Chromogranin A in gastric neuroendocrine tumours: an immunohistochemical and biochemical study with region-specific antibodies

The aim of the present study was to investigate ECLomas and enterochromaffin-like (ECL) cell hyperplasia in gastric human mucosa regarding the immunohistochemical expression of chromogranin A (CgA) epitopes and to measure the same CgA epitopes in plasma samples. Eight gastric biopsies from ECLomas, seven of type I and one of type III, and biopsies from one patient showing only ECL cell hyperplasia were included in the study. Our results revealed a varying expression of region-specific CgA epitopes in the ECLomas regarding both the frequency of immunoreactive cells and intensity of immunoreactivity. CgA284–301 (pancreastatin) was not revealed in any neoplasm, whereas CgA361–372 (catestatin) was expressed in all ECLomas. However, the number of immunoreactive cells to vesicular monoamino transporter 2 (VMAT 2) or the commercial monoclonal CgA (CgA250–284) antibodies were generally higher. The plasma concentrations of the region-specific CgA radioimmunoassays differed considerably, with highest concentrations of CgA1–17 and CgA116–130 epitopes and the lowest with the CgA17–37, CgA63–76, CgA238–247 and CgA441–424 epitopes. No relationship was found between tissue expression and plasma concentration of CgA epitopes. In conclusion, this study shows that VMAT 2 and the commercial CgA antibodies seem more useful for histopathological diagnosis of ECLomas than the antibodies to the other CgA regions.