INS and neuroendocrine neoplasm: Neuroendocrine tumors (NETs) originate from neuroendocrine cells, which receive neural input and play a key role in transmitting signals by secreting bioactive substances such as monoamines (e.g., serotonin), peptides (e.g., somatostatin), and hormones (e.g., insulin) that regulate a wide range of physiological functions.