Ultrasound of the breast is the most commonly used means of breast examination. Ultrasound of the breast can detect nodules and lumps of 0.1 cm or more, and can determine the benignity or malignancy of breast lumps based on their morphology, borders, blood flow, ductal dilatation, and the presence of microcalcifications, combined with the experience of the breast ultrasonographer. Chinese women generally have dense breast glands, so ultrasound is the most common means of screening for breast tumors, especially for young women under 35 years old. The accuracy of ultrasound is more human, and an experienced ultrasonographer can more accurately determine the nature of a breast lump. Mammography can detect lumps that are significantly denser than the surrounding normal glands, as well as microcalcifications and structural abnormalities that cannot be detected by ultrasound, which may be early breast cancer or precancerous lesions. In China, women usually have a higher density of glands and mammography is more suitable for middle-aged women over 35 years old, especially after breastfeeding, and a single mammogram may miss smaller lesions. Mammography is not a substitute for ultrasound. It is complementary to ultrasound, and the two can be used as a reference for each other to diagnose breast tumors more accurately. Many patients and some doctors feel that mammography is a more accurate test than ultrasound, which is a common misconception. With breast MRI, in general, ultrasound of the breast plus mammography can detect nearly all breast lumps and determine their nature. However, for some lesions that are difficult to diagnose, especially if the ultrasound diagnosis is unknown and the patient is not suitable for mammography (e.g., if the patient has had breast augmentation surgery), MRI is one of the tools to further clarify the nature of the lesion. However, MRI examinations are too sensitive and may result in overdiagnosis, leading to overtreatment. In addition, it is difficult to localize the small suspicious lesions found by MRI, and even if the lesions are found, they are difficult to remove surgically, so it is not widely used clinically and is only used as a supplemental test to breast ultrasound and mammography.