Whether axillary lymph node 15mm is serious or not is mainly determined by the results of pathological examination. It is not serious due to inflammation, but more serious if it is caused by tumor. If the axillary lymph node 15mm is caused by inflammation, this situation is not very serious, you can take anti-inflammatory drugs under the guidance of the doctor for treatment, such as cefixime tablets, amoxicillin capsules, through regular treatment can make the lymph nodes return to normal size. If the lymph nodes in the armpit are 15mm caused by lymphoma or breast cancer, this situation is more serious, and once diagnosed, it is necessary to carry out timely surgical treatment, and later need to carry out chemotherapy to kill the cancer cells in the body and reduce the chances of recurrence. During the treatment period, patients should have regular checkups, and if abnormal symptoms appear, they need to consult the doctor in time to avoid aggravation of the condition.