I'm 18, have one swollen lymph node under chin won't go away 3 docs said not to worry, post nasal drip won't go away. cancer ? help please

Neck node: You have seen 3 different doctors for the enlarged lymph node and despite being told by these medical professionals that it is just a normally reactive node to some sinus inflammation, you are concerned about "cancer" at 18? I suspect you have anxiety disorder that may not be properly dealt with. Ask for treatment of your sinusitis or allergic rhinitis and see if it resolves. unlikely neoplastic.

Reactive node: If the lymph node is easy to move around and is not getting bigger it is likely reactive meaning your body is mounting an immune response to fight off infection.

DOUBT Cancer!: Mild lymphadenopathy is very common with cold symptoms and can even be allergy mediated at this time of the "Fall Allergy Season." It may take weeks for the swelling to go down. The more you feel the node and palpate it, the longer it will stay enlarged and the more likely it will get irritated. Try rest, fluids, and ask your Dr. for an inhaled corticosteroid nasal spray to help with the PND.