Quality-switched ruby laser treatment of solar lentigines and Becker's nevus: a histopathological and immunohistochemical study.

OBJECTIVE

A histopathological and immunohistochemical study was initiated to assess changes in benign human pigmented skin lesions after quality switched ruby laser (QSRL) irradiation.

METHOD

A total of 196 solar lentigines on 8 patients' forearms were irradiated in vivo, 13 biopsies were taken. Hematoxylin-eosin staining and immunohistochemical techniques using anti-S-100 and Fontana-Masson stainings, as well as cryosections stained with nitroblue tetrazolium chloride (NBTC), were employed for the evaluation of the specimens.

RESULTS

Immediately after QSRL impact selective photothermal damage (vacuolization) of all pigmented epidermal and basal melanocytes, keratinocytes, superficial dermal melanocytes and melanophages could be observed in solar lentigines. Cryosections stained with NBTC featured minimal thermal damage of the surrounding tissue. One Becker's nevus was also exposed to the QSRL, biopsies were taken before and immediately after QSRL exposure. In this lesion, superficially located pigments were selectively damaged, but a fair amount of pigmented cells in adnexal structures persisted throughout this single course of QSRL treatment. Recurrence of lentigines was not observed. In Becker's nevus, following initial fading of the lesion, clinically reactive hyperpigmentation occurred 4 weeks later.

CONCLUSION

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 exposure selectively damaging epidermal and basal pigmented structures. Further investigations concerning QSRL treatment of dermally pigmented skin lesions have to be initiated.