What are the chances of me getting cancer at 20? im always having pain in my neck and throat and im concerned. seen my pcp but didn't seem concerned.

Low: Given your age your chances of having a cancer are low. With this being said what makes you think cancer, do you have immediate relatives who were diagnosed with cancer, any other symptoms? There still should be an answer for your pain/ discomfort, but would look first for much more common causes: allergies, musculoskeletal pain, anxiety making your pain feel worse, etc.

Rare: Cancer for the most part is a 3 step procedure in that if one event occurs, the patient is still free of disease. To have a 3rd hit such as an additional viral or carinogenic effect taking place in the 20's is rare. Most tumors at an early age occur because of inherited genetic defects.