AVP and neoplasm: Immunohistochemistry showed positivity for CgA, Syn, CD56, CK, somatostatin receptors 2 (SSTR2, Fig. 4A), and vasopressin (NB110-65214, Neurophysin II/Arg-vasopressin Antibody, Novus Biologicals, Fig. 4B) in the tumor cells, indicating a vasopressin-producing pNET.