There are about 600 to 700 lymph nodes in the human body, and palpation can only reach superficial lymph nodes in various parts of the body. In healthy people, superficial lymph nodes are small, no more than 1 cm in diameter, soft, smooth, movable, not easily palpable, and without pressure pain. When inflammation or cancer occurs in a part of the body, microorganisms or cancer cells can spread along the lymphatic vessels and reach the lymph nodes in that organ or part of the body, causing swollen lymph nodes and pressure pain, and thus are important for disease diagnosis. Swollen lymph nodes are most often found in the neck and can have many causes. Some children usually have swollen lymph nodes in the neck. These lymph nodes are usually small, such as the size of a green bean or soybean, do not feel painful, and can be 1 to 2 or more, with no significant change in size for months or even years. This may be related to dental disease, pharyngeal infection or chronic infection of the oral and maxillofacial region. Swollen lymph nodes are often a manifestation of certain diseases, and some of the diseases that cause swollen lymph nodes are listed below: 1. Non-specific lymphadenitis: acute lymphadenitis due to local inflammation of nearby tissues, common ones such as purulent tonsillitis and gingivitis can cause swollen lymph nodes in the submandibular or cervical area. Acute lymphadenitis has a soft texture, pressure pain, and a smooth surface without adhesions; in the chronic stage, the texture is harder and the pain is mild. After anti-infection treatment, the lymph nodes can be significantly reduced or disappear. 2. Lymph node tuberculosis: The lymph nodes are obviously enlarged, often as a string of enlarged lymph nodes, but they may also exist in isolation, with or without pain, and the patient may or may not have fever. Lymph node tuberculosis often occurs in the lymph nodes around the blood vessels in the neck, with varying sizes, soft texture, and may have adhesions, which may break down and develop fistulas in advanced stages, making it difficult to heal and forming purpura after healing. 3.Lymph node reactive hyperplasia: reactive hyperplasia occurs in lymph nodes under the stimulation of repeated inflammation, which cannot subside significantly by anti-inflammatory treatment and can be clearly diagnosed by excisional biopsy without special treatment. 4. Subacute necrotizing lymphadenitis: the lymph nodes are obviously enlarged and painful, and the patient may have a fever that persists, sometimes the fever can last for 2 weeks or longer, and the blood chemistry tests have reduced white blood cells. In many cases, a lymph node has to be surgically removed for pathological examination before a definitive diagnosis can be made. Subacute necrotizing lymphadenitis is a treatable disease, and the vast majority are cured. 5, acute leukemia: acute leukemia lymph node enlargement can be large or small, generally no pain sensation, the patient mostly feels tired and weak, not eating, always feverish, as if the cold, bronchitis and other infections always recur, while in the past there was no such performance. Anemia (decreased hematocrit) will be found if blood tests are performed. Some patients have bleeding spots on the skin or cyanotic spots, which are caused by leukemia, and blood tests reveal reduced platelets. All leukemia patients have abnormal blood tests, but a bone marrow aspiration must be performed to obtain bone marrow tests to determine the diagnosis. 6. Malignant lymphoma: The lymph nodes are enlarged significantly and do not feel painful, but they can also have weakness and fever, and grow faster. Sometimes the “visceral” lymph nodes are also enlarged and can only be detected by ultrasound or CT. Doctors have to remove a lymph node through surgery to do pathological examination to confirm the diagnosis. 7.Metastatic malignant tumor: Malignant tumors in various parts of the body can metastasize to the lymph nodes, for example, oral cancer mostly metastasizes to lymph nodes in submandibular, upper neck and preauricular area, stomach cancer can metastasize to enlarged lymph nodes in left supraclavicular region, nasopharyngeal cancer metastasizes to lymph nodes in upper neck, chest cancer can metastasize to lymph nodes in right supraclavicular or axillary region. The metastasized lymph nodes are hard, painless, easily adherent and fixed, and grow faster. 8.Infectious mononucleosis: This is also a disease caused by a virus, which is called EBV. In addition to swollen lymph nodes, the patient also has a fever and can have other manifestations, such as a large liver, a large spleen, a rash, and changes in the patient’s blood tests. Because this disease behaves like other blood disorders, doctors take it seriously and perform appropriate tests to prevent misdiagnosis. Treatment for infectious mononucleosis is effective. Swollen lymph nodes can also occur in many other diseases that cannot be listed here. In conclusion, if swollen lymph nodes appear, they should be taken seriously and promptly seen.