Cancer genetics and breast cancer.

The risk of developing breast cancer is multifactorial and, at times, modifiable. However, the risk imposed by family history and hereditary pathogenic variants in a person's genetic code is, at present, an important fixed variable. Therefore, it is imperative to identify patients at risk for hereditary breast cancer and to understand the current evidence-based approach to the management of that risk. This chapter focuses on how genes play a role in breast cancer risk, why certain genes are commonly involved in hereditary breast cancer, and what are the specific genes and genetic syndromes that put patients at risk for breast cancer. Hereditary cancer susceptibility syndromes, including Hereditary Breast and Ovarian Cancer Syndrome (HBOC - BRCA1/2), Cowden Syndrome (CS - PTEN), Li-Fraumeni Syndrome (LFS - TP53), Peutz-Jegher Syndrome (PJS - STK11), Neurofibromatosis Type 1 (NF1), and Diffuse Hereditary Gastric Cancer Syndrome (CDH1) will be discussed along with individual genes not associated with a particular syndrome (ATM, BARD1, CHEK2, and PALB2).