- As part of this research study, two skin biopsies will be taken from each study site (at time of treatment, 6 months, and 12 months after AFT procedure only). A skin biopsy is a routine procedure which involves obtaining a very small skin sample (2-4 mm) with a special instrument (punch biopsy) that cuts out a small circular piece of skin. If needed, the area where the biopsy was taken may be closed with stitches.