title: Undifferentiated histology after endoscopic resection may predict synchronous and metachronous occurrence of early gastric cancer.
abstract: BACKGROUND
  Endoscopic resection (endoscopic mucosal resection, EMR, and endoscopic submucosal dissection, ESD) has been accepted worldwide as a less invasive standard treatment for early gastric cancer (EGC). However, the risk of synchronous and metachronous gastric cancer developing in the post-endoscopic resection patient has become a major problem. We investigated the incidence and characteristics of synchronous and metachronous multiple gastric cancers in a retrospective study of patients with EGC after endoscopic resection.
  
  
  METHODS
  We studied the clinicopathological features of 235 patients with EGC who had undergone endoscopic resection and were periodically followed up using endoscopic examinations (181 with a single lesion, 34 synchronous multiple lesions, and 20 metachronous multiple lesions).
  
  
  RESULTS
  The overall incidence of synchronous and metachronous multiple gastric cancer was 14.5 and 8.5%, respectively, during a follow-up of 12-77 (median 26.5) months. Undifferentiated histology of the primary lesion was related to the occurrence of synchronous gastric cancer (p < 0.001). Undifferentiated histology and upper location of the primary lesion were correlated with the occurrence of metachronous gastric cancer (p = 0.002, 0.001). Most synchronous and metachronous lesions were well to moderately differentiated (82.4 and 80.0%); however, the proportion with undifferentiated histology (including poorly differentiated carcinoma and signet ring cell carcinoma) in synchronous and metachronous gastric cancer was significantly higher than in single gastric cancer (p = 0.008).
  
  
  CONCLUSIONS
  Undifferentiated histology of EGC may predict the occurrence of synchronous and metachronous lesions after endoscopic resection.
authors.affiliation: Department of Internal Medicine, Yonsei Institute of Gastroenterology, Yonsei University College of Medicine, Seodaemun-gu, Seoul, Korea.
authors.forename: Ju Hee
authors.initials: JH
authors.lastname: Seo
authors.forename: Jun Chul
authors.initials: JC
authors.lastname: Park
authors.forename: Yu Jin
authors.initials: YJ
authors.lastname: Kim
authors.forename: Sung Kwan
authors.initials: SK
authors.lastname: Shin
authors.forename: Yong Chan
authors.initials: YC
authors.lastname: Lee
authors.forename: Sang Kil
authors.initials: SK
authors.lastname: Lee
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018279:Carcinoma, Signet Ring Cell / Q000453:epidemiology / Q000473:pathology; D055088:Early Detection of Cancer; D005260:Female; D005500:Follow-Up Studies; D005773:Gastroscopy; D016481:Helicobacter Infections / Q000150:complications; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000453:epidemiology / Q000473:pathology; D016609:Neoplasms, Second Primary / Q000453:epidemiology / Q000473:pathology; D011184:Postoperative Period; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D013274:Stomach Neoplasms / Q000453:epidemiology / Q000382:microbiology / Q000473:pathology* / Q000601:surgery*; D013997:Time Factors