SYP and adenocarcinoma: A panel of 3 IHC staining markers, chromogranin, synaptophysin, and CD56, is used to support the diagnosis of NEC and distinguish it from adenocarcinoma.[36] Uccella et al suggested a combined expression of chromogranin and synaptophysin was adequate to confirm neuroendocrine differentiation.[9] Although it is not a neuroendocrine marker, Ki-67 is crucial for the proliferative activity assessment and distinction of NECs from NETs.