Pasternak et al investigated the expression of 5 immunohistochemical markers (CK20, NF, chromogranin, TTF−1, and CK7) and reported no significant differences between the 2 MCPyV-negative subsets.[8] Carter et al demonstrated that pure and combined MCPyV-negative MCC had similar mutational profiles, harboring deletions and/or mutations in RB1. This evidence concerns the gene TTF1 and Merkel cell skin cancer.