Mesothelioma, more precisely malignant mesothelioma is a rare type of cancer. Malignant (cancerous) cells develop in the mesothelium, the protective sac that covers most of the body’s internal organs. Mesothelioma generally starts in the outer membrane of the lungs (pleura), but can also occur in the lining of the abdominal cavity (peritoneum). Uncommonly, the heart or reproductive organs may be affected. Treatment depends on where the cancer is found and whether it has spread.
Mesothelioma is almost always caused by exposure to asbestos and can develop decades after the exposure.
Mesothelioma is caused by asbestos exposure. Asbestos, once regarded as a miracle mineral, was popular due its lightweight but tough characteristics as well as for its heat-resistant properties. This naturally occurring mineral was used in many commercial and consumer products, from construction materials such as cement, roofing shingles and insulation, to consumer and industrial applications such as hair dryers, automobile brake pads and pipe insulation.
Most people with malignant mesothelioma worked on jobs where they breathed asbestos. Others were exposed to asbestos in a household environment, often without knowing it.
What happens inside the body?
The cancerous cells clump together in a malignant tumour. As it grows, the tumour pushes against and into other organs and healthy tissue, causing symptoms. Because the mesothelium is a flat thin lining, the mesothelioma tumour often takes a diffuse shape.
In its advanced stage the cancer metastasizes through the lymph system and spreads to other parts of the body. It is still referred to as mesothelioma because it started in the mesothelium.
How it spreads?
Malignant (cancerous) cells develop in the mesothelium. This protective sac has different names, depending on its location in the body. Those most commonly affected by mesothelioma are:
- Visceral pleura – the membrane that surrounds the lungs
- Parietal pleura – the membrane that lines the chest wall
- Peritoneum – the membrane that forms the lining of the abdominal and pelvic cavities.
Mesothelioma most often starts in the pleura. Normally, the two pleura touch and slide across each other while we breathe, lubricated by a slick of fluid. In cases of pleural mesothelioma, the pleura make more fluid than necessary, which presses on the lung (pleural effusion). Mesothelioma usually develops in only one lung. The tumour tends to grow across the lung until the entire organ is encased.
In about 10 per cent of mesothelioma cases, asbestos fibres that have been swallowed can move through the stomach wall and cause cancer cells to develop in the peritoneum (peritoneal mesothelioma).
Sometimes cancer cells migrate to lymph nodes and other areas of the body (such as the unaffected lung) via the lymphatic system. Uncommonly, the heart or reproductive organs may be affected.
Symptoms or signs of mesothelioma may not appear until 20 to 50 years (or more) after exposure to asbestos. Shortness of breath, cough, and pain in the chest due to an accumulation of fluid in the pleural space (pleural effusion) are often symptoms of pleural mesothelioma.
Symptoms of peritoneal mesothelioma include weight loss and cachexia, abdominal swelling and pain due to ascites (a build-up of fluid in the abdominal cavity). Other symptoms of Peritoneal Mesothelioma may include bowel obstruction, blood clotting abnormalities, anaemia, and fever. If the cancer has spread beyond the mesothelium to other parts of the body, symptoms may include pain, trouble swallowing, or swelling of the neck or face.
These symptoms may be caused by mesothelioma or by other, less serious conditions.
Mesothelioma that affects the pleura can cause these signs and symptoms:
- Chest wall pain
- Pleural effusion, or fluid surrounding the lung
- Shortness of breath
- Fatigue or anaemia
- Wheezing, hoarseness, or cough
- Blood in the sputum (fluid) coughed up (haemoptysis)
In severe cases, the person may have many tumour masses. The individual may develop a pneumothorax, or collapse of the lung. The disease may metastasize, or spread, to other parts of the body.
Tumours that affect the abdominal cavity often do not cause symptoms until they are at a late stage. Symptoms include:
- Abdominal pain
- Ascites, or an abnormal build-up of fluid in the abdomen
- A mass in the abdomen
- Problems with bowel function
- Weight loss
In severe cases of the disease, the following signs and symptoms may be present:
- Blood clots in the veins, which may cause thrombophlebitis
- Disseminated intravascular coagulation, a disorder causing severe bleeding in many body organs
- Jaundice, or yellowing of the eyes and skin
- Low blood sugar level
- Pleural effusion
- Pulmonary emboli, or blood clots in the arteries of the lungs