Aged Aged, 80 and over Antibodies, Viral/immunology Antigens, Polyomavirus Transforming/immunology/metabolism Carcinoma, Merkel Cell/diagnosis/metabolism/*virology Cell Line, Tumor DNA Mutational Analysis Female Gene Dosage Genes, Tumor Suppressor Genotype Humans Immunohistochemistry Male Merkel cell polyomavirus/genetics/immunology/*metabolism Middle Aged Molecular Diagnostic Techniques Oncogenes Polyomavirus Infections/diagnosis/metabolism/*virology Real-Time Polymerase Chain Reaction Tumor Virus Infections/diagnosis/metabolism/*virology