The tumor was/went/remained 'undetected' for years.
No one can slip by the guards 'undetected'.
(..) You asked me once why I married your mother. I married her because I loved her. Whatever the case we need to get aboard Nero's ship undetected. Just can't just go in there guns blazing, Jim. I'm telling you to... - Captain Kirk. Captain Kirk. - Yes, Chekov. What is it? (..)2009 Star Trek