Occupational Hygiene Blog

What is Mesothelioma?

Updated: Apr 13, 2021

Mesothelioma is a rare form of cancer that typically develops in the tissue lining (mesothelium) of the lungs or abdomen. In rare cases, tumours can also grow in the linings of the heart or testicles.

Mesothelioma takes anywhere from 20-50 years to develop in the body. However, once it begins to spread (metastasize), it does so quickly. There is no cure for mesothelioma, but medical treatments may extend or improve a patient’s life.

Quick Facts About Mesothelioma

The only known cause of mesothelioma is inhaling or ingesting asbestos fibres. Mesothelioma can only be treated effectively by specialists located at cancer centres around the country. The average life expectancy for someone with mesothelioma is 12-21 months. Aggressive treatments like surgery, chemotherapy, and radiation may help slow disease progression and extend a patient’s life expectancy. Mesothelioma is often misdiagnosed because it shares symptoms with other, more common diseases.

Types of Mesothelioma

There are four types of mesothelioma. Each type occurs in a different location in the body. The type of mesothelioma that a patient has helps determine what kind of treatment they receive.

Here are the four types of mesothelioma:

1. Pleural Mesothelioma

Pleural mesothelioma affects the protective lining that covers the chest cavity and lungs (pleura). It is the most common type of the disease, accounting for 80-90% of all cases.

2. Peritoneal Mesothelioma

Peritoneal mesothelioma develops in the lining of the abdomen (peritoneum). It is the second most common form of the disease, affecting 10-20% of all patients.

3. Pericardial Mesothelioma

Pericardial tumours form in the pericardium, the lining surrounding the heart. Pericardial mesothelioma accounts for less than 1% of all cases.

4. Testicular Mesothelioma

Testicular mesothelioma develops in the lining of the testicles (tunica vaginalis). Testicular mesothelioma is extremely rare, and less than 300 cases have been reported.

Mesothelioma Cell Types

Mesothelioma tumours are made up of cancerous cells. However, there are a few different types of mesothelioma cells. Which cells are present will help doctors determine the best treatment plan, as some cell types respond better to treatment than others.

The most common mesothelioma cell types are: 


This is the most common mesothelioma cell type. Epithelioid cells typically lump together to form tumours. Compared to the other cell types, epithelioid cells divide at a slower rate, making it easier for doctors to treat.


Sarcomatoid cells grow at a faster rate than epithelioid cells. These cells do not appear as frequently as epithelioid cells and may be mistaken for other types of cancer.

For these reasons, it is harder for doctors to treat this cell type.


Some mesothelioma tumours contain both epithelioid and sarcomatoid cells. When both cells are present, the tumour is said to be biphasic. To treat a biphasic tumour, doctors will study the tumour to see which type of cell is more common. If more epithelioid cells are present, the tumour will be easier to treat because the tumours will not develop as quickly.

Mesothelioma Causes

Asbestos exposure is the only known cause of mesothelioma. Asbestos is a natural mineral composed of tiny, tinsel-like fibres. These fibres are fine, durable shards that can withstand high levels of heat, chemical or water exposure when bound together. Asbestos fibres are also extremely flexible, allowing them to be used in a variety of products.

From the 1920s until the 1980s, asbestos was widely used in blue-collar industries and the military. As early as the 1930s, claims of asbestos-related health risks came to the surface but were ignored. Manufacturers were warned of the risks that people faced when using asbestos or asbestos-containing products. One serious risk was increased evidence of a link to cancer. However, they hid the truth since they knew they could make a huge wartime profit in World War II. Their selfishness has led to thousands of preventable deaths.

How Asbestos Exposure Leads to Mesothelioma

Asbestos fibres are released into the air when disturbed and settle on nearby surfaces. These microscopic fibres can be breathed in or swallowed by unsuspecting victims.

Once inside a person’s body, the fibres can embed themselves deep into the tissue lining of various organs.

How asbestos exposure causes mesothelioma:

A product or piece of equipment with asbestos is handled. The asbestos fibres in these products are disturbed and released into the air. Nearby workers and other individuals inhale or ingest the airborne fibres. The fibres become stuck inside the tissue linings of a person’s body. Over time, these fibres cause cancerous mesothelioma tumours to grow.

