Odaat,
once again welcome to the forum. We have had many discussions on statistics and they don't tell the whole story. They don't take into consideration health habits, age, or other major factors. Even though I was advanced stage, where the so called statistics are considerably worse, my RO gave me an 85% chance of 5 year survival (5 years being a benchmark). Your son is very fortunate that it was caught early and it's still only just a "possibility" since they have not completed the full workup. The "gold standard" is the pathology report from a biopsy. Early detection is key to sucessful treatment of this and all forms of cancer.

Until then there is not much we can tell you except the common saying around here is "it isn't cancer until the pathology report says it is". Take a deep breath, go with your son and take very detailed notes. Try to stay unemotional and focused. You will need these notes later in case he have to make decisions about different treatment options IF it comes to that. He should definitely have someone taking notes no matter who it is (like if he is married for instance).

Is he being seen by a ENT or head & neck surgeon? How was it detected?

We also like to recommend that he goes to a comprehensive cancer center before treatment is started for at least a second opinion and preferably treatment as well if applicable.