Should I do an FNA on my 15 year old medically complex cat or wait and see?

I’m looking for advice regarding my 15 year old cat, who has hyperthyroidism, chronic pancreatitis, stage 2 CKD, and a possible diagnosis of IBD vs. lymphoma.

An ultrasound showed intestinal thickening and mildly darkened (but not enlarged) lymph nodes. One veterinarian felt the findings were consistent with lymphoma but acknowledged they could also represent IBD. He advised against a surgical biopsy because of my cat’s age and other health issues and felt the lymph nodes were too small for a reliable FNA. He recommended starting prednisolone.

The internist we originally saw to discuss radioactive iodine therapy for his hyperthyroidism and who noted the possible thickened intensities in the first place, recommended pursuing an FNA and before starting prednisolone to do an echo due to an expressed concern about using steroids because of his grade 2 heart murmur that the regular vet who has seen him for many years is almost positive is due to how long it took us to get his hyperthyroidism under control (which is now is).

I also consulted an oncologist, who noted that my cat does not have the classic symptoms of lymphoma and that the intestinal changes and reactive lymph nodes could be related to his other chronic conditions. She suggested that, if we wanted more information, an FNA of the mildly enlarged spleen with PARR testing could be considered. She also said watchful waiting was a reasonable option and, if this is lymphoma, she suspects it may be early small cell lymphoma.

So I’m receiving three different recommendations: pursue an FNA, start prednisolone and go from there, or simply monitor him. I'm aware starting prednisolone could build immunity to potential chemo options in the future, or cause CHF with his heart murmur. But don't want to sit on waiting and guessing to find out if this is worse. What they all agree on is not putting him through invasive full biopsy exploration.

He currently seems comfortable and is otherwise being treated for his existing conditions. So his regular vet says prednisolone won't hurt, start with that and wait, the oncologist says either test or wait and watch, and the internist says test but don't start anything.

If this were your cat, what would you do? Or what would you recommend?

Thanks.