It is not an infection (although in a few cases it can be caused by a viral infection) but the result, in all probability, inherited weakness in the genetic makeup, with poor living habits and surroundings. Unhealthy diet, smoking, prolonged stress, and industrial pollution, for example, are either known to be, or are strongly suspected of being, main contributory or risk factors in cancer.

The human body contains more than of some coupled 200 different types of cell, which means there are more than 200 different types of cancer. An abnormal growth may be called a tumor or a neoplasm (neo simply means "new" and plasm means "form"). A resulting illness is known as a neoplastic disorder.

If the tumor or growth is purely local and not invasive it will be described as benign. A benign growth does not spread, so is less damaging. Examples are warts, cysts, and polyps. A growth that cannot be contained and continues to spread unchecked is known as a malignant growth. This is cancer.

Medical terms given to the different sorts of cali relate to where they are growing in the body:

Carcinoma is cancer of the skin covering the outside of the body and the mucous membrane lining the cavities within (epithelial tissue). This is by far them common type of cancer and includes cancers of the, breast, lung, colon, prostate, and skin. The most serious form of skin cancer is melanoma.

Sarcoma is cancer of the bones, tendons, muscles.

Lymphoma is cancer of the glands (or nodes) or other parts of the lymphatic system

Leukemia is cancer of the blood.

Cancer differs from country to country and from region to region. Some types of cancer are more communi Western countries, such as North America and Europe, than in Eastern countries, such as Japan, or so-called developing countries such as Africa. In Japan, for example, there are many more cases of stomach cancer than there are in the West, and in Africa liver cancer is much more widespread than elsewhere. Overall, the ten most common cancers found worldwide are of the lung, stomach, breast, lower bowel, cervix, mouth, lymphatic system, liver, throat, and prostate gland. None of the therapies described offers a cure for cancer but they can alleviate symptoms and support the immune system.