5 year old in terrible pain

My son has been having exteme stomach pains for the past three months and doctors have given various diagnosis: gas, physcosomatic, stomach infections. But upon doing an ultra sound, it was found that he has swollen lymph nodes in his stomach. Can you give any indication as to what may be the possibilities.

(His grandfather was diagnosized with a malfunction lymphatic system and has swollen lymphs about his body.)

[Kar0909]

My suggestion is get more tests.  My son had the symtoms (symptoms) given and they tested him for several things until I INSISTED they were wrong, it took many doctor visits....  My son had cancer at the age of 22 months.  It's rare called neuroblastoma, I highly doubt that that is what your son has, but insist on tests! Your his mom and you know when things aren't right!!!