A hyperechoic nodule of 2.1*0.8cm in the subcutaneous area of the neck with clear boundary, regular shape and visible blood flow signal may be a localized cyst, enlarged lymph node or lipoma. 1. Localized cysts: cyst-like lesions may be formed in the subcutaneous soft tissues of the neck, such as sebaceous cysts, etc. Cystic tissues often have an external envelope, and ultrasound examination may show internal blood flow signals. 2. Lymph node enlargement: if the body is infected by bacteria or viruses and other pathogens, the lymph node tissues may have reactive hyperplasia to form lymph node enlargement and lymphadenitis, and localized hypoechoic nodules will also be found in the examination, and the morphology is relatively regular. Lymphatic metastasis of malignant tumors to subcutaneous lymph nodes in the neck in the early stage may also appear in this situation. 3. Lipoma: due to the deposition of subcutaneous adipose tissue, sometimes lipoma will be formed in the subcutaneous neck, and the boundary with the surrounding tissues is relatively clear. If a 2.1*0.8cm hypoechoic nodule is found under the skin of the neck, and if the border is clear, the morphology is regular and blood flow signals may be present, it is recommended that regular review be conducted and surgical resection may be considered if necessary.