Background: Vascular-targeted photodynamic therapy (PDT) is an effective alternative treatment choice for port-wine stains (PWSs). The histological characteristics of PWSs after PDT treatment have not yet been reported. Objective: To investigate the morphological features of PWSs treated by PDT and define the histopathological characteristics of PWS that achieve clinical cure. Methods: Thirteen patients with facial PWSs, who presented with complete regressive PWS lesions after a mean of 4.38 (standard deviation = 4.907) sessions of PDT. Post-treatment biopsy samples were obtained from each patient. The number of blood vessels, vascular diameter, and depth were measured and compared in all samples of PDT-regressive sites, PDT-resistant sites, and normal skin. Results: Within the 7-year follow-up after PDT, there was no recurrence in the regression area of PDT. In the PDT-regressive sites, within 800 μm of the dermal-epidermal junction, the dilated vessels were occluded and remained fissure-like after PDT. Conclusions: When the vascular lesions within 800 μm of the dermal-epidermal junction were closed after PDT, a stable clinical cure (no recurrence) was achieved.
Keywords: capillary malformation; efficacy; histopathology; photodynamic therapy; port-wine stain; regression; resistance.