The greatest utility for ultrasound of the breast is in the differentiation of cysts from solid masses. After complete, high quality x-ray mammography, a palpable mass or nonpalpable mammographic abnormality may remain indeterminate in etiology, and ultrasound may be useful as an adjunctive diagnostic modality. However, present ultrasound technology is poor for visualization of small solid masses, particularly in fatty breasts, and it cannot reliably detect microcalcifications. Therefore, sonography has no role in screening for breast cancer.