Hi, from your detailed and knowledgeable descriptions, I would think that what you have is chronic inflammation, with occasional acute inflammation, possibly combined with some fibrosis inside the nodes.
Inflammation in a node can efface the hilum, the same as lymphoma can do. Being oval is a good sign, as you know, because cancer tends to eventually grow out in all directions and so then becomes rounded.
"They usually grow and shrink"
Lymphoma can wax and wane a little but would over time get bigger and bigger. If yours instead shrink considerably, then think of this: if your body can sometimes kill off a cancer and make the node smaller, why would it stop? Also, compare to how an anti-cancer vaccine trains the immune cells to kill a cancer -- the body wipes out the cancer completely and rather quickly. So the behavior you describe seems much more like inflammation lessening, than cancer cells being sometimes partly killed off.
"they range from 1.5 cm to 4 cm"
Nodes with TB can also get quite large, but just as yours they are oval.
"The lymph nodes are only tender when I’m sick"
Inflammatory cells reacting to, say, a virus cold will produce powerful chemicals that travel and that rouse up other inflammatory cells in a chain reaction.
"an enlarged thyroid as well with nodules"
another possible source starting a chain reaction, though more constant
Plus Lyme and co-infections can do strange things over a long time.
Your self awareness and analysis are terrific - especially regarding how the nodes change depending on if you are sick or not. I don't see any reason for a surgical biopsy at this time. Maybe another FNA eventually.
Can you post the latest sono report? Any cystic or necrotic foci? What about vascularity on Doppler?
and of course possible granulomas inside the nodes from the tick bite
It's good that you posted all of the reports. The one from 2013 is that one that mentioned the missing hila. That's why the radiologist said that although the nodes are probably benign, the possibility still exists about cancer.
The crucial thing is that none of the ultrasounds after 2013 mention missing hila. So the hila were not destroyed by any cancer after all. That's very good news for you.
Nothing else there from the US's or from the biopsy indicate cancer. More good news.
But you do have something unusual going on with your immune system.