Almost all tests for Malachi are in - just a few gene tests are left and they are expected to be negative. All cultures (microbes of various types) were negative.
The final path results say that he has Rosai-Dorfman disease which is very, very, very rare. It is a subset of histiocytic disorders and all of those disorders affect less than 200,000 people. It is benign and one of the symptoms is massive lymph nodes in the neck because a white blood cell called a histiocyte accumulates in the lymph node. Treatment only occurs if the accumulation of the histocytes causes issues with various organs or other body parts. It is self limiting and all swellings can go away on their own, come and go or not go away. The cause of this disease is entirely unknown. The ENT has called Children's and the University of Chicago for more information and to figure out who we should see next.
That is all that I know right now.
So good news over all but having a very rare disease of unknown origin is not really comforting.