The American Cancer Society projects that more than 271,000 people will be diagnosed with invasive breast cancer this year, and more than 41,000 will die from the disease.

Breast cancer is the most common cancer diagnosed in American women, excluding skin cancers. Though rare, men also can be diagnosed with breast cancer.

Being a woman and getting older are the greatest risk factors for developing breast cancer. But inherited changes in genes – such as BRCA1 or BRCA2 – and prior radiation exposure can also increase risk. Racial disparities exist in mortality. Despite a similar incidence, mortality from breast cancer among black women is 40% higher than that of white women, according to the American Cancer Society.

The U.S. Preventive Services Task Force currently recommends biennial screening mammography for women aged 50-74 years, though they caution about the harms of overdiagnosis with regular screening. 

A pathologist typically confirms a breast cancer diagnosis after a biopsy and identifies the cancer as either luminal A (HR+/HER2–), luminal B (HR+/HER2+), HER2-enriched (HR–/HER2+), or triple negative (HR–/HER2–). The biopsy may be used to look for other biomarkers, such as a BRCA mutation, and to determine recurrence scores, based on further genomics of the tumor. Broader genomic testing, to guide treatment, is currently under debate.
Primary breast cancer, which has not spread to distant sites, is treated with a combination of surgery, radiation, chemotherapy, HER2-directed therapy, and/or hormonal therapy, depending on biopsy findings and clinical factors.

About 6% of those diagnosed with breast cancer are diagnosed with de novo metastatic breast cancer. The disease has spread beyond the breast, most typically to the bones, lungs, liver, or brain. Others with metastatic spread of the disease are diagnosed with a distant recurrence up to several years, even decades, after their initial breast cancer diagnosis. Treatment for metastatic disease can include HER2-directed therapy, hormonal therapy, immunotherapy, chemotherapy, and radiation therapy. Newer agents to treat metastatic disease include CDK 4/6 and mTOR inhibitors.

Methods for measuring disease progression in patients with advanced breast cancer continue to be refined. Circulating tumor cells and tumor DNA currently are being evaluated for monitoring disease and predicting response to treatment.