[Results of a nationwide survey of gastrointestinal tumors in Japan].

We conducted a nationwide survey to estimate the incidence of neuroendocrine gastrointestinal tumors (NETs) newly diagnosed in Japan from 2002 through 2004. Five hundred and fourteen pancreatic endocrine tumors (PETs) and 1,027 gastrointestinal carcinoids (GICs) were recorded and analyzed. 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 the foregut, midgut, and hindgut, respectively. Carcinoid syndrome and metastases were observed in only 1.7% and 5.6% of GICs, respectively. The incidence of NETs in 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. At present, the results of an epidemiologic investigation in 2005 in Japan are being analyzed, and the outcome of the survey in 2005 will be clarified in the very near future.