Treatment of benign and atypical nevi with the normal-mode ruby laser and the Q-switched ruby laser: clinical improvement but failure to completely eliminate nevomelanocytes.

OBJECTIVE: To evaluate the effect of normal-mode and Q-switched ruby laser light (694 nm) on nevomelanocytes of benign, atypical, and congenital nevi.

DESIGN: Half of the lesion of each of 31 nevi was treated with either the Q-switched ruby laser or the normal-mode ruby laser or both; the other half of the lesion was covered with aluminum foil and was not treated.

SETTING: A university-affiliated, hospital-based laser center.

PATIENTS: Sixteen patients with a total of 31 melanocytic nevi were enrolled in the study.

INTERVENTIONS: All nevi were evaluated by at least 2 dermatologists to assess the degree of clinical atypia. Photographs were taken before and immediately after treatment and at each follow-up visit. The digital imaging system was used to evaluate the number of melanocytes in a measured length of basement membrane zone.

MAIN OUTCOME MEASURE: Three individual readings (number of melanocytes per unit length) were taken on both the control and treated halves and then compared to quantitate treatment effect. All analyses used averages from 3 measurements. A Student paired t test was used to compare the treated and untreated sides.

RESULTS: Sixteen (52%) of the nevi showed a clinically visible decrease in pigment on the treatment side at the 4-week follow-up visit.

CONCLUSION: No lesions had complete histologic removal of all nevomelanocytes. Therefore, 1 or 2 laser treatments are not sufficient to cause complete removal of a lesion either clinically or histologically.