A breast nodule on a breast ultrasound but not on a mammogram may be due to the difference in sensitivity between color ultrasound and molybdenum. Mammogram is sensitive to calcification and ultrasound is sensitive to soft tissue. Due to the high sensitivity of breast ultrasound to soft tissue, clinical breast ultrasound examination of breast hyperplasia, breast fibroadenoma are more sensitive, can better show the size and shape of the nodule. The first choice for clinical breast examination is color ultrasound at the age of 35. It is because at this time the breast is dense, molybdenum target is not as sensitive as ultrasound to soft tissue. However, if there are calcified spots in the breast, the detection rate of molybdenum target is higher than that of ultrasound. Both ultrasound and mammography can diagnose breast cancer, however, mammography has a higher detection rate for small calcifications. Clinical ultrasound and mammography are often combined for diagnosis.