Breast Surgery Notes Basics Almost all are adenocarcinomas. Based on expression of estrogen receptors and HER2 can be divided into three biological subgroups: Estrogen receptors HER2 negative HER2 positive Epidemiology A lot more common in women Peak incidence in: Post menopausal women Increases with age 50% of breast cancers are diagnosed in women aged greater than or equal to 65. 2 nd most common cancer overall in Australia and most common cancer in women. 5 th most common related cause of cancer deaths in Australia. Risk factors Germline mutations First degree relative with breast cancer Race/ethnicity Non-Hispanic white women Ashkenazi jewish populations BRCA 1 and BRCA2 Age Age at menarche Late menopause Age at first birth Benign breast disease Estrogen exposure Breast density Radiation exposure Carcinoma of the contralateral breast of endometrium Diet Obesity Exercise Probable small protective effect for women who are physically active. Breast feeding The longer the less the risk. Environmental toxins. Inheritance and genes Mutations in BRAC1 and BRAC2 are responsible for 80% to 90% of single gene familial breast cancers and about 3% of all breast cancers. BRAC 1 gene markedly increases the risk of developing ovarian cancer, whole BRAC2 confers a smaller risk of ovarian cancers, but is more frequency associated with male breast cancers. BRCA1 (on chromosome 17q21) and BRCA2 (on chromosome 13q12.3) are both large genes . BRAC1 associated breast cancers are commonly poorly differentiated and have medullary features. Staging of breast cancer Category 1: Spread to 1 to 3 axillary lymph nodes. Category 2: Spread to 4 to 9 axillary lymph nodes. Category 3: Spread to 10 or more axillary lymph nodes.