Lymph nodes are part of the lymphatic system which is also our 'defense' system. They serve to trap germs that may be circulating in our body. They drain lymphatic fluid from organs near where the nodes are located.
For example, any disease in the head and neck areas may cause enlargement of nodes in the neck. They also may trap cancer cells if present in any particular part of the body. Both infectious and cancerous processes can cause enlargement of the node, which may be rapid or gradual. The enlarged nodes may or may not cause pain. It does not automatically mean that cancer is present.
If the enlarged node is accompanied by certain symptoms or signs that point towards infection or inflammation, antibiotics may be tried first. If they don't settle after one or two weeks, then a biopsy is indicated to find out the cause. Many cancers can cause enlargement of nodes near where they happen, eg breast cancers causing enlarged nodes in the axilla. There is also a type of cancer called lymphoma where the cancer occurs primarily in the lymph nodes.
Therefore it is important not to ignore them. Usually, they will settle if it's not caused by cancer. Anything that persists beyond 1-2 weeks should be looked at by a doctor.
