Mesothelioma Types

If you have been diagnosed with mesothelioma, you may feel overwhelmed by all the medical words you hear in your doctor’s office. To help you understand a mesothelioma diagnosis, it’s useful to start from the ground up and understand mesothelioma types and the terminology that goes with them.

What Is Mesothelioma?

Mesothelioma is a rare cancer caused by exposure to asbestos fibers. The most common place that people with mesothelioma encounter asbestos is at work, but you may have been exposed at home or elsewhere. All of the mesothelioma types can appear many years after asbestos exposure. Mesothelioma diagnosis often happens 40 years or more after the time you came into contact with asbestos.

Mesothelioma affects the mesothelium. The mesothelium is a thin layer of tissue, like a sac, that surrounds and protects various organs in your body, including your lungs and the organs in your abdomen.

Mesothelioma can take the form of a single tumor or multiple tumors. Some mesothelioma types can appear as diffuse, small nodules rather than one larger growth.

Common Mesothelioma Types

We sort these types based on where the mesothelioma tumor is found in the body. There are four mesothelioma types, but up to 95% of mesothelioma cases fall into the two most common types.

Pleural mesothelioma is by far the most common of the mesothelioma types. As many as three quarters of the mesothelioma cases diagnosed each year are pleural mesothelioma.

Mesothelioma is most often caused by invisible asbestos fibers that float through the air. These fibers are inhaled and then lodge in your lung tissue. If your body can’t expel these tiny, sharp invaders, they create irritation that can turn into lung cancer or pleural mesothelioma over time.

Pleural mesothelioma is a cancer of the pleura. The pleura is the lining around the lungs. The pleura has different parts or layers. The visceral pleura clings to the surface of the lungs and forms a protective barrier. The parietal pleura is the next layer. It lines the thoracic cavity or the space inside your ribcage where your lungs and heart are located. You may hear doctors discussing different parts of the parietal pleura: the cervical pleura or cupula of pleura is close to your spine behind your lungs; the costal pleura sticks to your ribcage; the mediastinal pleura covers the center of your chest cavity, surrounding the heart and windpipe as well as lymph nodes.

The space between the different layers of pleura or membranes inside your chest is called the pleural cavity. This space naturally contains fluids. If you develop pleural mesothelioma, you may develop excess fluid in your pleural cavity or lungs, which can lead to some of the uncomfortable symptoms of this most common of the mesothelioma types.

The symptoms of pleural mesothelioma can include:

  • Shortness of breath
  • Coughing up blood or blood in the saliva
  • Chest pain
  • Fluid in the lungs
  • Cough that lingers
  • Wheeziness

These aren’t the only possible symptoms of pleural mesothelioma and any of these conditions may be signs of other ailments. If you have been exposed to asbestos, it’s a good idea to get checked out periodically by an experienced mesothelioma doctor, who is familiar with mesothelioma types and can look for the signs of this cancer.

Peritoneal mesothelioma is the second most common of the mesothelioma types. It affects about 20% of the people who are diagnosed with mesothelioma. The peritoneum is the mesothelium or membrane that surrounds your abdominal cavity and all the organs inside it.

Like the pleura, the peritoneum is made up of multiple layers or parts. The visceral peritoneum is the inner mesothelium, which hugs the organs in your abdomen and protects them. The part of the visceral peritoneum that surrounds your intestines is called the mesentery. The parietal peritoneum is an outer layer that lines the pelvis and abdomen.

As with the mesothelium around your lungs, the space between these layers is a peritoneal cavity that is filled with fluid. Peritoneal mesothelioma can cause an excess of fluid buildup. There are two different peritoneal mesothelioma types, depending on whether there is fluid buildup. The type referred to as dry peritoneal mesothelioma has one large tumor or several smaller tumors and little or no fluid buildup. The wet version of peritoneal mesothelioma type usually involves diffuse cancer cells that don’t form into tumors and are spread across the peritoneum. This version is accompanied by ascites. Ascites is a medial term to describe abnormal fluid buildup in the peritoneal cavity. Ascites can cause bloating and discomfort that lead to some of the symptoms of this mesothelioma type.

The symptoms of peritoneal mesothelioma can include:

  • Unusual loss of weight
  • Pain in the abdominal area
  • Bloating or swelling (caused by excess fluid in the peritoneal cavity)
  • Blockage of the bowels

Peritoneal mesothelioma can be difficult to diagnose. Like pleural mesothelioma, the symptoms can also be indicative of other illnesses. For both of these mesothelioma types, it’s important to let your doctor know that you have a history of asbestos exposure, so you can look for the signs of the various mesothelioma types when searching for a diagnosis.

Rare Mesothelioma Types

There are two more mesothelioma types. Together, they account for less than 5% of the mesothelioma cases diagnosed each year. Because they are so uncommon, it can take some medical sleuthing to discover that your symptoms are caused by one of these mesothelioma types.

Pericardial mesothelioma affects the pericardium, or the lining around your heart. It has some of the same symptoms as pleural mesothelioma, though it can present somewhat differently. Because it’s so rare, the symptoms are not well known.

The pericardium has two layers. The outer membrane is called the fibrous pericardium. It not only encases and protects your heart but also tethers it to the chest wall. The serous pericardium is the membrane that sits closest to the heart. This part of the mesothelium is broken down into two more parts: the parietal pericardium and the visceral pericardium. Both of these layers of pericardium act to create a slippery surface against which the heart can beat without resistance. These two layers cover different parts of your heart, as well as the big veins and arteries that channel blood into and out of it.

The fluid in the pericardium is called serous or pericardial fluid. Like the other mesothelioma types, pericardial mesothelioma can be accompanied by excess pericardial fluid.

