Mesothelioma is an often fatal form of cancer that develops in the lining (or mesothelium) of various organs. But, mesothelioma is not a uniform disease, and, as such, it is categorized into several different types and subtypes.
The most common way to distinguish between different types of mesothelioma is the location of the disease. It can also be further distinguished by cell type and tumor type.
The different kinds of mesothelioma often determine how a patient is treated and what their prognosis will be. All forms of mesothelioma are caused by exposure to asbestos, but that doesn’t mean they aren’t different.
We’ll discuss more about these different types below.
Again, the most common method for distinguishing mesothelioma types is by location.
Mesothelioma occurs in four different locations throughout the body.
The four location types are:
- Pleural (occurring in the lining of the lungs)
- Peritoneal (occurring in the lining of the abdomen)
- Pericardial (occurring in the lining of the heart)
- Testicular (occurring in the lining of the testes)
Again, each location type requires a different treatment regimen and different overall care. Let’s take a look at each of them individually.
Pleural mesothelioma is the most common type of the disease accounting for between 70 and 90% of all cases. It affects the pleura, or the lining of the lungs. Individuals who incur this form of the disease were exposed to asbestos at high levels for prolonged periods of time. Because of this prolonged exposure, they likely inhaled the fibers. Asbestos then lodged itself into the lining of their lungs.
Over time, the caustic asbestos fibers begin to irritate the lining, causing inflammation and, eventually, pleural effusion (fluid buildup in the lungs). Like most other types of mesothelioma, the pleural variety takes many years (on average, between 30 and 40) to begin producing symptoms and most cases aren’t caught until the later stages of the disease.
Symptoms for the pleural form of the disease are generally localized to the chest area. These include:
- Shortness of breath (dyspnea)
- Pain in the chest
- Trouble speaking because of hoarseness
- Problems with swallowing (dysphagia)
- Pleural effusion
- Pain in the lower back
As time passes, these symptoms gradually get worse and the individual usually seeks out medical attention. Pleural mesothelioma is diagnosed through the use of various tests. First, a doctor will likely call for imaging scans, like an X-ray, MRI, CT-Scan, or PET scan.
These scans will allow the doctor to identify if there is anything abnormal growing in the chest cavity near the lungs. Blood tests and biomarker tests may also be ordered to see if the patient’s blood gives any indication of something wrong.
The only method for definitively diagnosing pleural mesothelioma is with biopsies. A needle biopsy (in this case, a thoracentesis) can draw fluid from the pleura to identify whether the cells are malignant. For a truly definitive diagnosis, a surgical biopsy, which is more invasive and removes a chunk of the affected lung tissue, is necessary.
Pleural mesothelioma is notoriously hard to diagnose because of its similarity to other, more prevalent diseases.
Early on, a doctor may think it’s any of the following:
- Chronic pulmonary obstructive disorder (COPD)
Even after a biopsy is performed, the pleural form of the disease sometimes gets misdiagnosed as another type of lung cancer, like adenocarcinoma. If mesothelioma is determined to be present, the doctor will likely begin a treatment regimen for the patient. If the disease is caught in the initial stages, curative treatments may be prescribed to fight the spread of the disease.
The most prominent curative treatment is surgery. Surgical procedures for pleural mesothelioma include:
- Pneumonectomy (removal of a lung)
- Extrapleural pneumonectomy or EPP (removal of a lung and portions of the chest lining, heart lining, lymph nodes, and diaphragm)
- Pleurectomy / Decortication (removal of the lining of the lung and nearby tumors while keeping the lung itself intact)
Surgeries typically improve patient prognosis, particularly when chemotherapy and radiation therapy are also involved. If, however, the patient is diagnosed with late stage pleural mesothelioma, then major surgeries may not be an option. In stages 3 and 4 (the last two stages), the disease has typically metastasized and spread to other regions of the body, making surgery inadvisable.
In this case, doctors may prescribe palliative treatments that improve the patient’s quality of life. One such treatment, pleurodesis, removes fluid buildup from the pleura and then seals the pleura so leakage isn’t possible in the future. This helps with symptoms like shortness of breath and chest pain.
