There are 3 common causes of enlarged lymph nodes: 1. Benign enlargement. This includes enlargement caused by various infections, connective tissue diseases and allergic reactions. They are often clinically benign and can recover completely within a certain period of time as the cause is removed. 2. Malignant enlargement. It includes malignant tumors originating from lymph nodes, such as lymphoma, lymphocytic leukemia and malignant histiocytosis, and lymph node metastases from other malignant tumors, such as lung cancer, gastric cancer and breast cancer. The lymph nodes are persistently and progressively enlarged, and if not actively treated, they often deteriorate progressively and lead to death. 3. Enlargement between benign and malignant. Such as vascular primitive immune cell lymphadenopathy and vascular follicular lymph node hyperplasia. They are often benign at the beginning, but can become malignant and fatal. Therefore, after determining the enlargement of lymph nodes, it is crucial to determine their cause and nature. Local enlargement with obvious pain often suggests infection; progressive painless enlargement often suggests malignant neoplastic disease. The diagnosis can usually be made through physical examination, ultrasound, film, puncture or biopsy by doctors, combined with other clinical symptoms and laboratory tests.