HISTOLOGICAL RESPONSES OF PORT-WINE STAINS IN BROWN SKIN AFTER 578-NMCOPPER-VAPOR LASER TREATMENT

Background and Objective: The object of this study is to characterize the effects of epidermal melanin in brown skin on selective vessel dam age by copper vapor laser radiation in port wine stain (PWS). Study De sign/Materials, and Methods: We observed the histological changes of P WS in Korean patients who received copper vapor laser (578 nm) treatme nt over a range of energy densities (6-14 J/cm(2)) and exposure durati ons (30-200 ms). The nitroblue tetrazolium chloride (NBTC) staining me thod was used to differentiate between the blue-stained viable cells a nd the unstained thermally damaged cells. Results: With Fontana-Masson stain, we found that Korean skin has more epidermal melanin than Cauc asian skin. For energy densities greater than 6 J/cm(2), epidermal dam age was observed. At 6 and 8 J/cm(2), the damage to the dermis was loc alized to the blood vessels and the perivascular tissue. The connectiv e tissue between damaged vessels and epidermis was still viable. Energ y densities above 10 J/cm(2) produced a diffuse thermal necrosis. We c onclude that vascular selectivity without epidermal damages cannot be achieved with a 50 ms exposure at 578 nm in the brown skin of Koreans. The energy density for clinical minimal whitening was 6-8 J/cm(2), an d the maximum penetration depth of these energy densities was 0.4 mm. We also found that the epidermal damage increased with increasing puls e widths at a fixed energy density (10 or 8 J/cm(2)) while the severit y and depth of vascular damage decreased. These findings suggest that it is best to treat PWS with a copper vapor laser at the minimal pulse width and maximal power output possible at given energy density. Conc lusion: We have demonstrated that the copper vapor laser treatment of PWS in the brown skin is not as selective as in white skin because of epidermal melanin. (C) 1996 Wiley-Liss, Inc.