Radiation treatments will immuno suppress a patient, and if he already had pre cancer occurrences of canker sores this could be just another. There have been no definitive studies that show what happens to healing rates of post treatment hs virus that I can find. I am very sorry to panic you with my post. MY personal inclination in areas where little is known is to use the gold standard the biopsy. Of course post treatment the biopsy site can take a protracted period to heal after radiation treatments. But if your husband thinks that it is hurting less, getting smaller, etc. I would let things ride for a while before putting him through a procedure that he may not need. Again my apologies in not offering all perspectives. My view becomes tainted when I talk with patients in recurrence 2-3 times a week, and I should have included more information in my post to you. My personal opinion to you is that you watch it for another couple of weeks looking for signs of healing, if not complete healing. If it is a hs virus canker sore, there should be some progress. Confirm with your husband that he had these occasionally before cancer. That would do it for me, since hs virus sores manifest themselves when the immune system is suppressed, which after all the treatments your husband has been through, it certainly is. And with all respect to your doctor who is likely very competent, no one can tell that something is virally induced or if it is something worse, visually. He may have a very good eye and have seen lots of this, but this is always an educated guess, and not fact. Lets hope that over the next few weeks he proves to have that experienced eye that makes great educated, experience trained, assumptions.