Cancer

Causes of cancer

Cancer is a chronic disease. As with any other chronic diseases, cancer has a multifactorial etiology (cause). Carcinogens are the substances which can cause cancer to humans.

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.

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Cancer: a General understanding

Cancer can be regarded as a group of most serious diseases which are characterized by (1) abnormal growth of cells without control. (2) ability to invade nearby tissues and even to distant organs, by local invasion, through lymphatic system and blood. (3) the eventual death of patient it the tumor (cancer) has progressed beyond the stage when it can be successfully removed by surgery . Cancer can occur at any site of the body and it can involve any type of cells.

If cancer occurs in a tissue, the cells of the tissue starts growing abnormally fast. But the cells can not mature and because cells are not mature they cannot perform the function for which they are present in the body. For example if there is cancer of liver (hepatocellular carcinoma) the cancerous liver cells cannot perform functions of liver, but they consume the nutrition and due to large number and fast growing they consume large number of calories. This is the reason of weight loss in cancer. These immature cells keeps growing in number without any function and may spread to nearby tissues or to a distant site through blood. One cancerous cell is enough for spread to distant organ which keep growing very fast.

Cancer can be categorized into the following major categories:

1. Caremomas :They arise from epithelial cells which is the cell lining the surface of various organs like mouth, uterus, intestines, stomach, inner side of nose etc, This type may arise from skin also from skin epithelium .
2. Sarcomas :They arise from various cells which constitute connective tissues like bone, fat, fibrous tissues, bran tissue etc.
3. Lymphomas, myelomas and leukemias (blood cancer) arise from the cells of immune system as well as from bone marrow. Blood cancer or leukemia arise from bone marrow, because blood cells are formed in bone marrow.

In blood cancer (leukemia) white blood cells, whose main function is to fight with the invading microorganisms (bacteria, virus, fungus etc), starts growing abnormally rapidly in bone marrow but they are not mature. Because of immaturity they can not perform their primary function, which is to fight with invading microorganisms. And patient eventually die due to infection.

The term primary (cancer) tumor means cancer in the organ of origin, but secondary (cancer) tumor means the cancer which has spread to distant organ or to regional lymph nodes. When cancer cells multiply and reach a critical size cancer can be clinically evident as mass or ulcer in the particular area. Some time primary tumor can not be detected or found, but the secondary tumor became the main cancer. In this type of cases the primary tumor shrinks due some reason and become undetectable.