Detection of chromogranin A in human gastric adenocarcinomas using a sensitive immunohistochemical technique

Neuroendocrine cells are often disclosed in human gastric adenocarcinomas a nd may be recognised by their immunoreactivity towards chromogranin A. Howe ver, in dedifferentiated neuroendocrine tumour cells, the chromogranin A co ntent may be reduced making it difficult to detect with conventional immuno histochemical methods. We therefore used a sensitive signal amplification t echnique in order to evaluate chromogranin A immunoreactivity and thus neur oendocrine differentiation in 40 gastric adenocarcinomas. Neuroendocrine cells were visualised by means of a monoclonal chromogranin A antibody and the avidin-biotin peroxidase complex technique, without and with addition of tyramide signal amplification. Double immunohistochemistry towards chromogranin A and Ki-67 were used to disclose proliferation in th e neoplastic cells. A marked increase in the number of carcinomas containing chromogranin A-imm unoreactive neoplastic cells was noted when applying the tyramide signal am plification technique. In addition, the number of immunoreactive cells with in each tumour increased, and in some cases almost all the neoplastic cells became immunoreactive. Chromogranin A-immunoreactive tumour cells showing signs of proliferation were found in the majority of these carcinomas. In conclusion, we have disclosed widespread immunoreactivity towards chromo granin A in a proportion of gastric adenocarcinomas when enhancing the sign al with tyramide signal amplification. Neuroendocrine differentiation is th us a common finding in gastric carcinomas when using sensitive methods.