It seems like the CT/PET scans are the gold standard for diagnosing cancers so if nothing lights up there is probably isn't anything or at least not cancer. They really studied the MRI results where the doctor who read it thought what he saw was consistent with bone cancer, compared it to his many previous CT/PET scans and saw the same thing, but it wasn't growing or doing anything and it didn't light up on the May CT/PET scan - so not cancer.
Michael's oncologist says that if you keep looking for things that you will eventually find abnormalities in all of us which may not be anything major or anything that needs treatment. Good luck