Reactive lymph nodes, mean cancer?

No.: Generally, when someone describes lymph nodes as "reactive", they mean that the lymph node abnormality / enlargement is caused by a benign condition (such as an irritant or infection or inflammation) and not a malignancy. It is not always possible to determine to what a node is "reacting", but use of the wording "reactive" generally connotes a benign / non-malignant process.

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.