From one point of view, there are as many types of cancer as there are different people, because everyone's genes are different and so no two cancers are exactly alike.
From another point of view, there are as many different types of cancer as there are different types of human cell - just over 200.
However, cancers can be broadly grouped into different types, depending on which tissues they come from.
These terms often have prefixes that describe exactly what type of cell the cancer originated from. For example, an osteosarcoma is a cancer of the bone.
Since the first draft of human genome was published in 2002, a huge international effort began to classify all the genes involved in cancer. One day soon, doctors may be able to do a quick genetic test on a patient's tumour to determine exactly what genes have gone wrong. They could use this information to work out precisely the right treatment to give the patient, and saving even more lives than they do already.