Have the doctors done a bronchoscopy on him. this is where they actually take a piece of lung from a person and test it. If the CT and MRi failed to reveal anything, then I would go with the Dr's findings. Usually if there is anything, those tests will see it. They are pretty accurate. Sometimes, tests like these don't always pick up everything and then that's when a doctor will do the scope. They are not done very often. Mostly because they are uncomfortable. I do know a person who has to have one done every year because of what her father had and I don't quite understand the entire process. Honestly, If all those test didn't show any cancer, then you should be satisfied with that. It sounds like his Dr's have taken the proper course of tests for him. There is no cancer. Be glad. The little spot doesn't seem to be of concern to the doctor. If your dad's not happy, he can always get another opinion. but like I said, I believe the tests. Good luck