Your lymphatic system is in some ways like your body's sewer system. I'm sure you know about the wonders of the circulatory system; your lymphatic system is where your blood cells dump their junk. Normally, your lymphatic system gets flushed out a few times a day. However, sometimes the 'junk' builds up or isn't properly flushed out - like when a person is sick. That's usually when people will notice their lymph nodes are swollen. The lymph node that you say has been there for years - has it been swollen for years, or just palpable? Usually they are slightly palpable. There are lymph nodes near your breasts. In the middle ages, one of the symptoms of Black Plague was enlarged "buboes" - swollen axillary lymph nodes. They're located around your armpits. Lymph nodes are all over the body, not just your neck. Chances are that your body is trying to fight off an infection. I've had badly swolen lymph nodes twice so far - the first time I had been exposed to Cat Scratch Fever (I was lucky not to have the full disease!) and the second time I was fighting a raging strep throat. Depending on how long your nodes have been swollen, your doctor will most likely test you for infections and give you some antibiotic meds. I hope you get better soon!