title: Diagnostic performance of conventional endoscopy in the identification of submucosal invasion by early gastric cancer: the "non-extension sign" as a simple diagnostic marker.
abstract: OBJECTIVE
  The ability to differentiate between mucosal (M) or microinvasive submucosal (SM1: depth of less than 500 µm) and invasive submucosal (SM2: depth of 500 µm or more) cancer is paramount when choosing the method of treatment for early gastric cancer (EGC). The "non-extension sign" relates to a localized increase in thickness and rigidity due to massive submucosal invasion by a cancer. The present study sought to assess the ability of conventional endoscopy (CE) to correctly identify SM2 cancer using only the non-extension sign.
  
  
  METHODS
  This is a retrospective study based on a prospectively collected database. EGCs had been diagnosed according to invasion depth as M-SM1 or SM2. In terms of the endoscopic diagnostic criterion, lesions positive for the non-extension sign were classified as SM2 cancers, while those negative for the non-extension sign were classified as M-SM1 cancers. Histopathological findings were used as the gold standard.
  
  
  RESULTS
  We examined a total of 863 lesions from 704 patients, comprising 104 true-positive, 733 true-negative, 9 false-positive, and 17 false-negative lesions. This yielded a sensitivity of 92.0 % (95 % confidence interval (CI), 87.0-97.0 %), a specificity of 97.7 % (95 % CI, 96.7-98.8 %), a positive predictive value of 85.9 % (95 % CI, 79.7-92.1 %), a negative predictive value of 98.8 % (95 % CI, 98.0-99.6 %), and a diagnostic accuracy of 96.9 % (95 % CI, 95.8-98.1 %).
  
  
  CONCLUSIONS
  The non-extension sign may be useful for accurately determining the suitability of minimally invasive endoscopic treatment. Nevertheless, considering the limitations of retrospective analysis, a further prospective study is warranted to confirm the diagnostic reliability of the non-extension sign.
authors.affiliation: Department of Gastroenterology, Fukuoka University Chikushi Hospital, 1-1-1 Zokumyoin, Chikushino City, Fukuoka, 818-8502, Japan. nagahamagogo@gmail.com.
authors.forename: Takashi
authors.initials: T
authors.lastname: Nagahama
authors.affiliation: Department of Endoscopy, Fukuoka University Chikushi Hospital, Fukuoka, Japan.
authors.forename: Kenshi
authors.initials: K
authors.lastname: Yao
authors.affiliation: Department of Pathology, Fukuoka University Chikushi Hospital, Fukuoka, Japan.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Imamura
authors.affiliation: Department of Endoscopy, Fukuoka University Chikushi Hospital, Fukuoka, Japan.
authors.forename: Toshiki
authors.initials: T
authors.lastname: Kojima
authors.affiliation: Department of Gastroenterology, Fukuoka University Chikushi Hospital, 1-1-1 Zokumyoin, Chikushino City, Fukuoka, 818-8502, Japan.
authors.forename: Kensei
authors.initials: K
authors.lastname: Ohtsu
authors.affiliation: Department of Pathology, Fukuoka University Chikushi Hospital, Fukuoka, Japan.
authors.forename: Kenta
authors.initials: K
authors.lastname: Chuman
authors.affiliation: Department of Pathology, Fukuoka University Chikushi Hospital, Fukuoka, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Tanabe
authors.affiliation: Department of Gastroenterology, Fukuoka University Chikushi Hospital, 1-1-1 Zokumyoin, Chikushino City, Fukuoka, 818-8502, Japan.
authors.forename: Rino
authors.initials: R
authors.lastname: Yamaoka
authors.affiliation: Department of Pathology, Fukuoka University Chikushi Hospital, Fukuoka, Japan.
authors.forename: Akinori
authors.initials: A
authors.lastname: Iwashita
mesh_terms: D000230:Adenocarcinoma / Q000175:diagnosis* / Q000601:surgery; D000368:Aged; D055088:Early Detection of Cancer; D005260:Female; D005500:Follow-Up Studies; D005753:Gastric Mucosa / Q000473:pathology* / Q000601:surgery; D005773:Gastroscopy / Q000379:methods*; D006801:Humans; D008297:Male; D009361:Neoplasm Invasiveness; D009367:Neoplasm Staging; D011379:Prognosis; D011446:Prospective Studies; D012189:Retrospective Studies; D013274:Stomach Neoplasms / Q000175:diagnosis* / Q000601:surgery
keywords: Conventional endoscopy; Early gastric cancer; Endoscopic submucosal dissection; Non-extension sign; Submucosal invasion