Selective photothermolysis of port-wine stains induced by Candela model SPTL-1P (577nm) and SPTL-1 (585nm) flashlamp pumped pulsed dye lasers were examined light and electron microscopically. Immediately after irradiation, red blood cells agglutination and heat necrosis were found at the dilated vessels in the dermis, and perivascular collagen fibrils necrosis was minimum. Twenty-four hours after irradiation, a lot of inflammatory cells were infiltrated around the necrotic vessels. One month after irradiation, the area in which dilated vessels had showed necrosis was replaced by granulation tissue. No recurrence or scar formation was observed in the dermis 6 months after irradiation. Comparing to SPTL-1P (577nm), SPTL-1 (585nm) showed deeper penetration in the dermis while the selectivity of vessel necrosis was not different between them. In the cases with epidermal hyperpigmentation, epidermal necrosis and reepithelization was found after irradiation. The reepithelized epidermis showed the state of pigment blockade for several weeks, and returned to normal pigmentation within 6 months.
