MUC1 and head and neck squamous cell carcinoma: Whether HPV-related HNSCC viral antigens (e.g., E6/E7) represent a potential target for vaccination, for HPV-negative HNSCCs tumor associated-antigens (TAA) such as for example mucin 1 (MUC1), carcinoembryonic antigen (CEA), and melanoma-associated antigen-A3 (MAGEA3, unmutated antigens) should be considered [56–59].