I have 3 swollen lymph nodes. two in my neck and one under my chin. have had one for several years. other two are a couple years old. possible cancer?

Follow up: Benign lymph nodes tend to be mobile and less than 1 cm in size. Malignant lymph nodes tend to be greater than 1cm and are usually more firm and fixed. Are you having any associated night sweats, fatigue/lethargy? I recommended you get them examined by an ENT. They may watch and wait, order head/Neck CT scan, or even order FNA/biopsy of the largest lymph nodes with pathology evaluation. Follow up.

That's normal: The average young person your age, based on my examining healthy medical students over decades, has 2-4 palpable lymph nodes in the neck. If they're stable, and not preposterously enlarged, don't give them another thought and be thankful for good health -- they're your friends, protecting you. Best wishes.

Not cancer: The presence of a newly defined lymph node that is firm and probably larger than 1 cm. has to be observed for possible malignancy. The observation process depends on noting within a period of time, say 1-2 months that the node is getting larger, firmer and increasing in number. This then suggests bx. For 3 nodes to be present for an extended period and not progress indicates a benign situation.