INSM1 and neuroendocrine neoplasm: However, the updated WHO classification discourages the use of CD56 due to its non-specificity for neuroendocrine neoplasms (NENs) and instead advocates for CgA, SYP, and insulinoma-associated protein 1 (INSM1) as novel markers of neuroendocrine differentiation in the head and neck region [12].