cat with very swollen lymph nodes

My 2 year old russian blue cat, Oggy,  has very swollen lymph nodes in his neck and rear legs. He is otherwise healthy with no other symptons.  My vet aspirated the nodes which showed no sign of lymphoma or infection. A blood test was negative for feline aids, leukeamia, and his white blood count was normal. There was a slight elevation in liver enzymes.
My vet does not know what it is and that we will just watch him for the moment.
These swellings are quite alarming and I am very worried about him. It would be very expensive for me to take him to a specialist vet.
Does any one have any idea what this could be.

Thank you.

[nancyjac]

Was he tested for FIP (feline infectious peritonitus)?  Liver issues sometimes present as a result of Corona virus or FIP.  How is his appetite?  Does he seem to be dehydrated at all?  The swollen lymph nodes in his throat could affect his ability to eat, drink, and swallow.

[debra56]

Thank you nancyjac,  I'm not sure if Oggy was tested for FIP, my vet did not mention it, but his appetite is normal and he drinks plenty of water. He eats and drinks with no problem and in fact displays no other symptoms other than the swellings. No diarrhea or listfulness.
It is very strange.

[Eaglemom15]

Did you every find out what was wrong with Oggy?  My cat has the same problem and the Vet ran the same tests.  All were negative.