CGA and metastatic neoplasm: Thus, simple and reliable CgA study may be used for an indirect, independent diagnostic and prognostic marker in GEP-NETs in three folds: first to distinguish more benign insulinomas from more aggressive non-β-cell tumors; second, to access the degree of malignancy for primary non-β-cell tumors by the CgA staining intensity; and third, increasing serum CgA levels as an indicator of growing and metastatic tumors, since elevated serum CgA levels suggest growing tumor sizes and metastatic tumors.