We previously reported similar findings in Bowen's disease patients treated with MAL-PDT and in the SCC cell lines SCC-13 and A-431.[27] Furthermore, the findings of multiple in vivo studies suggest that p53 may play a role in the observed increase in PpIX levels and subsequent cell death with increased selective accumulation.[28–31]. The gene discussed is TP53; the disease is Bowen disease of the skin.