MACMILLAN CANCER APPEAL: EVERYONE has heard of cancer, most people know someone affected by it, but not so many actually know what the disease is.

Cancer is not one disease but many, all with some similar features but also with distinctive characteristics, which vary according to the cancer type and location.

The most common types of cancer are listed in the two tables opposite.

There are more than 200 types of cancer, but all start in the same way. The control signals in a normal cell in the body go wrong, resulting in an abnormal cell.

Cells normally divide in a controlled way, but abnormal cells keep on dividing, which can form a lump.

This cluster of abnormal cells is called a tumour.

Some tumours, or lumps, are benign, which means they are not cancerous. Depending on where they are in the body, and whether they keep on growing, some of these benign tumours may have to be removed while others may be harmless.

But malignant tumours the cancers can spread.

They may be dangerous because they can invade nearby parts of the body and stop them working properly.

Cells from malignant tumours can break away and travel to other parts of the body, where they can form new groups of abnormal cells, called secondary growths.

What causes cancer in the first place, and how quickly the cells grow and spread, is different from person to person.

The most common causes of cancer are environmental factors such as tobacco, sunshine, diet or viruses. A less common cause is hereditary genetic factors, where genetic faults are inherited from our relatives.

Making improvements to lifestyle diet, not smoking, drinking alcohol in moderation, exercise and protection from the sun will help reduce the risk of developing cancer.

It is also important to be aware of warning signs that may indicate the early stages of a cancer, such as changes to a mole or the appearance of a lump, and to participate in NHS screening programmes.

These may lead to the detection of a cancer at a stage when it is easily treated, such as through minor surgery.

A large number of people with cancer overcome the disease and live fulfilled lives for many years.

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