Cancer is not just one but many different diseases. Cancer occurs when abnormal cells, having accumulated different mutations, divide without control and are able to invade other tissues.

There are about 200 different types of cancer, but they all start as a result of the out-of-control growth of abnormal cells.

Cancers are classified in two ways: by the type of tissue in which the cancer originates (histological classification) or by the location or organ in the body where the cancer first developed.

Most people classify cancer based on the organ in which it starts - for example, cancer that begins in the colon is called colon cancer. However, physicians and health professionals use histological classification because it gives a better indication of how the cancer will behave. For instance, squamous cell carcinoma behaves similarly whether it originates from the lung or the prostate. For more information on the histology of different types of cancer, click here.

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