Sun-induced freckles in children and young adults. A correlation of clinical and histopathologic features.

Sun-induced freckles are a risk factor for epidermal and melanocytic neoplasia. Whereas sun-induced freckles in children and older adults may be clinically indistinguishable, and sun-induced freckles in older adults usually consist of increased numbers of intraepidermal melanocytes, the histology of sun-induced freckles in children remains unsettled. Using L-3,4 dihydroxyphenylalanine (DOPA)-paraffin sections, the authors examined six sun-induced freckles and adjacent nonpigmented skin (ANP) in as many white male subjects, ages 10 to 23 years. Melanocyte frequency was expressed as the ratio of DOPA-reactive melanocytes to total epidermal basal unit cells. For each case, melanocyte frequencies in freckles were significantly greater than in ANP. Cellular atypia of melanocytes was noticed in four of six freckles. Reactivity of melanocytes for HMB-45 was noticed in two freckles studied, compared with no reactivity in three specimens of ANP studied. The authors conclude the sun-induced freckles in the young may consist of a hyperplasia of melanocytes (i.e., similar to solar lentigines in the elderly), sometimes with cellular atypia, and that these findings may be relevant to melanocytic neoplasia.