Possible causes of painless lymph nodes include: lymphoma, lymph node metastasis of malignant tumors, nodal disease, lymph node tuberculosis, etc. 1. Lymphoma: Lymphoma is a malignant tumor originated from lymphatic tissues, which mainly manifests as painless progressive enlargement of lymph nodes on the body surface, commonly found in lymph nodes in the neck, armpit and inguinal area. In addition, there will be fever, night sweats (abnormal sweating after going to sleep and stop sweating after waking up), fatigue, itching and other systemic manifestations. 2. Lymph node metastasis of malignant tumors: lymph node metastasis of malignant tumors can cause painless enlargement of lymph nodes at the initial stage, for example, breast cancer metastasis to axillary lymph nodes, lung cancer metastasis to supraclavicular lymph nodes, thyroid cancer metastasis to cervical lymph nodes and so on. When the enlarged lymph nodes press the neighboring nerves, it will cause pain. 3. Nodular disease: Nodular disease is a kind of inflammatory granulomatous disease, which mainly involves the lungs and lymph nodes. It can cause painless enlargement of lymph nodes on the surface of the body, but they do not fuse with each other. Lymph nodes in the neck, medial epicondyle of the humerus, and inguinal region are common. 4. Lymph node tuberculosis: Lymph node tuberculosis is caused by mycobacterium tuberculosis invading the lymph nodes, mostly located in the cervical lymph nodes, manifested as painless enlargement of the affected lymph nodes, accompanied by low-grade fever, night sweats and other tuberculosis poisoning symptoms. Initially, the enlarged lymph nodes can be pushed, and then the lymph nodes can merge with each other to form a mass, and abscesses and fistulas may be formed. It is recommended to go to the hospital as soon as possible to clarify the nature of the lymph nodes and provide targeted treatment.