What Causes A Swollen Lymph Node In The Groin Area?

I brought my son (one year old) to the doctor yesterday due to what I thought was a hernia in his groin. His doctor said it was not a hernia but he has enlarged lymph nodes his neck lymph nodes are also larger. She ordered a blood test that showed very highly elevated liver enzymes and borderline low platelets. He has been acting like his usual self. They sent me to the hospital because she wanted a cat scan done. The hospital decided not to do so but to first take a blood sample again to check to see if it were any sort of virus causing this. From the results that came back so far today those are all negative for a virus. We are scheduled to see a GI on Monday. (Two days away.) But I am so upset and scared. I m looking for any sort of answers as far as possibilities of what this could be? Straight answer without any sugar coating. I just want to know.