I had symptoms of Behcet's for 20 years. it was mentioned to me several times and docs always said it was too rare. My immunologist tested me for it without me knowing what I was being tested for and I never mentioned most of the key symptoms to her. I have the genetic marker for it and most of the symptoms.
I was gluten free before they tested me for Behcet's. We have also done MRI's of my body for the ankylosing spondylitis and that is evident as well.
The doc wanted me to have the GI series and bowel study the next day. I couldn't do it for 4 days because I already had an MRI scheduled. I have responded well to the diet. I have heard that Behcet's should stay away from dairy. Have you ever heard of that?
I don't miss gluten at all, it is well worth it. Dairy I would miss! Is gluten challenge a gluten-free diet? Or is it something else? I haven't heard of that before.
Were you on the gluten challenge when they started thinking Behcets? A response to gluten can cause full body inflammation also. How have you responded to the diet? If you are responding well to the diet keep with it. False negatives on biopsy are not uncommon and since your biopsies were negative the doctor may be trying to rule out anything else. Try not to worry, if the doctor really thought you had lymphoma I think he would have those biopsies done quickly. Enjoy your holidays and try not to worry about it, hard I know as I have been there. Just stick strictly with the diet and I am hoping that will take care of your issues.