Ulcers and Tumors confused??

We found out my husband has colon cancer last christmas they moved on him quickly removed his gallbladder and half of his right side colon , he has done some of his chemo but had trouble with blood and platlet counts going to low, so we had an other PET scan and was told he had a tumor on his intestine and pancreas, which he will need a WHIPPLE surgery. In the mean time he has had losts of pain vomiting, went in to the hospital found an ulcer in the same area as the tumor, feeding tube was placed meds were given, we came home to heal before the surgery, my husband has recieved a call from the Dr, saying now he has a ulcer not tumor???? Has this happened to anyone else?? Where the pet scan has picked up on somethinng else??