Continuing Medical Education

Cancer genetics: An approach to suspected hereditary breast or colorectal cancer

C J Scott, M Schoeman, M F Urban

Abstract


Two of the most common cancers are breast cancer and colorectal cancer. Up to 10% of cases of each are associated with a high risk of recurrence in an affected individual, or of occurrence in biological relatives. This results from the presence of an underlying mutation (or ‘pathogenic variant’) in a high-penetrance gene. Such cases are typically associated with an autosomal dominant pattern of inheritance, although this may not be obvious in the family history. Genetic testing can identify many (but not all) of these cases, and should be offered to those whose family history or clinical features suggest a high risk. Although testing for certain risk genes (e.g. BRCA1 or BRCA2) has been available for years, the advent of next-generation sequencing ‘gene panels’ now allows for simultaneous testing of many more genes at lower cost. This allows for more frequent detection of pathogenic variants in underlying genes than in the past, but also makes interpretation more complex. An index of suspicion for genetic cancers and appropriate referral to a genetics health professional are increasingly important.


Authors' affiliations

C J Scott, Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, and Clinical Unit of Medical Genetics and Genetic Counselling, Tygerberg Hospital, Cape Town, South Africa

M Schoeman, Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, and Clinical Unit of Medical Genetics and Genetic Counselling, Tygerberg Hospital, Cape Town, South Africa

M F Urban, Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, and Clinical Unit of Medical Genetics and Genetic Counselling, Tygerberg Hospital, Cape Town, South Africa

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Keywords

Cancer genetics; Hereditary; Breast cancer; Colorectal cancer

Cite this article

South African Medical Journal 2019;109(4):214-218. DOI:10.7196/SAMJ.2019.v109i4.13992

Article History

Date submitted: 2019-03-29
Date published: 2019-03-29

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