SYP and neuroendocrine neoplasm: However, the utility of traditional neuroendocrine markers (synaptophysin, chromogranin, and CD56) can be limited due to their wide range of sensitivities (individual or combined, 50–80%) and expression in tumor types other than neuroendocrine neoplasms, as well as the uncertain fidelity of cytoplasmic staining (i.e., weak and/or focal reactivity) [12].