Diagnostic criteria

Classical FAP is defined clinically by the finding of at least 100 colorectal adenomatous polyps {216}. Endoscopic visual

ization of diminutive polyps may require dye spray assisted endoscopy. Histo-logical confirmation requires examination of several polyps. In the context of endoscopic screening on the basis of definite family history the detection of fewer adenomas is sufficient at an early age. The same applies on the attenuated disease form (AAPC). Final diagnosis may be achieved by demonstration of a mutated APC, but the detection rate of mutations has only been between 60 and 80% of all FAP families. In patients where the clinical criteria remain doubtful and genetic diagnosis is not achieved the finding of extracolonic features of FAP (epidermoid cysts, osteomas, desmoid tumour, gastric fundic gland polyps, etc.) may give additional diagnostic support. The following diagnostic criteria have been established: (1) 100 or more colorectal adenomas or (2) germline mutation of the APC gene or (3) family history of FAP and at least one of the following: epidermoid cysts; osteomas; desmoid tumour.

Colorectal polyps

The colorectal polyps are adenomas, most often tubular, and resemble their sporadic counterparts.

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