title: Prevalence and characteristics of nonpolypoid colorectal neoplasm in an asymptomatic and average-risk Chinese population.
abstract: OBJECTIVE
  Evidence from Japanese studies suggests that nonpolypoid colorectal neoplasia (NP-CRN) tends to be more pathologically advanced than polypoid neoplasia. However, data are limited regarding the prevalence of NP-CRN in an average-risk population. In addition, the diagnostic yield of the fecal occult blood test (FOBT) in relation to different types of colorectal neoplasms remains unclear. We prospectively investigated the prevalence and characteristics of polypoid and nonpolypoid colorectal lesions in an asymptomatic and average-risk Chinese population.
  
  
  METHODS
  The study included 12,731 asymptomatic Chinese subjects (8372 of whom were average-risk subjects) who underwent screening colonoscopy. The prevalence, histopathologic findings, and topographic distribution of polypoid and nonpolypoid colorectal lesions were determined and analyzed. The diagnostic yield of FOBT, in relation to lesion morphology, also was assessed.
  
  
  RESULTS
  NP-CRN was detected in 552 (4.3%) asymptomatic and 348 (4.2%) average-risk subjects. The prevalence of depressed NP-CRN was 0.18% in both asymptomatic and average-risk subjects. A higher proportion of smaller-sized but high-grade dysplasia and invasive carcinoma beyond the submucosal layer was noted for depressed NP-CRN compared with flat NP-CRN or polypoid neoplasia. The diagnostic yield of FOBT was comparable in depressed lesions and their polypoid counterparts.
  
  
  CONCLUSIONS
  The prevalence of NP-CRN is substantial in both asymptomatic and average-risk Chinese individuals. Some subcategories of NP-CRN in this population tend to have more advanced pathologic characteristics. These findings may lead to modification of screening and prevention strategies for colorectal cancer.
authors.affiliation: Department of Internal Medicine, National Taiwan University Hospital, National Taiwan University College of Medicine, Taipei, Taiwan.
authors.forename: Han-Mo
authors.initials: HM
authors.lastname: Chiu
authors.forename: Jaw-Town
authors.initials: JT
authors.lastname: Lin
authors.forename: Chien-Chuan
authors.initials: CC
authors.lastname: Chen
authors.forename: Yi-Chia
authors.initials: YC
authors.lastname: Lee
authors.forename: Wei-Chih
authors.initials: WC
authors.lastname: Liao
authors.forename: Jin-Tung
authors.initials: JT
authors.lastname: Liang
authors.forename: Chia-Tung
authors.initials: CT
authors.lastname: Shun
authors.forename: Hsiu-Po
authors.initials: HP
authors.lastname: Wang
authors.forename: Ming-Shiang
authors.initials: MS
authors.lastname: Wu
mesh_terms: D044466:Asian People; D003113:Colonoscopy; D015179:Colorectal Neoplasms / Q000453:epidemiology* / Q000473:pathology* / Q000503:physiopathology; D005243:Feces / Q000737:chemistry; D005260:Female; D006470:Hemorrhage / Q000175:diagnosis; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D011446:Prospective Studies; D012720:Severity of Illness Index