Can you clarify what cancer really is?

Cancer. A neoplasm occurs when the "switches" in our cells that normally regulate cell proliferation and cell death are not functioning properly on a molecular level (for a variety of reasons). As a result, cell growth is uncontrolled, and a tumor develops. A neoplasm is deemed "malignant" when it has the ability to invade surrounding tissues and spread via lymphatic/blood vessels.
Loss of normal. Controls on cell growth, and regaining cell functions that may have been appropriate during development, but are inappropraite and harmful once these cells have become committed cells joined to a system. So, the originating organ grows a mass, and cells travel undetected to infest other organs ruining their function. All require genes. Eg, one mutant gene (bcr-abl) make a drug (imatinib) target.
Million dollar ???? The general idea is that cancer is a collection of cells that are growing out of control and eventually prevent other organs from doing their job which leads to signs and symptoms of the illness. Oddly, the abnormal c cells are assisted though by seemingly normal parts of the body having additional damage, e.g. Cancers of blood cells are assisted by abnormal interactions with other organs...