Clinical and histological responses of congenital melanocytic nevi after single treatment with Q-switched lasers
J. M. Grevelink, R. L. van Leeuwen, R. R. Anderson and H. R. Byers
Massachusetts General Hospital Dermatology Laser Center, Harvard Medical School, Boston, USA.
BACKGROUND: Laser irradiation of congenital melanocytic nevi is a
controversial treatment. Recurrence of lesions after laser treatment
appears to be the rule, and the effects of laser irradiation on cellular
biological behavior and the possible mutagenic responses of nevomelanocytes
that have received nonlethal doses of irradiation are still unclear.
Without treatment, there is an increased potential for malignant
degeneration over a life-time. The purpose of this study was to examine the
effects of Q-switched lasers on congenital nevi and to explain the
mechanism(s) behind the response of the nevi to laser treatment. Five
congenital nevi were divided into 3 equal parts: 1 part was treated with
the Q-switched ruby laser at a wavelength of 694 nm, 1 part was treated
with the Q-switched neodymium: YAG laser at a wavelength of 1064 nm, and 1
part was left untreated to serve as control. At intervals ranging from 3
days to 3 months after laser irradiation, the lesions were excised and
evaluated by routine staining. This clinical study was conducted entirely
at the Massachusetts General Hospital Dermatology Laser Center, Boston,
Mass. OBSERVATIONS: Both the superficial and the deep portions of the
congenital melanocytic nevi were affected by the 2 lasers, as evidenced by
macroscopic inspection as well as microscopic evaluation. However, the
Q-switched laser treatment did not destroy all nevomelanocytes,
particularly in the deeper, less pigmented portions of the lesions.
CONCLUSIONS: Both the Q-switched ruby laser and the neodymium: YAG laser
often removed only the superficial portion of the congenital melanocytic
nevi. The Q-switched ruby laser (694 nm) appeared to be more effective in
removing nevomelanocytes than the Q-switched neodymium: YAG laser (1064
nm).
