A reinvestigation of solar lentigines.

Solar lentigines were reinvestigated by a number of different methods to gain a better perspective on their structure. In histologic sections and dopa preparations of split skin, large numbers of melanocytes were seen crowded at the base of the clubbed, budding rete ridges. In split-skin preparations, the scanning electron microscope showed complex systems of ridges, columns, and craters on the underside of the lentiginous epidermis. Oval bodies measuring 15 to 30 mu, with dendrites, were numerous at the apices of the complex epidermal ridges; these bodies were presumed to be melanocytes. In transmission electron micrographs of lentigines, the melanosome complexes inside the keratinocytes were much larger than those found in noninvolved skin. The complex and distinctive architecture of these maculae is probably the result of concurrent proliferation of melanocytes and keratinocytes.