“…Primary choroid plexus tumors are typically positive for CK7, a type of cytokeratin, and negative for CD20, which differentiates them from metastatic tumors. 31 Excitatory amino acid transporter 1 is believed to stain CP tumors but not metastatic carcinomas. Conversely, human epithelial antigen (HEA)-125 and Ber-EP4 clones, two types of monoclonal antibodies, are stained in metastatic carcinomas but not in CP tumors.…”