title: Singapore familial adenomatous polyposis (FAP) patients with classical adenomatous polyposis but undetectable APC mutations have accelerated cancer progression.
abstract: OBJECTIVE
  Germline mutation in adenomatous polyposis coli (APC) is detected in up to 80% of familial adenomatous polyposis (FAP) patients worldwide. In this study, we evaluated clinical features and APC mutations of Singapore FAP patients and contrasted genotype-phenotype correlation with Caucasians from other regions of the world and between FAP patients with and without detectable APC mutations.
  
  
  METHODS
  We screened 242 members from 57 unrelated FAP families using a combination of cDNA protein truncation test, multiplex ligation-dependent probe amplification, and differential expression techniques.
  
  
  RESULTS
  APC germline mutations were detected in 50 families. In contrast to Caucasians, fundic gland polyposis in Singapore patients was associated with APC mutations throughout the coding region and osteomas were also not confined to codon 767-1573. There was also no FAP-associated hepatoblastoma or medullablastoma. APC mutation-negative patients from four families with mixed (adenomatous/hyperplastic/atypical juvenile) polyps were subsequently reclassified as hereditary mixed polyposis syndrome (HMPS) patients. APC mutation-negative patients with classical adenomatous polyposis were negative for MYH, beta-catenin, and Axin 1 mutations. These patients had a significantly older age at diagnosis (P < 0.001) and more colorectal cancers (P= 0.017) than patients with APC mutations.
  
  
  CONCLUSIONS
  We achieved a 94% (50/53) APC mutation detection rate via a combination of techniques, suggesting that the current detection rate is probably not exhaustive. Singapore patients have some features similar to and other features distinct from Caucasians. Furthermore, APC mutation-negative patients have accelerated cancer progression that merits closer surveillance.
authors.affiliation: Department of Colorectal Surgery, Singapore General Hospital, Singapore.
authors.forename: Xia
authors.initials: X
authors.lastname: Cao
authors.forename: Yi
authors.initials: Y
authors.lastname: Hong
authors.forename: Kong Weng
authors.initials: KW
authors.lastname: Eu
authors.forename: Carol
authors.initials: C
authors.lastname: Loi
authors.forename: Peh Yean
authors.initials: PY
authors.lastname: Cheah
mesh_terms: D011125:Adenomatous Polyposis Coli / Q000208:ethnology* / Q000235:genetics* / Q000473:pathology; D000328:Adult; D000368:Aged; D044466:Asian People / Q000235:genetics*; D015179:Colorectal Neoplasms / Q000208:ethnology / Q000235:genetics / Q000473:pathology*; D005260:Female; D017491:Genes, APC; D005838:Genotype; D018095:Germ-Line Mutation / Q000235:genetics*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010641:Phenotype; D012846:Singapore