A 3mm lymph node is similar to the size of a small grain of rice and a half and is within the normal range. Normal people’s lymph nodes are usually around 3mm to 4mm, and the maximum size will not exceed 8mm. If it exceeds 8mm, it is called enlarged lymph nodes, and basically, it can be diagnosed as lymphadenopathy, which may be benign or malignant, benign lesions include viral infections or inflammatory stimulation, and malignant lesions are usually caused by tumors. If it is caused by viral infection or inflammatory stimulation, it can be treated with oral antiviral and anti-infective drugs. If it is caused by tumor, it needs to be surgically removed, and radiotherapy is needed if necessary. If lymph node enlargement occurs, Doppler examination is needed to clarify the diagnosis, and if malignant lesions are suspected, biopsy pathology examination is needed.