Ultrasonography can help diagnose cancers such as liver cancer, breast cancer, lymph node metastasis, etc., but the final diagnosis still needs to be based on pathological examination. 1. Liver cancer: ultrasound is a non-invasive examination that can diagnose malignant tumor of liver, which shows round soft tissue nodules with low echogenicity under ultrasound, and obvious blood flow signals can be seen in the nodules. 2. Breast cancer: ultrasound is of great clinical significance for the diagnosis of breast cancer, which can evaluate the growth size of the tumor, whether the internal echo is regular, whether the boundary is clear, and whether the blood flow signal is clear. 3. Lymph node metastasis: lymph node metastasis cancer manifests as enlarged lymph nodes, under ultrasound, it can be found that the peripheral membrane is incomplete, the structure of lymph nodes is blurred, and there are blood flow signals in them. Ultrasound has certain diagnostic significance in diagnosing cancer, and can even be found in early stage, but the most important diagnosis still relies on pathological examination.