Cancer is not one disease but many, all with some similar features but all with a distinctive character which varies according to the cancer’s type and location.
There are over 200 types of cancer, but all start in the same way. Put simply, cancer is a disease of the cells. The control signals in a normal cell in the body go wrong, resulting in an abnormal cell. Cells normally divide and replicate themselves as a process of renewal, in a controlled way, but abnormal cells keep on dividing and this forms a lump.
The cluster of abnormal cells is called a tumour. Some tumours are benign, or harmless, and often don’t need treatment. 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. It is therefore possible to have a secondary breast cancer in the lung, for example.
What causes cancer and how quickly the cells grow and spread, is different from person to person. A large number of people with cancer overcome the disease, or live fulfilled lives for many years. A poor diet, lack of exercise, being over weight, smoking, heavy drinking, over exposure to the sun and hereditary factors can all contribute to causing cancer.