What exactly does it mean if your lymph node is swollen?

Infection or tumor: The two common causes of lymph node enlargement are local or general infection; or tumors such as lymphoma, leukemia, and metastatic tumor. It is not feasible to know the cause without a good history, physical examination and may be lab tests and imaging studies.

Monitoring Centers: Lymphatic system absorbs/carries things too big to go into the arteries/veins like bacteria eaten by white cells and digested food. Lymph nodes "taste" the lymph for anything bad like bacteria, viruses, cancers, etc. When it detects a problem, it alerts the immune system and your body reacts. They enlarge in response to the inflammation they create when they react. They shrink when all is well.