RESUMEN
BACKGROUND: Photodynamic therapy (PDT) is an established treatment for basal cell carcinomas (BCCs). Although recurrences are sometime observed, their histological patterns have never been specifically studied or compared with the one of the initial tumor. OBJECTIVE: To compare the histopathological aggressiveness of BCCs recurring after PDT with that of the primary tumors. METHODS: The study population included 12 patients with 16 post PDT recurrent BCCs. Outcome measures were proportion of histologically aggressive subtypes in BCC recurrences vs. primary tumor. RESULTS: 62.5% of recurrent BCCs displayed a transition from a non-aggressive to an aggressive subtype. CONCLUSIONS: Post PDT recurrences appear to display an increased histological aggressiveness, although the latter may reflect the natural course of tumor progression. Despite the presence of potential biases, our study raises the possibility that PDT favors the selection of more aggressive tumor cells. Better systematic large-scale follow-up studies are required to assess the exact frequency and histological types of BCC recurrences after PDT.