Tests can help to confirm a diagnosis. They can also give the doctors more information about the size of the cancer and whether it has spread, so they can plan the best treatments for you.
Depending on the type of cancer, you may continue to need tests during and after treatment to see how well you are responding.
There are many types of test that show if someone has cancer or not. The types and numbers of tests will depend on the type of cancer the doctor thinks you may have.
You can find out more about how specific types of cancer are diagnosed in our Cancer types section.