Hello, I Have A Question About A CT Scan... My

Hello, I have a question about a CT scan... My husband was diagnosed with metastatic testicular cancer a couple years ago, long story short, he had a tandum stem cell transplant which was a miracle because he has been cancer free for about 18 months now. It is time for a routine CT scan and labs and the Dr. mentioned that there were some grey areas but his labs are excellent, should I be worried. What do the grey areas mean? I read that they grey areas are just organs. Is this correct?