SYP and neuroendocrine neoplasm: Insulinoma-associated protein 1 (INSM1) has been considered as a novel immunostaining marker for neuroendocrine tumors (NETs) and is hypothesized to be more reliable than first-generation NET biomarkers, such as CGA (chromogranin A), SYP (synaptophysin), and CD56 (neural cell adhesion molecule).