Survival rates, the measures of how long patients survive after diagnosis, for the pleural type of the disease range depending on the amount of time.
For pleural mesothelioma survival rates are:
- 1 year: 73%
- 3 years: 23%
- 5 years: 12%
- 10 years: less than 5%
This means, if you have 100 patients, you can expect 73 of them to survive one year after diagnosis, but fewer than 5 are expected to be alive ten years after diagnosis. Survival rates are obviously better for patients whose disease was caught early and who received aggressive treatment.
Peritoneal mesothelioma is the second-most generic form the disease, accounting for 10 to 30% of all cases. It forms in the lining of the abdominal cavity, although it is somewhat unclear how asbestos travels to the abdomen. Prominent theories suggest that asbestos arrives at the abdomen through simple ingestion or by being transported through the lymphatic system.
Again, symptoms of all kinds of mesothelioma often take decades to start appearing.
Symptoms for the peritoneal variety include:
- Swelling in the abdomen due to fluid buildup (known as ascites)
- Severe abdominal pain
- Loss of appetite
- Weight loss
- Bowel obstruction
As with the pleural form of the disease, peritoneal mesothelioma is diagnosed with a range of tests like imaging scans, blood tests, and biopsies. The only difference, of course, is that the focus will be on the abdomen.
Peritoneal mesothelioma can also be mistaken for other diseases including:
- Irritable bowel syndrome
- Other cancers of the abdomen
- Ovarian cancer
- Crohn’s disease
Once a diagnosis is accurately made, doctors will begin a treatment regimen. Again, treatment typically involves a combination of surgery, radiation therapy, and chemotherapy. The two surgeries in this case are the peritonectomy, which removes a portion of the peritoneal cavity, and cytoreductive surgery, which attempts to eliminate or weaken tumors and cancerous cells in the abdomen. Some surgeries may take portions of abdominal organs like the pancreas or liver.
A new therapy used for peritoneal mesothelioma has shown great effectiveness in recent years. The hyperthermic (or heated) intraperitoneal chemotherapy (HIPEC) has been shown to increase survival rates by 50%. HIPEC is an intraoperative chemotherapy, meaning that it is administered during cytoreductive surgery. It involves heating up a selection of drugs and injecting them directly onto tumors for short periods of time.
Because of HIPEC, survival rates have improved dramatically in recent years:
- 1 year: 92%
- 3 years: 74%
- 5 years: 65%
- 10 years: 39%
Again, catching the disease early and engaging in high-quality treatments always help with the prognosis.
Pericardial mesothelioma is odd not just because of its rarity. It only accounts for about 1% of all mesothelioma cases, meaning that it’s not very well-understood. In fact, one study that looked at 103 patients showed that only 25% of them had ever been exposed to asbestos on a large scale.
This has led researchers to speculate that pericardial mesothelioma is actually just one of the two more common forms of the disease that has metastasized and attacked the lining of the heart.
In any event, the pericardial variety of the disease is more difficult to accurately diagnose because of its exceeding rarity. It can also appear as many other cancers and diseases like angiosarcoma, adenosarcinoma, lymphoma, carcinoma, heart disease, and numerous others.
Symptoms can include:
- Chest pain
- Heart murmurs
- Excess fluid around the pericardium (lining of the heart)
- Inflammation around the heart
- Low blood pressure
- Trouble breathing
- Irregular heartbeat
Again, a lot of these symptoms overlap with symptoms of other diseases, making pericardial mesothelioma very difficult to detect. Even so, imaging scans, blood tests, and biopsies are again the go-to for doctors trying to make a diagnosis. Once diagnosed, doctors will start a treatment regimen.
Surgical options include:
- Pericardiectomy (removal of the lining of the heart)
- Pericardiocentesis (removal of fluid buildup around the heart)
- Percutaneous balloon pericardiotomy or PBP (a different method for removing fluid buildup)
A pericardiectomy is only a viable option when the disease is caught in the early stages and the patient is healthy enough to undergo major surgery. Pericardiocentesis and PBP are often used as palliative treatments to alleviate pain. Chemotherapy and radiation therapy can also be applied, although radiation therapy has not shown much efficacy for this type of mesothelioma.
