What is Mesothelioma?

In the United Kingdom almost 2000 people a year are diagnosed with mesothelioma. It is also known as ‘diffuse’ or ‘malignant’ mesothelioma. Mesothelioma is a form of cancer that affects the Mesothelium, which is a thin membrane that lines the inner surface of the chest wall where it is known as the pleura, and abdomen, where it is known as the peritoneum. It also surrounds the organs found within these cavities for example the heart, lung and intestines. It is far more common to have mesothelioma in the chest than in the abdomen, there is approximately 1 case of peritoneal mesothelioma to every 12 cases of pleural mesothelioma.

Pleural Mesothelioma

The pleural lining has two layers: the visceral (inner) layer is next to the lung and the parietal (outer) layer lines the chest wall. The pleura produces fluid that lubricates the space between the two layers, this allows the two layers to slide comfortably over each other as we breathe in and out. Pleural mesothelioma causes the pleura to thicken. This thickening of the pleura might begin to press onto the lungs or attach itself to the inside of the chest wall. In either case the expansion of the lung becomes progressively restricted by the tumour. Fluid, sometimes several litres, can collect between the two layers of the pleura; this affects the lungs ability to expand and causes the person to feel breathless. This is known as a pleural effusion.

Peritoneal Mesothelioma

The peritoneum also has two layers the inner (visceral) layer which is next to the abdominal organs and the outer (parietal) layer which lines the abdominal wall. Peritoneal mesothelioma causes the peritoneum to thicken and fluid to collect in the abdomen. This collection of fluid is called ascites and causes the abdomen to swell. Because pleural mesothelioma is more common and often spreads to the peritoneal cavity, it is sometimes necessary to determine if pleural mesothelioma is the primary cancer.