it was the right decision to make an appointment! but I think because of the duration of his lymphadenopathy it is less likely to be lymphoma or malignancy!
there are differential diagnosis according to the duration of lymph nodes:
less than 2 or 3 months it's most likely to be an infection
more than 2 months but less than a year it may be malignancy, autoimmune diseases and infection and patient should be examined properly to rule out malignancies!
and lymph nodes which persist more than a year can be said they can't be malignancy and maybe it is infection or autoimmune disease!anyway it's better to consult a doctor about doing a biopsy!
how is his blood tests? has he ever been checked about HIV?