Axillary lymph nodes with clear corticomedullary demarcation and thickening of the cortex is one of the findings of axillary ultrasound, which may be due to reactive hyperplasia of lymph nodes, tuberculous lymphadenitis, malignant lymph nodes and other reasons. 1. Reactive hyperplastic lymph nodes: generally, reactive hyperplasia of lymph nodes is benign, usually caused by tonsillitis, pharyngitis or upper respiratory tract infections, which leads to axillary lymph node cortical and medullary demarcation of clear part of the cortical thickening. 2. Tuberculous lymphadenitis: in general, lymph node tuberculosis is common in children and young people, it is an inflammation of lymph nodes caused by Mycobacterium tuberculosis infection, which leads to thickening of axillary lymph nodes with clear corticomedullary demarcation and thickening of the cortex, and it can occur in almost all of the human body’s lymph nodes, and it is more common in the cervical lymph nodes, bronchial lymph nodes and mesenteric lymph nodes, and it is particularly common in cervical lymph node tuberculosis. 3. Malignant lymph node: malignant lymphoma is usually seen in lymphatic enlargement in many places of the body, which will lead to thickening of the cortex of axillary lymph nodes with clear demarcation of the corticomedulla, which is a systemic disease of lymphatic system with cancerous transformation. Axillary lymph node corticomedullary demarcation clear part of cortical thickening need to go to the hospital in time to confirm the diagnosis, under the guidance of the doctor’s instructions for standardized treatment, so as to avoid delaying the condition.