The commonest site of mesothelioma is the pleura, which is the outermost lining of the lungs and the chest wall. But mesothelioma can occur at any site where mesothelial cells lining is present like peritoneum, heart etc.

For a disease, the relationship of incidence to mortality rate is an indication of prognosis. Similar incidence and mortality rate is indication of essentially fatal condition. That is why lung cancer accounts for most deaths from cancer (1.1 million) in the world annually, because its incidence and mortality rate is similar and it is invariably associated with poor prognosis. On the other hand for breast cancer appropriate management can be effective in avoiding fatal out come. That is why although it is second in term of incidence but in terms of mortality it is ranked 5^th .

The basic approach to the control of cancer is through primary prevention and secondary prevention. It is estimated that at least one third of all cancers are preventable. If we analyze the causes of cancer it is seen that environmental factors are the most important in causation of cancer which are modifiable. Genetic factors which are not modifiable are responsible in small number of cases of cancer.

1. Environmental factors: Environmental factors are responsible for at least 90 per cent of all human cancers. The major environmental factors identified include the following:

a. Tobacco: Tobacco in various forms of usage (e.g. smoking, chewing, sniffing) is the major environmental cause of cancers of lungs, larynx, mouth, pharynx, esophagus, bladder, pancreas and also kidney. It has been estimated that cigarette smoking is responsible for more than one million premature deaths every year throughout the world in the form of cancer, respiratory problems and also in many other way. There is hardly any organ system which is not affected adversely due to cigarette smoking.