Cancers used to be defined by where they grow in the body – lung cancer, skin cancer, brain cancer, etc. But work in recent decades has shown that cancers sharing specific genetic changes may have more in common than cancers that happen to grow in an area of the body. For example, lung cancers, skin cancers, and brain cancers may all be caused by mutation in a gene called BRAF. And drugs targeting BRAF have changed the treatment landscape for melanoma, an aggressive form of skin cancer, and are also in use against lung cancers and brain cancers with BRAF mutations.