A good overview of the cancer genome and how technology has aided in it's discovery can be found in a review article completed by Michael R. Stratton Nature 2009

Cancer is a complex disease that can be the result of many different mutuations in a genetic sequence of an organsim. The genome of cancer cells will be different depending on the caner type and the tissue type the cancer is invading. Knowing the genome of a general cancer cell can help prevent exposure to substances that may cause certain mutations and can aid in designing treatment plans for affected individuals.