title: Gangliocytic paraganglioma: a multi-institutional retrospective study in Japan.
abstract: BACKGROUND
  Gangliocytic paraganglioma (GP) is an extremely rare benign tumor that commonly arises from the second part of the duodenum. Since GP exhibit neither prominent mitotic activity nor Ki-67 immunoreactivity, this tumor is often misdiagnosed as neuroendocrine tumor (NET) G1 (carcinoid tumor). However, patients with GP may have a better prognosis than patients with NET G1. This fact emphasizes the importance of differentiating GP from NET G1, but few studies have reported the epidemiology and histopathology of GP because of its rarity. To differentiate GP from NET G1 with ease, we conducted a multi-institutional retrospective study analyzing the morphometric and immunohistochemical features of this tumor.
  
  
  METHODS
  Since only a limited number of patients with GP could be identified in our institute, we conducted a multi-institutional retrospective study of GP in Japan, which was approved by the Ethics Committee of our medical institute. The obtained tissue sections underwent detailed morphometric and immunohistochemical analyses. Additionally, to differentiate GP from NET G1 with ease, immunohistochemical findings were compared.
  
  
  RESULTS
  In our examination of 12 cases of duodenal GP, we found that epithelioid cells of GP exhibited positive reactivity for progesterone receptor and pancreatic polypeptide, whereas tumor cells of NET G1 were completely negative reactivity for both. Additionally, although GP is considered to be an extremely rare NET, we found that four (40.0%) of the ten patients at our institute with duodenal NET G1 actually had GP.
  
  
  CONCLUSIONS
  Although GP is regarded as a rare NET, our results suggest that it accounts for a substantial percentage of duodenal NETs. Additionally, confirmation of immunoreactivity for progesterone receptor and pancreatic polypeptide can assist in differentiating GP from NET G1.
authors.affiliation: Department of Surgical Pathology, Toho University School of Medicine, 6-11-1 Omori-Nishi, Ota-ku, Tokyo, 143-8541, Japan. yoichiro0207@hotmail.com.
authors.forename: Yoichiro
authors.initials: Y
authors.lastname: Okubo
authors.affiliation: Department of Surgical Pathology, Toho University School of Medicine, 6-11-1 Omori-Nishi, Ota-ku, Tokyo, 143-8541, Japan. tetsuo.nemoto@med.toho-u.ac.jp.
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Nemoto
authors.affiliation: Department of Surgical Pathology, Toho University School of Medicine, 6-11-1 Omori-Nishi, Ota-ku, Tokyo, 143-8541, Japan. megumi.wakayama@med.toho-u.ac.jp.
authors.forename: Megumi
authors.initials: M
authors.lastname: Wakayama
authors.affiliation: Department of Surgical Pathology, Toho University School of Medicine, 6-11-1 Omori-Nishi, Ota-ku, Tokyo, 143-8541, Japan. naobumi.tochigi@med.toho-u.ac.jp.
authors.forename: Naobumi
authors.initials: N
authors.lastname: Tochigi
authors.affiliation: Department of Surgical Pathology, Toho University School of Medicine, 6-11-1 Omori-Nishi, Ota-ku, Tokyo, 143-8541, Japan. ushino@med.toho-u.ac.jp.
authors.forename: Minoru
authors.initials: M
authors.lastname: Shinozaki
authors.affiliation: Department of Surgical Pathology, Toho University School of Medicine, 6-11-1 Omori-Nishi, Ota-ku, Tokyo, 143-8541, Japan. t-ishiwatari@med.toho-u.ac.jp.
authors.forename: Takao
authors.initials: T
authors.lastname: Ishiwatari
authors.affiliation: Department of Surgical Pathology, Toho University School of Medicine, 6-11-1 Omori-Nishi, Ota-ku, Tokyo, 143-8541, Japan. kyoko.aki@med.toho-u.ac.jp.
authors.forename: Kyoko
authors.initials: K
authors.lastname: Aki
authors.affiliation: Division of General and Gastroenterological Surgery, Department of Surgery (Omori), Toho University School of Medicine, 6-11-1 Omori-Nishi, Ota-ku, Tokyo, 143-8541, Japan. tucchie@nifty.com.
authors.forename: Masaru
authors.initials: M
authors.lastname: Tsuchiya
authors.affiliation: Department of Pathology and Oncology, University of the Ryukyus, 59, Nishihara-cho, Nakagami-gun, Okinawa, 903-0214, Japan. h014169@med.u-ryukyu.ac.jp.
authors.forename: Hajime
authors.initials: H
authors.lastname: Aoyama
authors.affiliation: Department of Pathology, Japanese Red Cross Kyoto Daini Hospital, 355-5, Jokyo-ku, Kyoto, 602-8026, Japan. katsurak@kyoto2.jrc.or.jp.
authors.forename: Kanade
authors.initials: K
authors.lastname: Katsura
authors.affiliation: Department of Pathology, Toranomon Hospital, 2-2-2 Toranomon, Minato-ku, Tokyo, 105-8470, Japan. tkshfj@gmail.com.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Fujii
authors.affiliation: Department of Pathology, Steel Memorial Hirohata Hospital, 3-1, Himeji, Hyogo, 671-1122, Japan. t_nishigami@hirohata-hp.or.jp.
authors.forename: Takashi
authors.initials: T
authors.lastname: Nishigami
authors.affiliation: Department of Pathology, Kanagawa Cancer Center, 1-1-2, Nakao, Asahi-ku, Yokohama, Kanagawa, 245-0815, Japan. yokose-t@kcch.jp.
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Yokose
authors.affiliation: Department of Pathology, Kyorin University School of Medicine, 6-20-2, Shinkawa, Mitaka, 181-8611, Japan. ohkura@ks.kyorin-u.ac.jp.
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Ohkura
authors.affiliation: Department of Surgical Pathology, Toho University School of Medicine, 6-11-1 Omori-Nishi, Ota-ku, Tokyo, 143-8541, Japan. kaz@med.toho-u.ac.jp.|Department of Dermatology, Peking University First Hospital, Beijing, China. kaz@med.toho-u.ac.jp.
authors.forename: Kazutoshi
authors.initials: K
authors.lastname: Shibuya
mesh_terms: D000368:Aged; D014408:Biomarkers, Tumor / Q000235:genetics; D002276:Carcinoid Tumor / Q000175:diagnosis* / Q000235:genetics / Q000473:pathology; D003937:Diagnosis, Differential; D004386:Duodenum / Q000473:pathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018358:Neuroendocrine Tumors / Q000175:diagnosis* / Q000235:genetics / Q000473:pathology; D010191:Pancreatic Polypeptide / Q000235:genetics; D010235:Paraganglioma / Q000175:diagnosis* / Q000235:genetics / Q000473:pathology; D011980:Receptors, Progesterone / Q000235:genetics / Q000378:metabolism
chemical_list: D014408:Biomarkers, Tumor; D011980:Receptors, Progesterone; D010191:Pancreatic Polypeptide