Ultrasound should be expressed as B ultrasound. If the diameter of the breast nodule is small and fails to reach the diagnostic index of ultrasound, or if the patient’s localized fat layer is thick, the breast nodule cannot be detected by ultrasound. Ultrasound is an examination method to diagnose breast nodules. During the examination, if the diameter of the patient’s breast nodule itself is relatively small and there is no obvious clinical symptom, which fails to reach the diagnostic index of the disease, it may not be detected when the examination is carried out. In addition, due to the patient’s localized thick skin fat layer, the ultrasound imaging is interfered with, resulting in the failure to detect the breast nodule. If breast nodules cannot be detected by ultrasound examination, it is recommended to go to the hospital in time and choose the appropriate examination method under the guidance of the doctor to make a clear diagnosis, so as to avoid delaying the condition.