SYP and large cell neuroendocrine carcinoma: However, for a definitive diagnosis of cervical LCNEC, it is also necessary to demonstrate positive expression of two or more neuroendocrine-specific immunohistochemical markers, such as synaptophysin (Syn), chromogranin A (CgA), neural cell adhesion molecule (CD56), neuron-specific enolase (Nse), insulinoma-associated protein (INSM1), and vascular endothelial growth factor (VEGF) (9).