Hi, there is still some chance that it's not cancer. There are even some rare possibilities wherein it's not an infection, such as 'inflammatory pseudotumor' or Rosai-Dorfman disease. Inflammation can sometimes wipe out the fatty hilum and result in some new blood vessels.
Hopefully you can speak to the surgeon immediately after the biopsy to ask if he saw any signs one way or the other.
If it is lymphoma, then it's more likely because of his age to be Hodgkins Lymphoma, which has a better outlook than non-Hodgkins Lymphoma. At his age there is also a very high chance of successful treatment and, in fact, the worry might be more about what will be twenty years in the future - rather than what's in store for 3-5 years from now.
Did the nodes all pop up very suddenly and then stop growing and multiplying? That could tend toward infection. You'd want to consider if there was exposure to a pathogen.
You'd also want to consider if there is a family history of unusual immune conditions.
I would definitely look into As as a possible alternative cause. I just had a couple of minutes for right now and found two case reports.
Am J Med. 1986 May;80(5):951-3.
Diffuse lymphadenopathy as a manifestation of ankylosing spondylitis.
Clin Rheumatol. 1998;17(5):412-5.
Lymphadenopathy in an oriental with ankylosing spondylitis.
Not recent though.
Have you ever looked into the association of As with Klebsiella bacteria?
There are ways besides cancer that nodal architecture can be effaced, as mentioned above. Granulomatous disease is another one and TB is known for that. Some types of Klebsiella do that, too. Nothing is an exact match, but if your son has something other than a cancer, it's likely rare and somewhat unexpected, but can be similar to conditions like TB or Granuloma annulare while also being different in some ways from them.
That's something to hope for, anyway. But a scan probably won't differentiate.