<s>[INST] My dentist discovered a red patch on the roof of my mouth about the size of my thumbnail. It is a little sore. I have post nasal drip and my throat feels sore. I am a pack a day smoker. I have been under a tremendous amount of stress and have been developing auto immune issues. Could this be oral cancer or auto immune issues? [/INST] Hi, Please stop smoking whatever this may turn out to be. The red area can be an ulcer/hyperemic area because of stress or problem with bowel. Or it can be premalignant condition and thus needs evaluation. Please use hexidine mouth wash and apply triamcinolone gel to that area and if it does not heal in few days, go to your ENT and may need a biopsy. Regards </s>