Does anyone know if presence of a clear yellow fluid can be universally interpreted as a cardiological condition, or can there be some other condition that could cause that?

The cat was at the vet on Monday, was feeling a little better yesterday, but today he seems to be deteriorating and appears to have fluid building up again. When I picked the cat up after they drained him, the vet sort of mentioned in passing that there could be cancer involved as well.
I suppose that I'm in denial about this, and am hoping that the vet might have overlooked something or mis-diagnosed the symptoms, and so I hope you understand my despration.

My beloved Rocky may not make it till Friday. I'm beside myself.
Does anyone know if presence of a clear yellow fluid can be universally interpreted as a cardiological condition, or can ... and so I hope you understand my despration. My beloved Rocky may not make it till Friday. I'm beside myself.

I would certainly get a second opinion. Not all heart problems are hopeless. There are other conditions as well that cause fluid build up. It doesn't sound good, but I'd sure call and get in with someone else tomorrow. I hope for the best. My thoughts are with you.
Karen
You've given this cat 5 years he never would have had. Felv is only a matter of time and 5 years is a long time for those with it. Yellow fluid can also be a F.I.P. which is a form of cancer. I'd just keep him as comfortable as you can for the time he has left. It could be days or weeks but I don't think he's going to recover.