- The lungs
- The role of the pleura
- Causes of pleural mesothelioma
- Symptoms of pleural mesothelioma
- Information reviewed by
The lungs are the main organs for breathing and are part of the respiratory system which also includes the nose, mouth, windpipe (trachea) and airways to each lung. They consist of large airways (bronchi) and smaller airways (bronchioles).
The lungs look like two large, spongy cones. Each lung is made up of sections called lobes – the left lung has two lobes and the right lung has three. The lungs rest on the diaphragm which is a wide, thin muscle that helps with breathing.
The chest wall and lungs are covered by two layers of a thin sheet of tissue called the pleura.
The inner layer (visceral pleura) lines the lungs, while the outer layer (parietal pleura) lines the chest wall and the diaphragm.
Between the two layers is the pleural cavity (also called the pleural space) which normally contains a small amount of fluid. This fluid allows the two layers of pleura to slide over each other so the lungs move smoothly against the chest wall when you breathe.
When mesothelioma develops in the pleura, the delicate layers of the pleura thicken and may press on the lung, preventing it from expanding when breathing in. When excess fluid collects between the two layers it is known as a pleural effusion.
Mesothelioma is a type of cancer that starts from mesothelial cells. These cells line the outer surface of most of the body’s internal organs, forming a membrane called the mesothelium. The membrane that covers the lungs is the pleura.
Mesotheliomas are unusual as they only form metastases in the later stages of the disease process. They usually spread by invading adjacent organs and structures in the chest and abdomen, and to the lymph nodes in the chest.
There are two main types of mesothelioma which are classified according to the area affected.
- Pleural – this forms in the covering of the lungs. Pleural mesothelioma is the most common type accounting for about 90 per cent of all mesotheliomas. This type of mesothelioma is called malignant pleural mesothelioma (MPM). Here we refer to it as pleural mesothelioma or, simply, mesothelioma.
- Peritoneal – this develops in the lining of the abdomen. It accounts for about 10 per cent of cases and is called malignant peritoneal mesothelioma.
Rarely mesothelioma occurs in the pericardium (the membrane around the heart) or the tunica vaginalis (the membrane around the testicles).
Although pleural mesothelioma develops in the chest and involves the lining of the lungs it is not lung cancer and is diagnosed and treated differently.
Cell types of mesothelioma
Mesothelioma is also grouped according to how the cells look under a microscope. There are three main types:
- epithelioid – cells look similar to normal mesothelial cells. This is the most common type making up about 60 per cent of cases
- sarcomatoid – cells have changed and look like cells from fibrous tissue. This accounts for about 15 per cent of cases
- mixed or biphasic – has epithelioid and sarcomatoid cells. These make up about 25 per cent of all cases.
Mesotheliomas can differ in the way they grow. Some form a mass; others grow along the pleura forming a thick covering on the lungs.
Exposure to asbestos is generally the only known cause of mesothelioma. Sometimes mesothelioma is linked with previous radiotherapy to the chest.
Asbestos is the name of a group of naturally occurring minerals resistant to high temperatures and humidity. It was used in many building products in Australia from the 1940s until 1987.
People most likely to have been exposed to asbestos at work include asbestos miners and millers, transport workers (especially waterside workers), insulators, builders, plumbers and electricians, mechanics and asbestos cement manufacturing workers.
People who haven’t worked directly with asbestos but have been exposed to it can also develop mesothelioma. This can include people washing or cleaning work clothes with asbestos fibres on them or people renovating homes.
It can take many years after being exposed to asbestos for mesothelioma to develop. This is called the latency period or latent interval and is usually between 20 and 60 years.
People who develop mesothelioma due to asbestos exposure may be able to claim compensation. It’s important to get legal advice from an experienced lawyer as soon as possible after diagnosis.
For further information on legal advice, visit ReturnToWorkSA: rtwsa.com
Shortness of breath (breathlessness)
Most people with pleural mesothelioma experience breathlessness. You may feel like you can’t catch your breath no matter what you do. It usually feels worse with activity or when you are lying down. In early mesothelioma breathlessness is caused by a build-up of fluid in the chest (pleural effusion).
This can be a sharp pain in the chest which affects your breathing or a dull pain in the shoulder and upper arm. The pain might not improve with pain relievers.
Other general symptoms
Less commonly people notice loss of appetite and weight loss, a persistent cough or a change in their coughing pattern. Some people also experience heavy sweating especially at night.
Information last reviewed June 2015 by: Theodora Ahilas, Principal, Maurice Blackburn Lawyers, NSW; Shirley Bare, Support Group Facilitator, Asbestoswise, VIC; Geoffrey Dickin, Consumer; Victoria Keena, Executive Officer, Asbestos Diseases Research Institute, NSW; Angela Kyttaridis, Social Worker, Concord Repatriation General Hospital, NSW; Jocelyn McLean, Mesothelioma Support Coordinator, Asbestos Diseases Research Institute, NSW; Kirsten Mooney, Thoracic Cancer Nurse Coordinator, WA Cancer and Palliative Care Network, Department of Health, WA; Clin/Prof AW Musk AM, Schools of Population Health and Medicine, University of Western Australia, and Physician, Sir Charles Gairdner Hospital, Nedlands, WA; Dr Andrew Penman AM, Consultant, Asbestos Diseases Research Institute, NSW; Tanya Segelov, Partner, Turner Freeman Lawyers, NSW; Roswitha Stegmann, 13 11 20 Consultant, Cancer Council Western Australia, WA; Dr Mo Mo Tin, Staff Specialist Radiation Oncology, Chris O’Brien Lifehouse, NSW; and Prof Nico van Zandwijk, Director of the Asbestos Diseases Research Institute and Professor of Medicine, University of Sydney, NSW.