Merkel cell tumor coexpressing cytokeratin and neurofilament proteins

Whorled filaments 10 nm in width were identified by anti-intermediate filaments antibodies in a Merkel cell tumor from a 52-year-old man. Immunohistochemical tests revealed that the tumor was stained with anti-keratin antibody and antibodies against the 68-kd and 200-kd subunits of neurofilament proteins but not antibody against the 150-kd subunit. This is the first reported case of Merkel cell tumor expressing a 200-kd subunit of neurofilament proteins.