CHGA and neuroendocrine neoplasm: Because of the heterogeneity of the disease, neuroendocrine neoplasms secrete a vast spectrum of protein or hormonal markers aside from CgA and 5-HIAA, such as insulin, gastrin, glucagon, somatostatin, growth hormone, calcitonin, substance P, pancreastatin, etc (Oronsky et al., 2017).