Merkel cell neoplasms

Abstract

Seven primary malignant neoplasms of the skin composed of cells with features of Merkel cells are described. Each of them developed in older individuals, resembled either a large cell lymphoma or an undifferentiated carcinoma histologically, and contained APUD cell-type dense-core granules and intercellular junctions when studied by electron microscopy. Six neoplasms were situated in the dermis, but the seventh seemed to arise from the epidermis and, in addition, had a squamous component. Three neoplasms recurred following local resection and four metastasized to regional lymph nodes. A review of published reports of similar cases supports the impression that these neoplasms have a predilection for the skin of the face. The clinical behavior of these neoplasms, the likely relationship of the cells which constitute them to Merkel cells, and the implications of their differentiation for the embryological origin of Merkel cells arc discussed.