For the second part: All patients will receive 4 PDT sessions 2 weeks apart using a light dose of 37 J/cm2. One treatment group will receive vehicle cream, while the other 2 groups will receive MAL cream with a concentration of 40 mg/g and 80 mg/g, respectively. The MAL and vehicle cream will be applied in a thin layer on clean skin and left for 1.5 hours under occlusion before illumination.