Hmmm. Apart from that fever, it sounds like a deficiency case. Was the fever based on body temperature or his temperature preferences? What were his preferences? Was he chilly?
Palpable abdominal masses were interpreted as Blood stasis by the Nan Jing. It was felt that if you could palpate the boundaries of a mass intra-abdominally, it couldn't be anything but Blood stasis. In that case, then, something depending on the preferences of the cat, you could think of Ge Xia Zhu Yu Tang (cat is hot) or Shao Fu Zhu Yu Tang (cat is cold). The latter is not a bad choice, actually, given the deficient picture. I've used it for lymphadenopathy in dogs secondary to perianal adenocarcinoma and have seen it relieve secondary large bowel obstruction. So if the owner reports your acupuncture treatment worked, it's a consideration.
The last idea I have depends on whether you've ruled out infection as a cause of the lymphadenopathy. If not, then Bu Zhong Yi Qi Tang is an option. It's a 'mover' and a tonic, is an immune and appetite stimulant, and stimulates the bone marrow to address the anemia. So it's got a lot going for it biochemically. If infection hasn't been ruled out, then I'd give it a try.
All the best,
Steve