Perifollicular hypopigmentation. A cause of variegate pigmentation and irregular border in melanocytic nevi.

Abstract

Clinical and histologic features of perifollicular hypopigmentation within melanocytic nevi are described. Perifollicular hypopigmentation was observed in congenital and acquired melanocytic nevi. When the area of hypopigmentation was found within the nevus, it was circular. When the hypopigmentation was located at the edge of the nevus, however, it formed a half circle that resulted in a notch in the outline of the lesion. The phenomenon occurred in nevi with terminal hairs as well as nevi with vellus hairs. In biopsy specimens from 15 melanocytic nevi, one or more of the following findings were observed around hair follicles when compared with the remainder of the nevus: decrease in the number of junctional melanocytes as nests and solitary units (n = 12), decrease in pigment within keratinocytes (n = 14), decrease in the number of melanocytes in the papillary dermis (n = 6), and decrease in the number of melanophages (n = 6). Perifollicular hypopigmentation is a cause of variegate pigmentation and irregular border in melanocytic nevi.