GAST and Down syndrome: It is reported that almost all duodenal NETs present no functional syndrome despite the positive immunoreactivity for gastrin, somatostatin, and/or serotonin[25] and that only immunoreactivity for gastrin with functional syndrome could be associated with metastasis in duodenal NETs.[17] In the present study, none of the patients had functional syndrome; furthermore, none had MEN-1.