J.Jpn. Surg. Soc.. 99(6): 336-344, 1998

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Feature topic

MOLECULAR BIOLOGICAL BACKGROUND OF FAP AND HNPCC, AND TREATMENT STRATEGIES OF BOTH DISEASES DEPEND UPON GENETIC INFORMATION

Recent advancement of molecular biology disclose responsible genes of FAP (familial adenomatous polyposis) and HNPCC (hereditary non polyposis colorectal cancer), Gardner Syndrome is now categorized as subtype of FAP. Turcot Syndrome is now known as a heterogeneous disease. Turcot Syndrome caused by APC gene develops medulloblastoma and Turcot Syndrome caused by mismatch repair gene develops glioblastoma. Because of the discovery of APC gene, the presymptomatic diagnosis of asymptomatic gene carriers are now available and preventive surgery can be planned.
FAP patients with mutated APC gene between codon 1250 and 1464 shows severe phenotype. It is known that FAP patient whose APC gene mutation locates at codon 1309 develops cancer 10 years earlier in comparison to the rest of the cases. Consequstly risky rectal mucosa should be removed in this group of patients.
As for HNPCC, presymptomatic diagnosis is still not possible because the penetrance rate has not been estimated yet and some additional responsible genes are expected to be discovered. Replication error, mutator phenotype of mismatch repair gene is useful indicator to predict second primary cancers. When the patient in a HNPCC family develops adenoma with microsatellite mistability, preventive colectomy might be one of the surgical option with the informed consent of the patient.

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