Mesothelioma is a type of cancer that is usually caused by exposure to asbestos. According to Mesothelioma UK around 2,500 people are diagnosed with this asbestos cancer every year.

People who have been exposed to asbestos are potentially at risk of mesothelioma, however the majority of people who have been exposed to asbestos dust never suffer any ill health. >Read more about why asbestos is dangerous and the illnesses it can cause here.

Mesothelioma facts

What is mesothelioma?

Mesothelioma is a type of cancer that affects the mesothelium, which is the membrane that forms the lining of the chest wall, where it’s known as the pleura, and the abdomen, where it is known as the peritoneum.

Pleural mesothelioma is far more common than pleural mesothelioma, with a ratio of 12 to 1.

Stages of mesothelioma

How far cancer has spread is referred to as stages. Knowing what stage cancer is at helps doctors to decide on what treatment is needed. Unfortunately, most people who are diagnosed with mesothelioma have an advanced stage of cancer and the prognosis is not good.

It is difficult for medical professionals to stage mesothelioma because the tumour is not often measurable.

Pleural mesothelioma stages

As pleural mesothelioma is the most common form of mesothelioma there is an internationally recognised staging system; the International Mesothelioma Interest Group (IMIG) system. The IMIG system is based on the generic TNM system. The staging system is used to describe; the size and position of the mesothelioma primary tumour (T), whether the cancerous cells have spread to nearby lymph nodes (N), and whether the mesothelioma cells have spread to elsewhere in the body, known as metastases (M). This information is used to give a stage: stage 1 is the earliest and stage 4 the most advanced.

Stage 1a mesothelioma

The cancer is only affecting the outer layer of pleura around the chest wall and only on one side of the chest. The tumour may have grown into the pleura tissue that covers the diaphragm.

Stage 1b mesothelioma

Mesothelioma has begun to spread into the pleural layer closest to the lungs on one side of the chest. Stage 1b mesothelioma has not spread into the lung tissue or diaphragm.

Stage 2 mesothelioma

Stage 2 is when the cancer has spread to both layers of the pleura on one side of the chest. It will have got big enough to form a tumour mass within the pleural tissue surrounding the lungs and started to spread into the diaphragm muscle or the lung tissue.

Stage 3 mesothelioma

The mesothelioma has spread to the chest wall or heart covering (pericardium), and may still be removable by surgery. Stage 3 may alternatively mean that the mesothelioma has spread to the lymph nodes on the same side of the chest.

Stage 4 mesothelioma

At the most advanced stage of mesothelioma, the cancer has spread too far to be operable.

This image from the American Mesothelioma Cancer Alliance illustrates the four stages:

Mesothelioma Tumor Progression

Image courtesy of the Mesothelioma Cancer Alliance.

Peritoneal mesothelioma stages

There is only one case of peritoneal mesothelioma for every 12 cases of pleural mesothelioma. Due to its rarity, there is no specific staging system for this type of mesothelioma. If it’s staged it’s likely to be done according to the TNM system that’s used for other types of cancers.

Click here to take a look at our Asbestos Awareness Online Course.

To find out more about mesothelioma, take a look at the Mesothelioma Prognosis Network – An advocacy group working to spread the awareness of asbestos related diseases. The organisation works with people affected by asbestos related illnesses to help find local doctors, treatment centres and support groups.