CHGA and neoplasm: Gastro-entero-pancreatic NETs (GEP-NETs) are the most common type of tumors, and have been classified by the World Health Organization into three categories (G1, G2 and G3) based on tumor size, histopathological differentiation, proliferation index (Ki-67), hormonal behavior, neuroendocrine biomarkers (such as serotonin and chromogranin A), direct invasion, and distant metastasis [4–6].