Morphologic investigations on the dynamics of nevus development.

The regeneration of nevus cells after shave biopsy was investigated by means of fluorescence-histochemical and electron microscopic methods. A prerequisite for the regeneration of pigmented nevi seems to be the retention of their deepest part. It appears that the remaining nevus cells primarily induce proliferation of pigment-producing dendritic cells in the epidermis. These dendritic cells form nest-like conglomerations at the dermal-epidermal junction, which eventually separate from the epidermis during a process called "dropping off". The fluorescence-histochemical and electron-microscopic results lead to the conclusion that under these circumstances melanocytes are transformed into nevus cells.