Your doctor may order a breast ultrasound if he or she discovers a lump during a clinical breast exam or something suspicious appears on your screening mammogram. The ultrasound is a diagnostic test for evaluating breast tissue that allows for close examination of cysts, lumps or other abnormal areas within the breast. In fact, it is one of the most-used tools for evaluating breast glands and assisting in biopsy and needle localization procedures. This painless test simply involves your physician or radiologist holding a special transducer against the skin so as to produce an image of the tissue within onto a computer monitor. In most cases, a breast ultrasound can be performed in a matter of minutes.