There have recently been several discussions on lymphoma at the Ferret
Health List at Smartgroups.  Those will help you for medical approaches.
http://www.smartgroups.com/groups/ferrethealth
or you could find some of them from vets that were carried to the FML in
just the last few days.
 
Personally, in your situation we'd go with high levels of pred ***IF***
we were reasonable confident that it is lymph after careful checking.
 
How long have the other problems been going on?  Only very recently?  I
ask because lymphosarcoma/lymphoma can also cause those symptoms if it
settles in those organs; we've been through it causing both, so it might
be just one form of malignancy but in multiple organs so multiple
symptoms.
 
Nodes can also be swollen from infection, and certainly if a ferret is
sick the risk of infection is higher.  Since you didn't mention that the
lower nodes are also up this increases the chances that what you are
feeling is fat, or swelling from infection.  This needs a vet assessment,
and if the vet thinks it may be the nodes then first a run of antibiotics
if the vet thinks there might be an infection, and if worrisome in the
vet's assessment then at least an aspiration but preferably a pulled node
to go for biopsy.  The ONLY way to know if there is lympho is to do a
biopsy!
 
Adrenal neoplasia is usually NOT malignant, but it CAN cause fat deposits
in piles of places beyond the abdomen even if benign.  Around nodes is
one of those places the fat can be laid down.  Heck, sometimes it even
causes fat to be deposited in the thorax which can be fatal if organs are
too crowded.
 
What makes this ferret not a surgical candidate?
 
It is possible to have multiple things going on at once, but to have
insulinoma not caused by lympho, and adrenal neoplasia not related to
lympho, and lympho all together is very rare.  We've been there, but it
is very rare.
 
If you consider the assorted herbal approaches then get a full heart
work-up with EKG/ECG and an ultrasound FIRST before starting them because
several of the common ingredients in those (like ginsengs and true
licorice) are dangerous to hearts so if any circulatory disease is
present they have to be avoided like the plague.  We have not used them
due to the strong circulatory risks that are known to be caused by some
of the ingredients.
[Posted in FML issue 3864]