Histologic features seen in changing nevi after therapy with an 810 nm pulsed diode laser for hair removal in patients with dysplastic nevi

Background The majority of lasers used for hair removal target melanin as t he chromophore. In contrast with other cutaneous applications of lasers, la sers used for hair removal must generate a limited, controlled degree of th ermal damage to permanently remove hairs. Aim To remove excess back hair from two male patients, one with a history o f multiple nevi, and prior biopsies showing features of dysplastic nevi, an d the other with large nevi greater than 6 mm in diameter and a family hist ory of malignant melanoma. Methods Both patients received monthly treatments with an 810 nm, pulsed, h igh-power diode laser using a fluence of 20 J/cm(2) and 25-30 J/cm(2), resp ectively, and a pulse duration of 30 ms. Results Both patients presented 1 month after their last treatment with cha nging nevi within the treatment areas. Neither patient had clinical inflamm ation or other alterations suggestive of change in the nevi related to trea tment. Thus, the nevi were excised with no mention of the previous laser tr eatment. The histologic features in all nevi were similar. There was subepi dermal blister formation with elongation and disruption of nevus cells. The re was homogenization of the collagen within the papillary dermis in all le sions. Only small foci of nevus cells could be identified in the dermis in some of the biopsy specimens. In these biopsy specimens, the dermal stromal matrix homogenization extended into the reticular dermis. Conclusions Laser targeting of nevus cells and surrounding structures may p roduce clinically atypical nevi in areas previously treated for hair remova l. This should be kept in mind, especially in patients with a history of dy splastic nevi or with a personal or family history of malignant melanoma.