Welcome to BYC. I am not an expert on chicken necropsies or butchering, but I would do some research about possible Mareks disease, since I think it can cause white lumps or tumors on the intestines. Did you take any pictures? If you Google Mareks disease, go up to images, and look through the pictures. I will try to link some when I am on my computer in the AM.
I found the link I was looking for. If you Google "atlas of avian diseases" you will come upon Cornell University's site. Enter Mareks disease under "view all disease" names, and go to "gross lesions." Go to photo #49 for a picture of white tumors on intestines.