While I cannot totally rule out the possibility of JL in this case, the
presentation and the information that we have - sketchy as it is is not
overly consistent with a diagnosis of JL.  (You can find more information
on lymphoma at my web site at http://www.afip.org/ferrets .)
 
Let's look at the situation - JL usually presents as a neoplasm which
affects the organs of the body, rather than the lymph nodes (which is
seen in the adult onset forms).  When first diagnosed, there is usually
advanced disease in the liver, spleen and thymus, resulting in swelling
of these organs.  Most cases of JL are seen only after the thymus has
increased in size to where it is compressing the lungs and breathing is
difficult (this is why the average life span of untreated JL is about two
weeks, as compared to several months when treated aggressively.
 
Now your ferret has no described evidence of any organ enlargements on
the X-ray, and races around the house - not what you would expect with JL.
While I can't tell you what the mass in the abdomen is, I think that the
best thing to do is to have it taken out an evaluated - no sense messing
around.
 
Also, if he is not eating well, then don't expect a lot of poop.  Another
possibility here in a young ferret would have to be a GI foreign body -
they can occasionally mimic abdominal masses.  I note that no bloodwork
has been run - an oversight if JL is a serious consideration.
 
My suggestion - let's see if you can get a referral to address this a
bit faster than two weeks - the office can probably give you the name of
someone locally who can handle a good abdominal exploratory.
 
With kindest regards,
Bruce Williams, DVM
[Posted in FML issue 3490]