Whether a single full lymph node in the armpit is good or bad depends on the specific type of disease. Benign lymph node enlargement is commonly caused by infections, such as lymphadenitis caused by mastitis, in which case the prognosis is better; there may also be malignant diseases such as lymphoma, lymphoma metastatic cancer and other malignant diseases, in which the prognosis is relatively poor. 1. Acute lymphadenitis and other benign diseases: when inflammation occurs in the tissues around the lymph nodes, it may lead to axillary lymph node fullness, i.e. lymphadenitis, such as mumps, tonsillitis, mastitis, etc. Lymphatic tuberculosis can also lead to this kind of lymphadenitis. Lymphatic tuberculosis can also lead to this kind of phenomenon. 2. Lymphoma and other malignant diseases: lymphoma attacks the axillary lymph nodes, which can also lead to axillary lymph node single fullness, often accompanied by fever and other systemic symptoms. In addition, lung cancer, breast cancer and other diseases can be transferred to a single lymph node in the axilla through lymph nodes, which is characterized by enlargement of the lymph node, hard texture, no tenderness and poor mobility. There are other reasons for single lymph node fullness in the armpit, so it is recommended to consult a doctor in time, complete other examinations, and cooperate with the doctor for active treatment.