You have a sore throat and then feel some bumps on your neck. Being neurotic (and believe me I know about neuroses), you immediately assume that you have developed some awful, terminal cancer. You rush to your doctor who, after your rapid fire description about your potential last days on the planet, smiles and tells you you have a strep throat and nothing more.
Those bumps on your neck are simply lymph nodes. Lymph nodes are, if you will, the watch stations of the immune system. If there is an infection, then often times the body will respond with a multi prong attack-antibodies, inflammatory chemicals and killer cells. Lymph nodes help control the response. What this means is that if the system senses an invader then the lymph nodes will increase in size in order to help mount a response.
That is not to say however that swollen lymph nodes mean only that there is an infection somewhere in the body. They can also become enlarged due to inflammation from other causes than infection.
For example, autoimmune diseases such as rheumatoid arthritis cause inflammation along with lymph node enlargement. So too will cancer, where the body tries to fight the cancer and again the lymph nodes grow in size. However, these lymph nodes are more likely to be firm, nontender and not so easily movable. Furthermore, these nodes don’t just appear overnight, as in the case of infection. They will slowly enlarge and be there for awhile.