RESUMO
Photodynamic therapy involves - in dermatological practice usually exogenous - application of a photosensitizer then activation of accumulated protoporphyrin IX by light with an appropriate wavelength after a short incubation period. It is an evidence based method to treat certain non-melanoma skin cancers. During treatment when the excited protoporphyrin IX returns to base state, reactive oxygen species are formed leading to cell death in rapidly proliferating cells. Fluorescence of excited protoporphyrin IX can be used in diagnostics as well. In ultraviolet light, the photodamaged or neoplastic areas show coral red fluorescence which can clearly be distinguished from the much lower fluorescence of adjacent normal tissue. This process is suitable for exact determination of tumor margins so it can be used for planning surgical procedures or after photodynamic therapy at a follow up visit for the visualization of the therapeutic result. The present article reviews the literature of photodynamic diagnosis that is also used by the authors.