Rapid tumour growth damages the affected organs, preventing them from functioning properly. If the spread of cancer is not stopped, it will become fatal.

Who is at Risk for Mesothelioma?

Anyone who has come in contact with asbestos may be at risk for mesothelioma. Even a single asbestos fibre may cause cancerous tumours to develop. However, some people are at a greater risk than others.

Those with a higher risk of mesothelioma include:


Many jobs — particularly industrial and blue-collar ones — put workers in direct contact with asbestos. Since asbestos had many useful properties, a wide assortment of industries relied on it.

High-risk occupations for asbestos exposure include: 

Construction Workers, Firefighters, Insulators, Mechanics, Shipbuilders. Many of these occupations exposed workers to asbestos on a daily basis. Because of this, they are more likely to develop mesothelioma decades after the fact.


Veterans are at a higher risk of mesothelioma because asbestos was widely used by the military. From the 1930s to the 1980s, the military relied on asbestos products to make its ships, bases, and vehicles resistant to enemy fire. In the process, thousands of military service members were exposed to asbestos. The military did not know asbestos was dangerous because the companies who made and sold asbestos products concealed the truth.

Today, 1 out of every 3 people diagnosed with mesothelioma is a veteran.

The following military branches used asbestos: 

Air Force, Army, Coast Guard, Marine Corps, Navy -

Navy veterans have the highest risk of mesothelioma because asbestos products were used extensively throughout many Navy ships.

Family Members and Loved Ones

The family and loved ones of industrial workers and veterans are also at risk of mesothelioma. While they didn’t directly handle asbestos products, they may have suffered second-hand exposure. When asbestos products are disturbed they enter the surrounding air and can get stuck to nearby surfaces without notice. This includes uniforms, hair, and tools used by workers. Workers could then bring asbestos into their home without realising it. For example, there have been reports of wives developing mesothelioma after decades of washing their husbands’ clothes. They had been regularly washing asbestos-laced clothing for years without knowing the deadly health risks.

Mesothelioma Symptoms

As with most cancers, mesothelioma symptoms differ for each person based on factors like age, sex, and overall health level.

Common symptoms of mesothelioma include:

Cough, difficulty breathing, fatigue, fever, fluid build-up, loss of appetite, night sweats, pain in the affected area - recognising the symptoms and receiving a correct diagnosis early on can greatly increase the odds of long-term survival.

Pleural Mesothelioma Symptoms

Since pleural mesothelioma forms in the lining of the lungs, its symptoms often affect the respiratory system.

Common pleural mesothelioma symptoms include:

Tightness in the chest

Difficulty swallowing

Weight loss

In the early stages of pleural mesothelioma, mild symptoms may be mistaken for other ailments. These symptoms can resemble the flu, chronic obstructive pulmonary disease (COPD) or even the common cold. As the cancer progresses, tumours cause the lining of the lungs to thicken, restricting the lungs from expanding fully. This can prevent a patient from being able to take a deep breath.

Peritoneal Mesothelioma Symptoms

Unlike pleural mesothelioma, there is no official staging system for peritoneal mesothelioma.

Common peritoneal mesothelioma symptoms include:

Abdominal bloating




These common symptoms start off mildly, but as the lining of the abdomen thickens, tumours develop and symptoms become more noticeable. Because of their similarity to other abdominal illnesses, doctors can find it difficult to diagnose these symptoms accurately. Some patients with peritoneal mesothelioma have been misdiagnosed with other conditions such as a ventral hernia, irritable bowel syndrome (IBS) or ovarian cancer.

Pericardial Mesothelioma Symptoms

Pericardial mesothelioma is extremely rare and, as a result, there is not a complete list of symptoms.

Common pericardial mesothelioma symptoms include:

Heart palpitations (arrhythmia)

Heart murmurs

Irregular heartbeat

Symptoms will worsen over time as the lining of the heart thickens and tumours develop. This causes further inflammation and strain on the heart. Because these symptoms are broad, patients may be misdiagnosed with other heart issues.

