Any khnown registered person in the usa or even the world who got cancer or tumor from a ct scans radiation years later ? any known case?

Difficult to say: The risk we we give for x-ray exams (x-ray, ct, mammo, fluoro, etc) is based on extending the information from the atomic bombs of world war ii. We do not have a 100% accurate way to figure out your risk. Also, we do not have a way to figure out the exact reason for most cancers. We give an estimate (a guess) as to the risk. However, the risk is almost always outweighed by the diagnosis.

Yes: This is a well-known entity and has resulted in efforts to minimize the use of ct scans, especially in children. The exposure is gradual and accumulates over many years, which is why children are at the greatest risk. Before you have a ct scan, talk with your doctor to make sure it is really necessary and see if there are any alternatives, like MRI which do not use radiation.

Probably: But not exactly. A large scale study showed an increased incidence of cancer a group that had more cts than control group but no more direct evidence than that. Of note, this was in children and they were from scanners dating many years back and the cumulative doses they received were very large by today's standards. Should you be wary, yes but i would not avoid a necessary scan.