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  • Approximately 3–5% of colorectal cancers (CRCs) are caused by inherited gene mutations associated with hereditary nonpolyposis colorectal cancer (HNPCC) (Lynch syndrome) or adenomatous polyposis syndromes.

  • Genetic testing is clinically available for several hereditary gastrointestinal cancer syndromes and can be used to guide cancer screening recommendations.

General Considerations

The majority of cases of gastrointestinal cancer are believed to be sporadic events; however, inherited factors play a role in development of some tumors, with an estimated 5% being attributable to a single gene mutation. Hereditary gastrointestinal cancer syndromes convey a markedly increased risk for developing cancer and require specific strategies for diagnosis and management.

Identification of hereditary gastrointestinal cancer syndromes requires a thorough evaluation of patients’ personal and family history of cancer. Clinical genetic testing can be useful in confirming the diagnosis of certain hereditary cancer syndromes and guiding cancer screening for family members. Tables 23–1 and 23–2 summarize clinical characteristics and cancer screening recommendations for the hereditary gastrointestinal cancer syndromes discussed in detail in this chapter.

Table 23–1.Clinical characteristics of hereditary gastrointestinal cancer syndromes.

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