title: Risk for high-grade dysplasia or invasive carcinoma in colorectal flat adenomas in a Spanish population.
abstract: OBJECTIVE
  to determine the frequency and malignancy risk of colonic flat adenomas among patients with colorectal polyps in a Spanish population.
  
  
  METHODS
  1300 consecutive colonoscopic examinations were reviewed; 640 polyps were detected and removed endoscopically in 298 patients. Chromoendoscopy with 0.2% indigo carmine was applied to clarify the macroscopical appearance of flat lesions. The following data was collected for flat and protruding polyps: size, location (proximal or distal to splenic flexure), histology (neoplastic or non neoplastic), high grade dysplasia (HGD) and submucosal invasive carcinoma (SIC) or beyond.
  
  
  RESULTS
  490 polyps (76.6%) were adenomas and 150 (23.4%) hyperplastic; 114 (23.3%) adenomas were flat (3 flat-depressed) whereas 376 (76.7%) were protruding. The diameter of flat and protruding adenomas was 9.2 +/- 7.9. mm and 7.0 +/- 5.9 mm, respectively (p < 0.001). A proximal location was more frequent for flat (63.1%) than for protruding adenomas (48.7%) (p = 0.003). The rate of HGD or SIC was significantly higher in flat than in protruding adenomas (7.0 vs 2.6%; p < 0.04). Two of the 3 flat-depressed lesions (both <or= 10 mm in diameter) were carcinomas (T1 and T2, respectively). Flat adenomas had an increased risk for HGD or SIC (OR = 2,7; CI, 1,04-7,04; p < 0.05).
  
  
  CONCLUSIONS
  In a Spanish population, flat adenomas represent nearly one quarter of all colorectal neoplastic polyps, their most frequent location being the right colon and they bear a higher risk of malignancy than protruding adenomas, especially for the flat depressed type.
authors.affiliation: Department of Gastroenterology. University Hospital of the Canary Islands, La Laguna, Santa Cruz de Tenerife, Spain. parrablanco@hotmail.com
authors.forename: Adolfo
authors.initials: A
authors.lastname: Parra-Blanco
authors.forename: Antonio Z
authors.initials: AZ
authors.lastname: Gimeno-García
authors.forename: David
authors.initials: D
authors.lastname: Nicolás-Pérez
authors.forename: Candelaria
authors.initials: C
authors.lastname: García
authors.forename: Carlos
authors.initials: C
authors.lastname: Medina
authors.forename: Lucio
authors.initials: L
authors.lastname: Díaz-Flores
authors.forename: Begoña
authors.initials: B
authors.lastname: Grosso
authors.forename: Alejandro
authors.initials: A
authors.lastname: Jiménez
authors.forename: Enrique
authors.initials: E
authors.lastname: Quintero
mesh_terms: D000236:Adenoma / Q000473:pathology*; D002277:Carcinoma / Q000473:pathology*; D003111:Colonic Polyps / Q000473:pathology*; D003113:Colonoscopy; D015179:Colorectal Neoplasms / Q000473:pathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D012307:Risk Factors; D013030:Spain