title: Epidemiological study of gastroenteropancreatic neuroendocrine  tumors in Japan.
abstract: BACKGROUND
  There have been few epidemiological studies on gastroenteropancreatic neuroendocrine tumors (GEP-NETs) in Japan.
  
  
  METHODS
  We examined the epidemiology of GEP-NETs [pancreatic endocrine tumors (PETs) and gastrointestinal neuroendocrine tumors (GI-NETs)] in Japan in 2005 using a nationwide stratified random sampling method.
  
  
  RESULTS
  A total of 2,845 individuals received treatment for PETs. Prevalence was estimated as 2.23/100,000 with an annual onset incidence of 1.01/100,000. Non-functioning tumor (NF)-PET constituted 47.4%, followed by insulinoma (38.2%) and gastrinoma (7.9%). Distant metastases were reported in 21% patients with NF-PETs and occurred more frequently as tumor size increased (>2 cm). Multiple endocrine neoplasia type 1 (MEN-1) was detected in 10% of PETs but only in 6.1% of NF-PETs. NF-PETs were detected incidentally by physical examination in 24% patients. In 2005, an estimated 4,406 patients received treatment for GI-NETs. Prevalence was estimated as 3.45/100,000, with an annual onset incidence of 2.10/100,000. The locations of GI-NETs varied: foregut, 30.4%; midgut, 9.6%; and hindgut, 60.0%. Distant metastases were observed in 6%. Lymph node metastases occurred more frequently as tumor size increased (>1 cm). The frequency of MEN-1 complications was 1%. Physical examination revealed GI-NETs in 44% patients. The frequency of symptomatic GI-NETs was 3.4%. Interestingly, 77.1% of patients with foregut GI-NETs had type A gastritis.
  
  
  CONCLUSIONS
  Our results show there are large differences in GEP-NETs between Japan and Western nations, primarily due to differences in the presence of MEN-1 in NF-PETs and the location, symptomatic status, and prevalence of malignancy in GI-NETs.
authors.affiliation: Department of Medicine and Bioregulatory Science, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
authors.forename: Tetsuhide
authors.initials: T
authors.lastname: Ito
authors.forename: Hironobu
authors.initials: H
authors.lastname: Sasano
authors.forename: Masao
authors.initials: M
authors.lastname: Tanaka
authors.forename: R Yoshiyuki
authors.initials: RY
authors.lastname: Osamura
authors.forename: Iwao
authors.initials: I
authors.lastname: Sasaki
authors.forename: Wataru
authors.initials: W
authors.lastname: Kimura
authors.forename: Koji
authors.initials: K
authors.lastname: Takano
authors.forename: Takao
authors.initials: T
authors.lastname: Obara
authors.forename: Miyuki
authors.initials: M
authors.lastname: Ishibashi
authors.forename: Kazuwa
authors.initials: K
authors.lastname: Nakao
authors.forename: Ryuichiro
authors.initials: R
authors.lastname: Doi
authors.forename: Akira
authors.initials: A
authors.lastname: Shimatsu
authors.forename: Toshirou
authors.initials: T
authors.lastname: Nishida
authors.forename: Izumi
authors.initials: I
authors.lastname: Komoto
authors.forename: Yukio
authors.initials: Y
authors.lastname: Hirata
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Nakamura
authors.forename: Hisato
authors.initials: H
authors.lastname: Igarashi
authors.forename: Robert T
authors.initials: RT
authors.lastname: Jensen
authors.forename: Bertram
authors.initials: B
authors.lastname: Wiedenmann
authors.forename: Masayuki
authors.initials: M
authors.lastname: Imamura
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D003625:Data Collection; D005260:Female; D005770:Gastrointestinal Neoplasms / Q000453:epidemiology* / Q000473:pathology; D006801:Humans; D015994:Incidence; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D018358:Neuroendocrine Tumors / Q000453:epidemiology* / Q000473:pathology; D010190:Pancreatic Neoplasms / Q000453:epidemiology* / Q000473:pathology; D015995:Prevalence; D055815:Young Adult