i guess so, but cancer is testable, due to abnormal growth in cells, so what they do is sometimes they give you this IV that has a slightly radioactive substance in it, then they let it circulate in your system and then take an image of it. The areas that have a high concentration of it usually mean that there is abnormal growth there, which usually indicates cancer. Cancer is also indicated by an abnormal lump or growth. i.e a lump in the breast ususally is breast cancer, so a mamography, or self-examination usually id's that, and a prostate exam usually tells if the prostate has cancer. To the best of my knowledge, mutations cannot be traced back to when they occurred, because it would be in the DNA, and that is multiplied many times over the same day, so it probably cannot be traced. As to what type of mutation has occurred, in humans, it is usually traceable to what it does, because we have mapped the human genome. This means that they mapped the healthy version of the gene and if its mutated, then they can probably tell what it would change. Hope i helped you! =D