title: Macroscopic morphology for estimation of malignant potential in pancreatic neuroendocrine neoplasm.
abstract: OBJECTIVE
  Pancreatic neuroendocrine neoplasm (Pan-NEN) representing approximately 1.3 % of pancreatic malignancy cases in incidence has been a so rare disease that it remains major problem to analyze the malignant potential. The aim of this study was to verify whether the macroscopic morphology of Pan-NEN, a novel pathological classification, contributes to malignant potential.
  
  
  METHODS
  From a total of 86 patients with Pan-NEN, 41 surgical sections obtained from the primary site were classified by their morphology into a simple nodular (SN) group and a non-SN group. The non-SN group was further divided into three subtypes: simple nodular with extranodular growth (SNEG), confluent multinodular (CM), and infiltrative (IF). The clinicopathological features of the SN and the non-SN groups were retrospectively compared.
  
  
  RESULTS
  Overall 5-year survival rates with and without surgical resection were 94 and 48 %, respectively. SN and non-SN types were identified in 21 and 20 patients, respectively. The non-SN group comprised 14 SNEG type, 2 CM type, and 4 IF type. Synchronous lymph node metastases (p = 0.009), synchronous liver metastases (p = 0.048), microinvasion to an adjacent organ (p < 0.001), vascular invasion (p = 0.023), and neural invasion (p = 0.019) were more significant in the non-SN group than in the SN group. As judged by WHO 2004 classification and TNM stages (AJCC and ENETS), non-SN type showed malignant trend (p < 0.05). Moreover, overall 5-year survival rates of SN and non-SN groups were 100 and 84.4 %, respectively (p = 0.048).
  
  
  CONCLUSIONS
  Non-SN tumors may have higher malignant potential than SN tumors.
authors.affiliation: Department of Hepato-Biliary-Pancreatic Surgery, Graduate School of Medicine, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8519, Japan.
authors.forename: Eriko
authors.initials: E
authors.lastname: Katsuta
authors.affiliation: Department of Hepato-Biliary-Pancreatic Surgery, Graduate School of Medicine, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8519, Japan. kudomsrg@tmd.ac.jp.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kudo
authors.affiliation: Department of Human Pathology, Graduate School of Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Takumi
authors.initials: T
authors.lastname: Akashi
authors.affiliation: Department of Hepato-Biliary-Pancreatic Surgery, Graduate School of Medicine, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8519, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Mitsunori
authors.affiliation: Department of Hepato-Biliary-Pancreatic Surgery, Graduate School of Medicine, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8519, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Matsumura
authors.affiliation: Department of Hepato-Biliary-Pancreatic Surgery, Graduate School of Medicine, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8519, Japan.
authors.forename: Arihiro
authors.initials: A
authors.lastname: Aihara
authors.affiliation: Department of Hepato-Biliary-Pancreatic Surgery, Graduate School of Medicine, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8519, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Ban
authors.affiliation: Department of Hepato-Biliary-Pancreatic Surgery, Graduate School of Medicine, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8519, Japan.
authors.forename: Takanori
authors.initials: T
authors.lastname: Ochiai
authors.affiliation: Department of Molecular Oncology, Graduate School of Medicine, Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Shinji
authors.initials: S
authors.lastname: Tanaka
authors.affiliation: Department of Human Pathology, Graduate School of Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Eishi
authors.affiliation: Department of Hepato-Biliary-Pancreatic Surgery, Graduate School of Medicine, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8519, Japan.
authors.forename: Minoru
authors.initials: M
authors.lastname: Tanabe
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018358:Neuroendocrine Tumors / Q000473:pathology*; D010190:Pancreatic Neoplasms / Q000473:pathology*
keywords: Clinicopathological features; Morphology; Pancreatic neuroendocrine tumor; Postoperative outcome