Cancer is not a single disease but a range of about 200 different conditions caused by collections of abnormal cells dividing uncontrollably. Cancer is second only to diseases of the heart and blood vessels as a cause of death. The word ‘tumour’ is often confused with cancer but actually only means a growth that may or may not be malignant. In other words, it may be ‘benign’, that is non-cancerous, and unable to spread to other parts of the body or recur. All cancers primarily affect older people.

Malignant tumours are the real cancers and they behave quite differently from benign tumours. There are two broad classes of cancers. Those that arise from surface linings of organs are the commonest group and are called carcinomas. The second group called sarcomas, arise from the substance of solid tissues such as muscle, bone, lymph glands, blood vessels and fibrous and other connective tissues. Sarcomas are generally much less common than carcinomas. Both carcinomas and sarcomas are able to invade normal tissue and spread through the body.

Throughout nearly all the tissues of the body, there are thin-walled tubes called lymphatic ducts. Their job is to carry off excess fluid from the tissues back to the bloodstream. Lymphatic ducts are very easily invaded by cancers, and this is a very common way for cancer cells to spread.

Cancers vary greatly in the speed with which they spread. Tumours of high malignancy will sometimes have spread widely before they are diagnosed.

Cancer has many causes and not all are known. There are certain general guidelines, however, which help reduce your risk from cancer.

Most cancers appear to be caused by a combination of factors including smoking, diet, sunlight, environmental factors, and inheritance.

The evidence linking cancer of the lung, for instance, to cigarette smoking is now overwhelming. But smoking can also cause cancer of the tongue and bladder and various other organs. The cancer-producing substances in cigarette smoke are absorbed into the blood and get everywhere in the body.

Similarly, excessive exposure to sunlight and regular contact with substances such as soot, tar, creosote, pitch and various mineral oils are known to cause skin cancer. See sections on specific cancers for information on their causes.

Cancer treatment varies with type and severity but there are three main types of treatment method:

Surgical removal is the main treatment for most solid tumours, especially when the cancer is in the early stages and has not spread to other areas of the body. Some surrounding non-cancerous tissue may also be removed to prevent a recurrence, as well as any lymph nodes near the tumour.

Treatment with anti-cancer drugs either by mouth, or more commonly by injection into a vein

Radiotherapy aims to destroy cancerous cells by bombarding them with radiation. The dose and siting of the radiation is carefully controlled so as not to harm healthy tissue.