What are lymph nodes, and why do you keep checking them?

They are small filters spread through the body, joined by channels. Fluid drains through them, and they help fight infection. They are also the first place a cancer often travels to.

So checking them tells us how far things have gone. Cancer in a lymph node does not mean it is everywhere. It means it reached the first filter, and that changes the plan rather than ending it.

Written by two physicians. Checked against patient information from the US National Cancer Institute and Cancer Research UK.