Breast Cancer

Breast cancer is the most common cancer and the second most common cause of cancer-related death after lung cancer in females in both developed and developing world accounting for 25% of all female cancers and 12% of all cancer cases. Breast cancer mortality rates have been decreasing due to early detection and improvements in adjuvant treatment. Increasing age and female sex are the most important breast cancer risk factors along with family history, radiation exposure, nulliparity, younger age at menarche, delayed pregnancy, hormone replacement therapy, and single-gene germline mutations of BRCA1 or BRCA2 gene, while younger age at menopause and prolonged breastfeeding decrease the risk of breast cancer. Prognosis is dependent on the size of the tumor, lymph node status, and biology of cancer. TNM staging classification includes tumor grade, human epidermal growth factor-2 receptor, estrogen receptor, progesterone receptor, and genomic assays. Basic concepts that are crucial to understanding breast cancer are reviewed in depth in this chapter.