CGA and neoplasm: In summary, the sensitivity of CgA as a tumor marker in neuroendocine tumors of the GEP system depends on the threshold cut-off level [15,16,27,28], on the specific assay for serum or plasma CgA determination [14,15,16], on NET primary location [17,18] and on the spread of disease, especially the presence of liver metastases [5,16,19,20].