Genetics of Breast Cancer

Abstract
Breast cancer, like other types of cancer, is a complex condition. Many factors, such as smoking, radiation and pesticide exposure, early age at menarche (first menstrual period) and late age at menopause have been implicated in the development of breast cancer. The individual predisposition to developing breast cancer is often determined genetically: a person may inherit a mutated gene, or develop a new mutation. Some breast cancers result from the familial cancer syndromes. Such syndromes are caused by mutations in multiple genes and can be inherited in either autosomal recessive or autosomal dominant fashion. Cancer syndromes, such as Cowden syndrome* or Bloom syndrome** lead to development of multiple cancers at early age. However, these syndromes are quite rare and constitute less than 1% of all breast cancer incidences. The more commonly mutated genes, which are found in 5-10% of all breast cancers, are BRCA-1 and BRCA-2 (BReast CAncer). These genes are inherited in autosomal dominant pattern and express high penetrance. The mutated versions of BRCA-1 and BRCA-2 are found in breast cancers, as well as in ovarian cancers. There is evidence that, apart from BRCA-1 and BRCA-2 genes, more of the breast cancer-related genes exist. Currently, research is on the way to identify them and develop screening techniques.

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• Ways to estimate a woman's probability of carrying breast cancer genes:
• Role of personal history of cancer/ breast cancer
• Role of family history of cancer/breast cancer
• Further management of the patients with identified breast cancer gene