[Three-dimensional structures of epidermal melanocytes in normal human skin].

To elucidate the three-dimensional distribution and cell structure of human epidermal melanocytes in vivo, normal skin specimens were analyzed by a stereographic and stereometric method using computer. After brief fixation, dihydroxyphenylalanine (DOPA)-melanosome reaction method was performed. Specimens were then post-fixed with glutaraldehyde and osmium tetroxide, dehydrated, and embedded in Epon. Serial sections were obtained in an ultramicrotome and stained with toluidine blue. Epidermal melanocytes were stained dark brown by this method. From the serial two-dimensional figures of the melanocytes, three-dimensional images of their cell structures were reconstructed using a computer-stereography ++ system (Cosmozone 2SA, Nikon, Tokyo). Stereographicaly, the epidermal melanocytes were distributed unevenly on a waving epidermal basement membrane; some of them often gathered. The melanocytes showed spherical cell bodies extending several thin processes, whereas epidermal basal keratinocytes showed ellipsoidal cell bodies. By stereometry, the melanocytes had a significantly larger cytoplasm and a smaller nucleus in volumes compared with the basal keratinocytes. Our stereological method may prove to be important in determining three-dimensional features of normal or abnormal melanocytes.