When vitiligo occurred on lesions of the pigmented nevus, the behavior of pigment cells in this nevus was investigated. Three cases of giant hairy nevi, seven cases of moles, three cases of Mongolian spots and eleven specimens in nine cases of halo nevi were used. Giant hairy nevi combining with vitiligo showed intensive decreases in nevus cells, particularly superficial A and Btype nevus cells. The epidermal dopa-positive melanocytes and melanin granules in the epidermis decreased, but still remained. On the other hand, moles in vitiligo showed an almost complete disappearance of epidermal dopa-positive melanocytes and melanin granules in the epidermis; nevus cells in the dermis decreased only slightly. Mongolian spots with vitiligo showed an epidermis similar to vitiligo, but the dermal melanocytes were hardly changed. Halo nevi exhibited an intensive decrease and degeneration of nevus cells and marked lymphocytic infiltration. Some of them showed disappearance of epidermal dopa-positive melanocytes and melanin granules in the epidermis.The characteristic findings of vitiliginous skin are mostly restricted to epidermis. In contrast, however, it is interesting to note that, on the lesions of nevocellular nevi with vitiligo, the dermis also exhibited some decrease and degeneration of nevus cells and lymphocytic infiltration.

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