There are two primary uses for breast ultrasound:
To determine the nature of a breast abnormality
When a mammogram or self examination reveals an abnormality, breast ultrasound may be used to help diagnose and characterize it. With ultrasound, it is possible to determine if the abnormality is a non-cancerous (benign) lump of tissue or a cancerous (malignant) tumor.
Supplemental breast cancer screening
Although mammography is the only screening tool for breast cancer that is known to reduce deaths due to early detection, it does not detect all breast cancers. Some breast lesions and abnormalities are not visible or are difficult to interpret on mammograms, especially in breasts that are dense. Screening ultrasound can be an alternative to breast MRI in some cases, such as in women with dense breasts, women with implants, women who are pregnant, or women who may be unable or unwilling to have a breast MRI performed.