Characteristics and treatment of human epidermal growth factor receptor 2 positive breast cancer: 43,485 cases from the National Cancer Database treated in 2010 and 2011.

•Of 298,937 cases of invasive breast cancer with known human epidermal growth factor receptor 2 (Her2) status diagnosed in 2010 and 2011, 43,485 (14.5%) were Her2 positive.•Her2 positivity was greatest in Asian/Pacific Islanders and least in non-Hispanic Whites.•Compared with Her2 negative tumors, Her2 positive tumors were larger (2.6 vs 2.2 cm, P < .001), more likely to have positive nodes (39% vs 31% P < .001), have lymphovascular invasion (30% vs 20%, P < .001), and be high grade (56% vs 29%, P < .001).•When adjusted for age, race, tumor size, and nodal status Her2 positive tumors were much more likely to receive chemotherapy (odds ratio = 5.5, confidence interval = 5.2 to 6.0) and somewhat less likely to undergo breast preservation (odds ratio = .78, confidence interval = .76 to .80).