QUALITY-SWITCHED RUBY-LASER TREATMENT OF SOLAR LENTIGINES AND BECKERS-NEVUS - A HISTOPATHOLOGICAL AND IMMUNOHISTOCHEMICAL STUDY

Objective: A histopathological and immunohistochemical study was initi ated to assess changes in benign human pigmented skin lesions after qu ality switched ruby laser (QSRL) irradiation. Method: A total of 196 s olar lentigines on 8 patients' forearms were irradiated in vivo, 13 bi opsies were taken, Hematoxylin-eosin staining and immunohistochemical techniques using anti-S-100 and Fontana-Masson stainings, as well as c ryosections stained with nitroblue tetrazolium chloride (NBTC), were e mployed for the evaluation of the specimens. Results: Immediately afte r QSRL impact selective photothermal damage (vacuolization) of all pig mented epidermal and basal melanocytes, keratinocytes, superficial der mal melanocytes and melanophages could be observed in solar lentigines . Cryosections stained with NBTC featured minimal thermal damage of th e surrounding tissue. One Becker's nevus was also exposed to the QSRL, biopsies were taken before and immediately after QSRL exposure, In th is lesion, superficially located pigments were selectively damaged, bu t a fair mount of pigmented cells in adnexal structures persisted thro ughout this single course of QSRL treatment. Recurrence of lentigines was not observed, In Becker's nevus, following initial fading of the l esion, clinically reactive hyperpigmentation occurred 4 weeks later Co nclusion: We found that pigmented lesions featuring a moderate amount of pigment exclusively in and around the basal cell layer, like solar (actinic) lentigo, can be successfully removed by a single QSRL exposu re selectively damaging epidermal and basal pigmented structures. Furt her investigations concerning QSRL treatment of dermally pigmented ski n lesions have to be initiated.