Pericardial mesothelioma has one of the worst prognoses. Most patients who are diagnosed with the disease have a life expectancy of only 5 months. In many cases, the incidence of pericardial mesothelioma goes undetected until after death.
Testicular mesothelioma is even rarer than the pericardial type with only 100 reported cases throughout the world. As the name suggests, this mesothelioma type affects the testes, although its relationship to asbestos exposure isn’t well-understood, either.
Like pericardial mesothelioma, testicular mesothelioma is thought to be a more common form of the disease that simply metastasized.
Despite this, there are symptoms unique to this form of the disease:
- Groin pain
- Testes pain
- Fluid buildup that causes swelling in the scrotum
- Cysts in the epididymis
- Lump on the testicles
For this type of the disease, doctors can use an ultrasound to provide an image of the interior of the scrotum. There are also many biomarkers that can be identified via blood tests, including:
- Cytokeratin 5/6
- Wilms’ tumor gene 1
- Epithelial membrane antigen
Because data on this form of the disease is scarce, there really is no agreed-upon treatment method. Naturally, chemotherapy, radiation therapy, and surgery can be used, but there is no consensus on what works best.
Surgery does have the best outcomes largely because tumors are often localized to one testicle. A scrotal orchiectomy, which removes one or both testicles, may be performed by a surgeon. The inguinal orchiectomy is the same as the scrotal orchiectomy except that it removes the spermatic cord in addition to one or two testicles. Patients who undergo an inguinal orchiectomy have recurrence rate of 25% less than those who undergo a scrotal orchiectomy.
The life expectancy for testicular mesothelioma is usually between 1 and 2 years, but many individuals have survived longer than that.
In addition to the location of the disease, the mesothelioma cell type can also play a role in treatment plans and overall prognoses. The disease’s cell type is usually determined after sample tissue from a biopsy has been examined.
There are three main types of cells when it comes to mesothelioma. These include:
Epithelioid cells are the most common, making up about 50 to 70% of all mesothelioma diagnoses. They can appear in peritoneal and testicular forms of the disease, but they are much more commonly found in the pleura. The prognosis is generally better for epithelioid cells than it is for any other cell type. Life expectancy ranges from 18 to 24 months.
Sarcomatoid cells, by contrast, are usually the most aggressive. They account for roughly 10 to 20% of all cases, and are more commonly found in the peritoneal form of the disease than any other. Because of the rapidly spreading nature of sarcomatoid cells, life expectancy is extremely poor and most patients only receive palliative care. For peritoneal sarcomatoid mesothelioma, life expectancy is generally less than 5 months. It’s not much better for pleural mesothelioma where life expectancy with sarcomatoid cells is only 8 months.
Biphasic cells are a mix of the two main cell types. Biphasic mesothelioma can be found in virtually every form of the disease but is most common in peritoneal mesothelioma. The prognosis for this cell type variety differs depending on which cell type is more dominant. If epithelioid cells are dominant, the disease will be easier to treat. Of course, the reverse is true if sarcomatoid cells are dominant. Overall life expectancy is between 10 and 15 months.
Treatment really depends on the location type of the disease. Again, a combination of surgery, chemotherapy, and radiation therapy produces the best results. If sarcomatoid cells are present, the most common form treatment is palliative as most major surgeries would only cause the patient more pain and discomfort.
The tumor type typically refers to malignancy. Most mesothelioma tumors are malignant, meaning that they can spread to other areas of the body and will require treatment. Pleural, peritoneal, pericardial, and testicular types of the disease almost always have malignant mesothelioma tumors.
Benign mesothelioma tumors are incredibly rare, with only 200 known cases having been reported. Benign mesothelioma tumors can become malignant if they are allowed to remain in the body. They can be surgically removed with relatively low rates of recurrence.