Testicular Mesothelioma Symptoms

Like pericardial mesothelioma, little is known about testicular mesothelioma. However, there are common symptoms including the inflammation or thickening of the testicular lining. Swelling of the testicles may also be present. Doctors may misdiagnose this form of mesothelioma as a groin hernia or similar condition.

Mesothelioma Diagnosis

Getting an accurate diagnosis from a mesothelioma specialist is essential to receiving effective treatment. Armed with an accurate diagnosis, these doctors can rule out other diseases and develop treatment plans that may extend a patient’s life.

Doctors usually take multiple steps to diagnose mesothelioma in their patients.

Patient Examination and Review of Medical History

Patients who have symptoms of mesothelioma can undergo a physical examination. Doctors will examine the patient’s symptoms, noting how long they have been present.

Patients should tell their doctor about any history of asbestos exposure. If the doctor is concerned, they will often request an imaging scan of the patient’s body as the next step.

Perform Imaging Scans (MRI/CT Scan/X-Ray)

Imaging scans, including X-rays, CT scans and MRIs, allow a physician to determine whether there is a tumour growing in the patient’s body. Doctors often require several scans to rule out of illnesses. For imaging scans like MRIs and CT scans, your doctor can often tell you the results the next day.

While these scans are valuable, mesothelioma cannot be diagnosed by an imaging scan alone.

The final step in diagnosing mesothelioma is to conduct a biopsy.

Conduct a Biopsy

If imaging scans reveal an existing tumour or questionable mass, doctors will order a biopsy. A surgical biopsy removes a tissue sample from a tumour. This sample is studied under a microscope to detect if cancer cells are present. In some cases, patients are unable to undergo a surgical biopsy, and a needle biopsy is performed to examine fluid from the body.

The most accurate type of biopsy is a surgical biopsy and will confirm to doctors whether a patient has mesothelioma. It can take anywhere from 2-10 days for a patient to get the results of a biopsy. Because doctors need to rule out other conditions, they require several scans to confirm a diagnosis. For imaging scans like MRIs and CT scans, your doctor can often tell you the results the next day. It can take anywhere from 2-10 days for a patient to get the results of a biopsy.

Getting a Second Opinion

Because mesothelioma is a rare cancer, it is often misdiagnosed by inexperienced doctors. Receiving a second opinion can also lead to an improved treatment plan. No patient or their family should ever feel embarrassed to seek a second opinion.

Mesothelioma Stages

As part of a diagnosis, doctors will determine how far the cancer has spread throughout the body. In many cases, this is done through a staging system.

There are four stages of pleural mesothelioma, with stage 1 being the least advanced and stage 4 being the most. A patient’s overall outlook is typically worse in the later stages of the disease. Only pleural mesothelioma is broken up into official stages, as there is not enough data for doctors to break the other types into stages. In these cases, doctors will simply say the cancer is local or advanced.

Stage 1

In stage 1, mesothelioma tumours are typically contained to one side of the pleura. The cancer has not spread out to other sites. Patients diagnosed in stage 1 have almost all treatment options — including surgery, chemotherapy, and radiation — available to them.

Stage 2

In stage 2, the cancer has begun to spread to other areas in the body, such as the lungs and chest wall. However, it is still mostly contained to where it started. Patients can greatly benefit from treatments such as surgery in this stage.

Stage 3

By stage 3, mesothelioma tumours can be found throughout the body, such as the heart lining and lymph nodes. In most cases, patients can no longer undergo surgery safely by this point. However, they still may be able to receive treatment through chemotherapy and radiation.

Stage 4

By stage 4, the cancer has spread to distant organs like the liver and brain. Patients diagnosed in this stage typically have limited treatment options, but palliative care can help reduce painful symptoms.

Mesothelioma Prognosis

A prognosis is an overall outlook for the disease. It affects a patient’s treatment options and life expectancy. Because mesothelioma is often diagnosed in the later stages, most patients receive a poor prognosis. Only a handful of mesothelioma patients will ever achieve long-term survival. However, many different factors impact prognosis. These factors vary with each patient.