Cancer Risk in Families Fulfilling the Amsterdam Criteria for Lynch Syndrome.

Importance: The data describing cancer risks associated with Lynch syndrome are variable.

Objectives: To quantify the prevalence of families that fulfill the Amsterdam I or II criteria for Lynch syndrome in the Utah population and investigate the risk of colonic and extracolonic cancers in family members and their relatives.

Design, Setting, And Participants: In a population-based study, 202 families with Amsterdam I and II criteria–positive pedigrees in the Utah Population Database were identified.