What Is Malignant Mesothelioma?

Overview

Malignant mesothelioma is a relatively rare condition that many people have not encountered before. Whether you know a little or a lot, you are in the right place to find out more. 

Our chest wall, abdominal cavity, heart and testes all have a protective lining called the mesothelium. Malignant mesothelioma is a rare form of cancer affecting the cells that make up this protective lining.¹  

In this article, we will discuss the different types of malignant mesothelioma and how they are diagnosed and treated. We will also discuss who is more likely to develop the condition and what you should do if you are worried you might have symptoms. 

Types of malignant mesothelioma 

Pleural mesothelioma

Pleural mesothelioma is a condition that affects the tissue that lines our chest cavity and covers our lungs. According to Cancer Research UK, pleural mesothelioma accounts for over 90% of malignant mesothelioma cases in the UK. 

Peritoneal mesothelioma 

Peritoneal mesothelioma affects the tissue that lines our abdominal wall, known as the peritoneum. The peritoneum also covers many of our abdominal organs. 

Testicular mesothelioma 

Testicular mesothelioma affects the lining of the testicles. 

Pericardial mesothelioma 

Pericardial mesothelioma affects the pericardium, a sheath which lines the heart. 

Risk factors for malignant mesothelioma

Asbestos exposure

The major risk factor for malignant mesothelioma is asbestos exposure.² Asbestos is a material found in a range of products due to its strength, durability, and resistance to heat and electricity. There is typically a time lag between exposure to asbestos and the development of mesothelioma, which can be 40 years or longer.³ Amongst people who have had a high level of exposure to asbestos, there is a 10-25% chance of developing mesothelioma later in life.⁴ 

People assigned male at birth (AMAB) are more likely to develop malignant mesothelioma. This is because people with AMAB were traditionally more likely to be exposed to asbestos at work. High-risk occupations include mining, construction and shipbuilding.⁵

Rates of malignant mesothelioma vary around the world. They are highest in countries where the use of asbestos-containing materials was previously widespread, like in Europe, Australia and New Zealand. The lowest rates are found in parts of Africa and the Middle East, including Pakistan, Bangladesh and Sudan.⁵ 

Due to its carcinogenic properties, asbestos is now banned in many countries.² 

Genetics

Genetics are thought to play a role in some cases. Ionising radiation (e.g. via exposure to radiation therapy) is also thought to increase risk.²

Common signs and symptoms of malignant mesothelioma

Typical symptoms of malignant mesothelioma depend on which part of the body is affected. Many of the signs and symptoms listed below are common in a wide range of conditions and do not necessarily indicate malignant mesothelioma. If you are concerned, approach your healthcare provider for advice. 

Pleural mesothelioma

Some common signs and symptoms are:⁶

• Fluid in the lining of the lungs (pleural effusion) 
• Breathlessness
• Dry cough
• Chest pain
• Tiredness
• Fever and/or sweating, particularly at night
• Unintentional weight loss
• Swollen fingertips

Peritoneal mesothelioma 

Peritoneal mesothelioma may present with:⁷

• Abdominal pain
• Abdominal swelling
• The presence of new lumps or bumps in the abdomen
• Feeling sick 
• Unintentional weight loss
• Changes in bowel habits, such as diarrhoea or constipation

Testicular mesothelioma

Some people with testicular mesothelioma may not have any symptoms. Others may report:⁸ 

• Swelling of the scrotum
• A build-up of fluid around the testicle
• New lumps or bumps on the scrotum 

Pericardial mesothelioma 

Some people with pericardial mesothelioma may not have any symptoms. Others may have:⁹

• A build-up of fluid around the heart (called a pericardial effusion)
• Inflammation of the lining of the heart (called pericarditis)
• Chest pain
• Breathlessness
• Abnormal rhythms of the heart (arrhythmia)
• Cough
• Swelling of the face, feet and/or lower legs 
• Weight loss

Diagnosis of malignant mesothelioma

Pleural mesothelioma

If your doctor thinks that you could have malignant mesothelioma, you may undergo some of the following tests:⁶

1. Imaging: A chest X-ray can help inform your doctor on whether a more detailed CT scan or MRI scan is needed. These scans can pick up abnormalities of the pleura.
2. If you are found to have fluid around your lung(s), taking a sample to examine for cancer cells is often helpful. This procedure is called pleural aspiration (or thoracentesis). 
3. If the cause of your symptoms is still uncertain, your healthcare provider may look directly into the space around your lungs using a camera. This is called thoracoscopy.
4. It can be very helpful to take tissue samples (also known as a biopsy) of any areas of the pleura that appear suspicious on imaging or thoracoscopy to look for cancer cells. Samples may be taken during thoracoscopy itself or during a separate procedure. 

Peritoneal mesothelioma

A CT scan is commonly recommended to those presenting with symptoms of possible peritoneal mesothelioma. It is usually necessary to take a biopsy of any areas where the disease is suspected.⁷ 

Testicular mesothelioma

Testicular mesothelioma accounts for less than 1% of all mesothelioma cases.⁸ Thus, there has been comparatively less research on what diagnostic tests work best. Most people are diagnosed incidentally during an unrelated surgery,⁸ when biopsies are taken.

