All cancers begin in cells. Our bodies are made up of more than a hundred million million (100,000,000,000,000) cells. Cancer starts with changes in one cell or a small group of cells. Cancer occurs when abnormal cells divide in an uncontrolled way. Some cancers may eventually spread into other tissues.
Usually we have just the right number of each type of cell. This is because cells produce signals to control how much and how often the cells divide. If any of these signals are faulty or missing, cells may start to grow and multiply too much and form a lump called a tumour. Where the cancer starts is called the primary tumour.
Some types of cancer, called leukaemia, start from blood cells. They don't form solid tumours. Instead, the cancer cells build up in the blood and sometimes the bone marrow. For a cancer to start, certain changes take place within the genes of a cell or a group of cells.
There are more than 200 different types of cancer. 1 in 2 people in the UK will get cancer in their lifetime.
Our bodies are made up of billions of cells. The cells are so small that they can only be seen under a microscope. These cells are grouped together to make up the tissues and organs of our bodies. These cells are basically the same, but they vary in some ways. This is because the body organs do very different things. For example, nerves and muscles do very different things. So nerve and muscle cells have different structures.
Cancers can be grouped according to the type of cell they start in. There are 5 main categories
Cancers can also be classified according to where they start in the body, such as breast cancer or lung cancer.
Knowing the symptoms of common cancers could make a real difference. Usually, the earlier cancer is found, the more likely it is to be cured. Below are some of the most common cancers in the UK.