Breast ultrasound (or sonography) is an imaging technique for diagnosing breast disease. It uses harmless, high frequency sound waves to form an image. A gel is applied to the breast to remove any air that may be between you and the transducer. The sound waves pass through the breast and bounce back or echo from various tissues to form a picture of the internal structures.
Breast ultrasound is often recommended when an abnormality is seen on a mammogram. The ultrasound helps to determine if the abnormality is solid or if it contains fluid. A structure which has certain characteristics that prove it to be a simple cyst can be confidently diagnosed as benign (non-cancerous).