Fluorescence-microscopic investigations of pigment cells of lentigo maligna (melanosis circumscripta praeblastomatosa Dubreuilh) and lentigo maligna melanoma.

With fluorescence-histochemical methods (formalin-induced fluorescence), the different stadia of development of lentigo maligna (Morbus Dubreuih) and lentigo maligna melanoma were investigated. In this way, the special stadia can be clearly characterized using the fluorescence-microscope. In the earliest stadium of malignancy, only the pigment-cells of the basal part of the epidermis seem to be numerous. At this time, these cells are mainly arranged as palisades in the basal layer, and their strongest dendrites are usually directed towards the corneal layer. As the malignancy progresses, the pigment-cells are arranged in several layers in the basal epidermis. In this case, polymorphism of the cells is obvious and their dendrites spread in all directions. A further stadium shows pathological alterations resembling a lentigo with long rete ridges. The atypical cells cluster together into the so-called pseudonests, predominantly at the tips of these rete ridges. With the fluorescence-microscope, dendrites are seldom visible here. In the stadium of tumorous growth, all above-described alterations of the epidermis in lentigo maligna are no longer detectable. Malignant cells in the dermis, which form as a tumor mode, seldom show dendrites. These cells are mainly round or oval-shaped; at best there are some spindle cells in certain areas of the tumor. The epidermis covering the tumor node is infiltrated by some tumor cells but the characteristic alterations as described above for the various stadia of lentigo maligna are no longer visible. Even fluorescence-microscopically, a tumor node of lentigo maligna does not seem to be different from a primary nodular melanoma or a tumor node of a superficial spreading melanoma, if the flat parts of the tumors are not considered in the diagnosis.