My son had a biopsy - the dermatologist took part of a peel on his lips - she did not dig into the lip. It did come back as yeast and an infection - he is taking medication now for yeast and putting antibacterial ointment on his lips - he has had this for about a year and a half - he still has another week on the medication.
We didnt do a biopsy before because most people on here that I have read about have NOT had yeast - so I was suprised that is was listed as yeast. We think he got his from taking Acne medication which can cause overgrowth of yeast.
We hope this cures it - but dont' know yet - I would recommend going to a dermatologist to do a biopsy. But, most people that have this have not found yeast from what i have read.