EPILUMINESCENT LIGHT-MICROSCOPY OF MELANOCYTIC LESIONS AFTER DERMOEPIDERMAL SPLIT

Background: In vivo epiluminescent light microscopy (ELM) of pigmented skin lesions reveals numerous elementary structures, Among them, the pigment network (PN), black dots (ED) and brown globules (BG) constitu te important semiologic features. Based on histological extrapolations , it hits been postulated that PN should reflect the presence of melan in in the epidermis and its honeycomb aspect should result from the de rmoepidermal architecture, Objective: To demonstrate this directly by analysing separately by ELM the epidermal and dermal sides of melanocy tic lesions. Methods: We split the epidermis from the dermis of 10 pig mented lesions (6 lentigos, 4 nevocytic nevi) by incubation with dispa se. ELM images were done in vivo before excision. then ex vivo on the whole specimen and separately on the split epidermis and dermis, Epide rmal and dermal specimens were finally controlled by histology. Result s: PN was observed only on the epidermal side of the split. Its organi zation was remarkably conserved after the procedure as compared with p rior in vivo images, In contrast, pigmentation observed on dermal side s of the splits showed no organized pattern and corresponded to melano phages. BG were found on the dermal side and ED on the epidermal side of the split lesions, which confirms previous hypotheses. Conclusion: By subtracting the dermal pigmentation and vessels from the image, the split technique has thus established the epidermal origin of the PN a nd given a more detailed ELM analysis of network components.