AFP and cancer: The cancer cells were also positive for cytokeratin-7 (CK7; Fig. 6a), CK19 (Fig. 6b), and CA19-9 (Fig. 6c) but negative for CK20 (Fig. 6d), alpha-fetoprotein (AFP; Fig. 6e), and carcinoembryonic antigen (CEA, Fig. 6f).