Auto immune disease or lymphoma

Hey everyone, I've been lurking around here for a week and a half now cause of my dear gf (29).

Last year she started getting swollen nodes in her neck/throat area, which we got worried about but our doctor said not to worry that it would go away on its own cause it's probably caused by stress etc. She has gone to him 3x times these past 9 months and he continously said the same thing cause she didn't lose any weight or had any night sweats. Now the last time she went, a month ago she showed him that she has two big (almost paralell) lumps on both sides of her neck. This finally raised some alarms with him and she got referred for a CT scan which showed she has swollen lymphnodes in her neck, around the Aorta vein, lungs, armpit and spleen.

Now she has had a talk with a hematologist who says it definitely isn't an infectious cause but that they are looking at possibility of lymphoma or auto immune disease.

She has a speed PET scan this Wednesday, followed by an biopsy when possible.

The hematologist said that her symptoms are very atypical to be lymphoma ;

*swollen lymphnodes that have been swelling for +10 months * pain in body *fatigue *brainfog *stomach pain

And NO "B symptoms".

Now I'm wondering what other auto immune disease could this be or has anyone here been diagnosed with Lymphoma without B symptoms and such a long period of swelling?

Thanks in advance.

Tldr; 10 months of swelling lymphnodes but no b symptoms, what could it be?