A 66-year-old male with Merkel cell carcinoma is reported. A red nodule was noticed on his right temporal region about a year before visiting our clinic. The nodule was excised by a practicing doctor and was histopathologically diagnosed as basal cell carcinoma. When he visited to our clinic, the metastatic tumors were seen on his scalp and trunk, and were found in the mediastinal, axillary and abdominal lymph nodes, and in the brain by computed tomography. We histopathologically examined the tumor from the primary lesion, and the metastatic tumor on his back. Light microscopy of the primary lesion revealed that nests of tumor cells localized in the upper and middle dermis. Tumor cells had round nuclei and poor cytoplasm. Mitosis was seen in many tumor cells. Immunocytochemically, tumor cells were positively stained with anti-neuron-specific enolase antibody and anti-cytokeratin20 antibody. Electron microscopically, the intermediate filaments were observed around the nuclei. Desmosome-like dense materials were seen in the intercellular spaces of tumor cells. No dense core granules with a halo were found. Some tumor cells appeared apoptotic. The tumors responded to treatment with cisplatin/etoposide.
