Histological responses of port wine stains in brown skin after 578 nm copper vapor laser treatment

Abstract Background and Objective The object of this study is to characterize the effects of epidermal melanin in brown skin on selective vessel damage by copper vapor laser radiation in port wine stain (PWS). Study Design/Materials, and Methods: We observed the histological changes of PWS in Korean patients who received copper vapor laser (578 nm) treatment over a range of energy densities (6–14 J/cm 2 ) and exposure durations (30–200 ms). The nitroblue tetrazolium chloride (NBTC) staining method was used to differentiate between the blue‐stained viable cells and the unstained thermally damaged cells. Results With Fontana‐Masson stain, we found that Korean skin has more epidermal melanin than Caucasian skin. For energy densities greater than 6 J/cm 2 , epidermal damage was observed. At 6 and 8 J/cm 2 , the damage to the dermis was localized to the blood vessels and the perivascular tissue. The connective tissue between damaged vessels and epidermis was still viable. Energy densities above 10 J/cm 2 produced a diffuse thermal necrosis. We conclude 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 , and the maximum penetration depth of these energy densities was 0.4 mm. We also found that the epidermal damage increased with increasing pulse widths at a fixed energy density (10 or 8 J/cm 2 ) while the severity 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. Conclusion 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. © 1996 Wiley‐Liss, Inc.