Background: We conducted a nationwide survey to estimate the incidence of neuroendocrine gastrointestinal tumors (NETs) newly diagnosed in Japan from 2002 through 2004. Methods: Data on 1541 patients, 514 pancreatic endocrine tumors (PETs) and 1027 gastrointestinal carcinoids (GICs), were collected and analyzed. Results: Nonfunctioning tumors (NF-PET) constituted 47.7% of PETs. Next in frequency were insulinoma (31.7%) and gastrinoma (8.6%). Malignancy was frequent in NF-PETs (46.1%) and gastrinomas (45.5%), but only 7.4% of insulinomas were malignant. The incidence of multiple endocrine neoplasia type-1 associated with PETs was 7.4%. The incidence of GICs was 28.8%, 5.2%, and 66.0% in foregut, midgut, and hindgut, respectively. Carcinoid syndrome and metastases were observed in only 1.7% and 5.6% of GICs, respectively. Conclusions: The incidence of NETsin Japan was clarified by this preliminary study. Comparatively large differences in GICs between Japan and Western nations were present with regard to the location, symptomatic status, and prevalence of malignancy.
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