The symptoms of pericardial mesothelioma can include:

  • Chest pain
  • Difficulty breathing
  • Fatigue or weakness
  • A condition called pericardial tamponade, where the fluid buildup presses on the heart
  • Pulmonary embolism (blockage of an artery in the lung)

In addition, pericardial mesothelioma can cause a condition known as constricted pericarditis. In this condition, the pericardium becomes thick and stiff, instead of thin and supple. This stiffness impairs heart functioning, because the heart can’t move as freely in the chest cavity.

Like other mesothelioma types, pericardial mesothelioma has symptoms that overlap with other conditions. It can take some trial and error before coming to a mesothelioma diagnosis.

Testicular mesothelioma is the rarest of the mesothelioma types. It affects the mesothelium around the testicles or scrotum.

The mesothelium around the testicles or testes is called the tunica vaginalis. This type of mesothelioma is sometimes called mesothelioma of the tunica vaginalis. The tunica vaginalis has two layers: the visceral lamina and the parietal lamina. The visceral lamina covers most of the testicles and the tube that connects them to the rest of the male reproductive system. This tube is called the epididymis. The parietal lamina is the larger outer membrane, covering more of the epididymis and all of the testes. The cavity of the tunica vaginalis, also referred to as the cavum vaginale, is the space between the visceral and parietal lamina. Also like other mesothelioma types, testicular mesothelioma may be characterized by fluid buildup in this cavity.

The symptoms of testicular mesothelioma may include:

  • Excess fluid in the scrotum (a condition known as hydrocele)
  • Lump in the testicles
  • Swelling or pain in the testes

The only way to confirm a diagnosis of testicular mesothelioma is through a biopsy. Doctors will usually order other tests first, to rule out more common ailments. Your history of asbestos exposure may be the only clue that ultimately leads your medical team to discover testicular mesothelioma.

This is the very rarest of the mesothelioma types; less than one percent of patients have testicular mesothelioma. The good news is that, with treatment, this form may have a better prognosis than other mesothelioma types.

Diagnosing Mesothelioma Types

The methods your doctor will use to diagnose your illness will depend on which of the mesothelioma types you have. A mesothelioma diagnosis is rarely easy. Symptoms of each of the mesothelioma types can be (and often are) mistaken for other illnesses. Because mesothelioma is not a common ailment, even among those who worked or lived around harmful asbestos fibers without proper protection, your doctor will want to rule out other diseases before investigating mesothelioma.

Since all of the mesothelioma types may include excess fluid between the mesothelial layers, the first step is often to drain this fluid. This will relieve the pressure and some of the discomfort for most mesothelioma types, at least temporarily. Your doctor may send some of the fluid to the lab for analysis, but mesothelioma types of cancer are not usually diagnosed this way, because there aren’t enough cancer cells in the fluid.

Patients with pleural mesothelioma are sometimes treated with antibiotics because their symptoms look like pneumonia. Peritoneal mesothelioma can appear to be a hernia or irritable bowel syndrome at first. Pericardial and testicular mesothelioma may present much like other diseases of the heart or testes.

Each of the mesothelioma types can cause the mesothelium to become thick and stiff. This change may show up on tests such as MRIs or CT scans.

When initial treatments don’t work or if scans indicate thickening of the mesothelial tissue, your medical team will need to take a sample of the tissue in the affected area to test in the lab. The only way to determine beyond a doubt that you have one of the mesothelioma types is through laboratory analysis of the cancerous cells.

Fine-needle aspiration is a minimally invasive technique where a needle is inserted into the tumor to retrieve a cell sample. This may not provide enough cells to determine for certain if you have mesothelioma.

A biopsy will remove a larger tissue sample for analysis. There are different types of biopsies. An incisional or core biopsy removes a small sample of cancerous cells from the affected area. Your surgeon may decide to simply remove the whole tumor and analyze it in the lab afterward. This is called an excisional biopsy.

Cancer Staging and Mesothelioma Types

If you have known someone diagnosed with cancer, you have probably heard them refer to cancer stages. Medical professionals usually divide cancer into four stages. At Stage I, the cancer is limited to the original spot of the tumor. Stage IV indicates that the cancer has spread to other parts of the body. This cancer spreading is called metastasis and the cancer is said to have metastasized.

Because mesothelioma is rare, researchers have not developed clear systems for staging all the mesothelioma types. When you receive a mesothelioma diagnosis, your doctor may not be able to tell you what stage the cancer has reached.

Pleural mesothelioma is the best understood of the mesothelioma types and your doctor may be able to stage your pleural mesothelioma. At Stage I, the cancer is limited to its origin in the mesothelium around the lungs. Your treatment options can include surgery, chemotherapy, radiation, and immunotherapy.

In Stage II, the mesothelioma remains limited to just one side or hemisphere of your body, but it has spread to lymph nodes in the chest. The most common places for pleural mesothelioma to metastasize are in the chest, throat, and face. You may still be able to use a wide range of treatment options, including surgery, at stage two.

By Stage III, the cancer has metastasized to other spots in your body, in addition to the lymph nodes. At this point, chemotherapy and radiation are more likely to be helpful rather than surgery.

In Stage IV, the mesothelioma has crossed into the other hemisphere of your body. By this point, mesothelioma treatment is less likely to slow the disease. Patients in stage four of pleural mesothelioma generally focus on things that will make them more comfortable. This type of treatment is called palliative care.

If you believe you may have any of the mesothelioma types described here, seek out medical attention immediately. The sooner you are diagnosed, the better your outcome is likely to be.