Lymph nodes are one of the important immune organs of the body, and there are two common types of lymph node enlargement: 1. benign enlargement, such as lymph node reactive hyperplasia or non-specific lymphadenitis: including enlargement caused by various infections, connective tissue diseases and allergic reactions. The clinical process is often benign and can be completely recovered within a certain period of time with the removal of the cause. 2.Malignant enlargement: such as lymph node metastasis of malignant tumor, or malignant tumor originating from lymph nodes. Various injuries and stimuli often cause reactive proliferation of lymphocytes and histiocytes in the lymph nodes, resulting in enlargement of lymph nodes, which is called lymph node reactive hyperplasia. Lymph node reactive hyperplasia is common in lymph nodes of the neck, axilla, and groin. The causes of lymph node reactive hyperplasia include bacteria, viruses, toxins, degenerated tissue components and foreign bodies, which can become antigens or allergens to stimulate the lymphatic tissue and cause reactions. For example, mammary gland hyperplasia and thyroid adenoma can cause reactive hyperplasia of lymph nodes in the neck or axilla. Lymph node reactive hyperplasia is a benign lesion, but enlarged lymph nodes can be easily confused with lymph node tumors either visually or microscopically, but their treatment and prognosis vary greatly and should be distinguished. In addition to malignant lymphoma, lymphatic tuberculosis, lymphadenitis and metastatic carcinoma are other diseases that need to be distinguished clinically. If reactive hyperplasia of lymph nodes is found, further examination should be conducted in the hematology department of oncology to identify the nature of hyperplasia. If the lymph node enlargement is obvious, we suggest you to have a lymph node biopsy to clarify the nature of the lesion.