Hi there Iam007 is correct most tumors show up on a scan unless the are super small (read micro scopic), in which case I would also wonder if they are visible to the naked eye at that point. Do get clarification - It is of the utmost importance that you are confident in the drs and treatment, and I too used to be a nurse and know that with so many fingers in the pot it's possible to miss something, so you need to advocate. Also a radiation oncologist needs a ct to work from to know where to focus the beam and design the radiation plan - so it is imperative that they know what they are talking about and what they're looking at.. your drs mistake is a little scary!

Good luck! And I'll say my prayers for your and your hubby.