[Merkel cell tumor of the skin]

A skin tumor of a 66-year-old female was examined morphologically and immunohistochemically in relation to its histogenetic aspect. The tumor was located within the dermis and composed of compact round cells with scanty cytoplasm. Electron-microscopic study revealed the presence of dense-cored granules within the cytoplasm. Thus the tumor was thought to derive from Merkel cells. The tumor cells were positive for keratin and negative for S-100 protein by immunohistochemistry. Therefore, we posit that the tumor cells did probably not originate from the neural crest, but rather from epidermal immature cells.