In the United States, breast cancer is the most common form of cancer found in women, and the second biggest cancer killer after lung cancer. If caught early enough, studies have shown that up to 98 percent of women suffering from a localized breast cancer will survive at least five years after initial diagnosis. New and developing therapies have also allowed women with advanced breast cancers to enjoy relatively undiminished qualities of life. Most breast cancers originate in the network of ducts and glands contained within the breasts. The abnormal cells that cause breast cancer can also spread to other parts of the body, such as the lymph nodes. However, cancer metastasis may also occur in bones, lungs, liver, and, less commonly, the brain.

Though there are no proven methods for breast cancer prevention, early detection as a result of regular self and clinical breast examinations or mammography will give a patient the best chance at undergoing a successful treatment. Many health organizations encourage women past the age of 20 to receive a clinical breast examination from their doctor once every three years, in addition to conducting monthly self-examinations. Women over the age of 40 are advised to seek a clinical breast exam and a mammography each and every year.

Diagnosis
There are many different tests that doctors at Mount Sinai use to diagnose breast cancer. Although biopsies are the most common way to make a definitive diagnosis, doctors may also use image tests, including diagnostic mammographies, ultrasounds, or MRI scans. Blood tests are also frequently used to help determine if the cancer has spread outside of the breast.