There are many reasons for lymph nodes 1.9 cm under armpit, which may be caused by lymphadenitis, which is generally not serious; it may also be caused by lymph node tuberculosis, which is actively treated and has a better prognosis; if it is caused by metastatic cancer, it has a worse prognosis and is more serious. 1. Lymphadenitis: when tonsillitis, sinusitis, mumps and other infectious diseases occur, lymph nodes can be enlarged around their tissues, including axillary lymph nodes, which can be improved by treating the primary disease and the prognosis is good. If chronic lymphadenitis is formed, it needs to take antibiotic treatment for a long time. 2. Lymph node tuberculosis: the lymph nodes under the armpit can be 1.9 cm, usually adhered to the surrounding tissues, usually accompanied by low fever, night sweating, weight loss, malnutrition and other symptoms, after the joint application of isoniazid, rifampicin and other anti-tuberculosis drugs, regular treatment, generally a better prognosis. 3. Lymph node metastasis of cancer: Generally, lung cancer, breast cancer and so on can have lymph node metastasis under the armpit. Lymphoma, lymphoblastic leukemia and other diseases can also invade the lymph nodes here. The prognosis of lymph node enlargement caused by these malignant diseases is poor. Lymph nodes under the armpit 1.9 cm may also be caused by other reasons, such as small game lupus erythematosus, etc. It is recommended to consult a doctor in time, complete the examination, and follow the doctor’s instructions to treat accordingly after a clear diagnosis.