Tiny lymph nodes, about 0.5 cm, on right anterior clavicle, and r and l supraclavicular areas. rubbery and moveable. no night sweats or fever. cause?

Supraclavicular node: Supraclavicular nodes never should be ignored. At your age, my biggest concern would be some type of lymphoma. You don't have to have night sweats or fever - these just classify stage if you have lymphoma. I have rarely seen these nodes enlarge with mono, but I would consult an oncologist if your primary care doc doesn't refer you for biopsy.