If you present with symptoms that may suggest testicular mesothelioma, you may undergo some imaging tests to explore the underlying cause. If you are noted to have fluid around your testicle, an ultrasound scan may be carried out.⁸

Pericardial mesothelioma

Pericardial mesothelioma accounts for less than 1% of all malignant mesothelioma cases,⁹ and is difficult to diagnose. This is partly due to a  relative lack of scientific research into the diagnosis of the condition. 

Chest X-rays and Echocardiography (or ECHO) are often used initially to examine the heart and surrounding structures. CT and MRI scanning may be used to look more closely at any suspicious findings detected during earlier tests. If fluid has collected around the heart (called a pericardial effusion), it may be possible to take a sample to examine for cancer cells. 

Histopathology (examination of biopsy samples)

When a tissue sample is taken, it can be reviewed in a laboratory to look for tumour cells and understand more about what they look like. Malignant mesothelioma tumours can be divided into three main subgroups:⁶

• Epithelioid tumours
• Sarcomatoid tumours
• Biphasic tumours (with a mixture of features of both epithelioid and sarcomatoid tumours). 

The type of tumour a person has helps determine what treatment is likely to be helpful. 

Stages of malignant mesothelioma

Cancer staging allows doctors to describe how advanced a person’s cancer is. The TNM system is a commonly used system that reviews what is known about the primary (original) tumour (T), spread to lymph nodes (N) and spread to distant parts of the body (M). Each component is assigned a score and the information is combined to determine the stage of the cancer. Usually, cancers are staged between I and IV, with an increasing number indicating a more advanced cancer.¹⁰

The TNM system is used to stage pleural mesothelioma.¹⁰

A modified version of the TNM staging system may be used to stage peritoneal mesothelioma.11 The Peritoneal Cancer Index (PCI) is an alternative system that splits the abdomen into 13 sections, and each section receives a number between 0 and 3. The higher the number, the more significantly that area is affected. By adding all the numbers together, the stage of peritoneal mesothelioma can be identified.¹²

There is currently no accepted staging system for testicular or pericardial mesothelioma.¹³

Management and treatment for malignant mesothelioma

Treatment of malignant mesothelioma will depend on the type and stage of the cancer, how well the patient is, and their personal wishes.⁶ 

Unfortunately, many cases of malignant mesothelioma are already advanced when they are diagnosed. If it is not possible to cure the disease, you are likely to be offered palliative treatment. Palliative treatment aims to improve symptoms, quality, and sometimes length of life.⁶ 

Pleural mesothelioma

Surgical options: Some people may be offered surgery to remove all or part of their pleural mesothelioma. Unfortunately, this rarely cures the disease because it is difficult to remove all the cancer cells. If you have symptoms like breathlessness arising due to an accumulation of fluid on the lung (pleural effusion), you may be offered a procedure to drain the fluid and fix the layers of the pleura together to prevent it from reaccumulating (pleurodesis).⁶ 

Non-surgical options: People with malignant mesothelioma are often offered chemotherapy.⁶ Chemotherapy is a medicine that can kill cancer cells and is usually given into a vein through a drip. Less often, radiation therapy may be offered, which uses high-energy rays to kill cancer cells.⁶

Peritoneal mesothelioma

Surgical options: Sometimes, surgery is offered to reduce the amount of disease in the abdomen. A special type of chemotherapy may be administered into the abdomen to further reduce the number of cancer cells.¹²

Non-surgical options: If you are not well enough to undergo surgery or do not wish to have it, you may be offered chemotherapy alone.¹²

Testicular and pericardial mesothelioma

There has been little specific scientific research into the best ways to treat testicular and pericardial mesothelioma. Treatment usually involves a combination of surgery, chemotherapy and/or radiation therapy.^{8, 9}

Complications

Possible complications depend on the type of malignant mesothelioma a person has and what treatment they are receiving. It can be helpful to divide possible complications into the following groups:

1. Complications from mesothelioma itself: Mesothelioma can spread, either to distant parts of the body or to nearby structures.¹⁰ The consequences of any spread will depend on where the cancer spreads. Like with many cancers, the risk of blood clots is increased.¹⁴
2. Complications from treatment: Chemotherapy can lead to abnormalities of the blood. You may be given vitamins along with your chemotherapy to reduce the risk.¹⁵ Radiation therapy can lead to inflammation in the part of the body being treated⁶ and can lead to fatigue or vomiting. Different surgical procedures will carry individual risks. Speak to your healthcare provider to learn more about possible complications of any treatment you have been offered.

Prognosis

The prognosis (how well you are expected to do after receiving a diagnosis) of malignant mesothelioma depends on which type of disease a person has. Data from the Moffitt Cancer Centre suggests that the overall 5-year survival rate (percentage of patients alive 5 years after being diagnosed) is as follows:

Pleural mesothelioma: 12%

Peritoneal mesothelioma: 65%

Pericardial mesothelioma: 9%

The 5-year survival rate for testicular mesothelioma is 49%.¹⁶

Summary

Malignant mesothelioma is a rare cancer, most commonly affecting the tissue covering the lungs (pleura). It is more common in older people AMAB with a history of asbestos exposure. 

Symptoms, treatment options and survival rates depend on which part of the body is affected. Surgery is an option for some people. Non-surgical treatment options include chemotherapy and radiation therapy. 

If you are worried about symptoms or want to learn more about what treatment is best for you, speak to your healthcare provider.