Axillary lymph nodes 2.5 cm large is problematic, the general diameter of the lymph nodes in the 0.5 cm or less, the diameter of more than 0.5 cm even if the enlargement, is not normal phenomenon. Axillary lymph nodes 2.5 cm may be caused by infectious factors, tumors, junction tumors and other reasons. 1. Infectious factors: If the patient is infected by pathogens (commonly bacteria, viruses, tuberculosis bacillus, etc.), which induces an immune reaction in the axillary lymph nodes, it will lead to the enlargement of axillary lymph nodes. 2. Tumor: lung cancer, stomach cancer, breast cancer and other malignant tumors can metastasize to axillary lymph nodes, resulting in the enlargement of lymph nodes in this area, which reaches or exceeds 2.5 cm, and its clinical manifestation is the continuous development of axillary lymph nodes, which can worsen the condition of the patient and even lead to death if the patient is not treated in time. 3. Junctional tumor: mainly vascular follicular lymph node hyperplasia, vascular primitive immune cell lymphadenopathy and so on will appear the phenomenon of axillary lymph node enlargement. Axillary lymph nodes 2.5 cm should consult a doctor in time, exclude the disease under the examination of a professional doctor, and treat the symptoms to avoid the development of the disease.