of the chest and heart, and portions of the diaphragm are removed. Other surgical procedures such as pleurodesis and thoracentesis may be used to remove fluid that has built up around the lungs to make breathing easier and less painful.
Patients often undergo chemotherapy after surgery in order to destroy any remaining cancer cells; the most common chemotherapy treatment for pleural mesothelioma is a combination of ALIMTA® and cisplatin. Chemotherapy may also be used in lieu of surgery as an aggressive, potentially curative treatment or as a palliative treatment to improve quality of life for late-stage patients.
Radiation may be used before, during, or after surgery to shrink and reduce the spread of tumors in pleural mesothelioma patients. It has also been shown to be effective on its own as a palliative treatment to mitigate the symptoms of pleural mesothelioma by reducing chest pain and easing breathing difficulties.
Immunotherapy drugs are becoming increasingly common in the treatment of pleural mesothelioma. Immunotherapy harnesses the body’s own immune system to attack malignant cancer cells.
Peritoneal mesothelioma affects the lining of the abdomen, or the peritoneum. Peritoneal mesothelioma is caused by asbestos ingestion. After swallowing asbestos dust (either through the mouth or after inhaling it into the sinuses), the asbestos fibers become lodged in the lining of the abdomen. Once there, the fibers irritate the peritoneum, causing inflammation and scar tissue. In time, the cells of this scar tissue mutate and create malignant tumors in the abdominal cavity.
Peritoneal mesothelioma is the second most prevalent type of mesothelioma; between 10 and 30 percent of patients are diagnosed with this type of mesothelioma. The prognosis for peritoneal is better than that of other types of mesothelioma. Although the survival rate depends on the stage and cell type, the average life expectancy for peritoneal mesothelioma patients is between 34 and 92 months.
Symptoms of peritoneal mesothelioma include:
- Abdominal distension (30–80% of patients)
- Abdominal pain (27–69% of patients)
- Diarrhea (17% of patients)
- Fatigue (11–43% of patients)
- Fever (22% of patients)
- Hernia (7–12% of patients)
- Nausea or vomiting (11–15% of patients)
- Weight loss (32–38% of patients)
Many patients (36–90 percent) also experience a buildup of fluid in the abdomen (called ascites), which can cause additional pain and bloating.
Because the symptoms mirror those of other abdominal illnesses — such as IBS — as well as stomach or ovarian cancer, diagnosing peritoneal mesothelioma can take weeks or even months. As with pleural mesothelioma, diagnosis for peritoneal mesothelioma usually includes imaging tests, blood tests, and biopsies. For peritoneal mesothelioma specifically, doctors may perform needle biopsies, such as a paracentesis; camera-assisted biopsies, such as a laparoscopy (also called a peritoneoscopy); and a surgical biopsy called a laparotomy when other, less invasive biopsies fail to provide definitive results.
A multimodal approach is recommended for the treatment of peritoneal mesothelioma. The specific treatment plan will depend on the stage, but like treatment for pleural mesothelioma typically includes surgery, chemotherapy, radiation, and immunotherapy.
The main treatment for peritoneal mesothelioma is a combination of cytoreductive surgery, in which the surgeon attempts to remove all visible peritoneal tumors from within the abdominal cavity; and Hyperthermic Intraperitoneal Chemotherapy (HIPEC), a heated chemotherapy wash that is applied to the abdominal cavity immediately following surgery in order to kill any cancer cells that may remain. Radiation may be used before or after surgery to reduce tumor size and prevent the cancer recurring.
As with pleural mesothelioma, chemotherapy and radiation can also be used as palliative treatment options to mitigate symptoms in late-stage patients for whom cytoreductive surgery and HIPEC are not options. Likewise, paracentesis may be used to remove fluid that has built up in the abdomen to reduce abdominal pain and swelling.
Pericardial mesothelioma affects the lining of the heart, or the pericardium. Because it is the rarest form of mesothelioma, affecting less than 5 percent of mesothelioma patients, the exact causes of pericardial mesothelioma are still unclear, but doctors suspect that asbestos fibers enter the body through inhalation or ingestion, then reach the heart via the bloodstream or lymphatic system. At that point they become embedded in the heart lining, creating scar tissue and, eventually, tumors along the lining of the heart sac.
Unfortunately, most cases of pericardial mesothelioma are only discovered at an advanced stage (usually by accident during surgery) or after death. Because of this, the prognosis for pericardial mesothelioma is poor; the average life expectancy for pericardial mesothelioma patients is under one year.
Symptoms of pericardial mesothelioma include:
- Chest pain
- Heart murmur
- Weight loss
Patients may also experience a buildup of fluid around the heart (called pericardial effusion), which can cause increased chest pain and make breathing difficult and painful.
Because the symptoms mirror those of other cardiac illnesses — such as heart disease or inflammation of the heart muscle — it is difficult to diagnosis pericardial mesothelioma. Diagnosis for mesothelioma typically includes imaging tests, blood tests, and biopsies. For pericardial mesothelioma specifically, doctors may perform an echocardiogram, which uses sound waves to assess heart function; and pericardiocentesis, a type of needle biopsy.
As with other forms of mesothelioma, the treatment options for pericardial mesothelioma depend on the stage at which the patient is diagnosed. If curative treatment is an option, it will usually involve a pericardiectomy, a surgery that involves the removal of some or all of the pericardium, as well as chemotherapy with cisplatin. Palliative treatments for pericardial mesothelioma include pericardiocentesis (also called a pericardial tap) and percutaneous balloon pericardiotomy, both of which can help relieve pericardial effusion around the heart. During pericardiocentesis, a doctor uses a needle and catheter to remove fluid from the pericardium. Percutaneous balloon pericardiotomy is similar to pericardiocentesis, but the catheter has an inflatable balloon at the end, which the doctor repeatedly inflates to create a small hole in the pericardium, allowing them to drain more of the effusion. Chemotherapy may also be used to slow the spread of tumors in later-stage patients to mitigate symptoms such as chest pain or difficulty breathing.