Dermabrasion in acquired melanocytic nevi: a histopathological and immunohistochemical study

When subjected to trauma, acquired melanocytic nevi may present atypical histological features similar to alterations that occur after exposure to ultraviolet radiation. These persist for up to 3 weeks. To date, no study has evaluated the alterations that occur after dermabrasion in acquired melanocytic nevi.

To evaluate the histopathological and immunohistochemical alterations those occur in acquired melanocytic nevi, 4 weeks after dermabrasion.

This study evaluated 50 acquired melanocytic nevi, in which half of each lesion was submitted to dermabrasion, leaving the other half intact, and compared the histopathological and immunohistochemical findings from the 2 sides 4 weeks after the procedure.

Five acquired melanocytic nevi were from male and 45 from female patients. The age of the patients varied from 15 to 69 years. On the dermabraded side, there was a greater frequency of atypical melanocytes (P = 0.015), increase in relation to nucleus/cytoplasm of the melanocytes (P = 0.034); inflammatory infiltrate (P = 0.007); and neovascularization (P = 0.004). In the immunohistochemical evaluation, there was a significantly higher percentage of immunoreactive melanocytes on this side for the HMB-45 only in the junctional component (P = 0.001) and for Ki-67, at a low rate, in the dermis (P = 0.03).

Four weeks after the dermabrasion, atypical features, such as melanocytic atypia and pagetoid spread remained. Although these alterations may simulate melanoma in situ, the association with features of histopathological tissue repair (inflammatory infiltrate and neovascularization), together with immunohistochemical findings that are uncharacteristic of malignancy, favors a diagnosis of a benign lesion. These atypical alterations persist longer than those found after ultraviolet radiation.