Vet med peeps...a ?

Aside from a biopsy, is there a way to tell the difference between bony cancers in the forelimb (osteo-, cohondro-, fibrosarcomas)? Does it matter, really?

My "medical weirdo" of a dog is going in to the vet tomorrow, and I am more than a bit worried the vet will suspect bone tumor, which we will then end up getting an Xray for.Which, I suppose I am okay with.

Now, this dog has been a freak of nature from day one, and there's been MULTIPLE times where everyone (specialists included) SWORE up and down he was the textbook case of something (lymphoma, for one; another form of cancer for two, etc etc)...and then it wasn't (or the reverse: "Sure, we can test his X,Y, or Z, but that's CERTAINLY not it." oops...I guess it is.). So, I'm well aware of the "well, don't get yoru panties in a twit yet b/c if it looks and walks and quacks like a duck (and has $5000 in tests and surgeries suggesting it SHOULD be a duck), it could still be an elephant" phenomenon...but...

He (the dog, not the vet) has a history of lipomas--both standard fatty ones, and invasive ones (inlcuding one in his orbital socket (one of the duck that wasn't a duck instances), his thigh, and on his ribs). So I know what they are like, in all their forms. But in January, I noticed his right wrist was swelling a bit, although he didn't really favor it, unless you squeezed it. Because he's elderly (12.5), because he has a history of lipomas, and b/c he also has a history of joint pain, I've just monitored it. It has slowly grown in size, not a ton, but maybe a cm in circumference. It is NOT soft, malleable, pliable, or moveable in anyway. It is bony and rigid. And painful to the touch.

As of last week, he now limps on a rear leg (the one with the invasive lipoma and a dysplastic hip) AND the front leg. So, into the vet we go. Where I know I will end up on the horns of a dilemma.

I can probably swing limb XRays...and MAYBE chest films to check for mets, but that's about it. My husband would have a CORONARY if we spend anymore on vet bills--and those two are about all I can afford out of pocket.

I know the treatment options for osteosarcoma...what I don't know is where (if this really is, god forbid, cancer) do you draw the line, and how much testing do you do if it isn't? (meaning, do you keep looking for causes, and keep feedining him rimadyl?)

He has a moderate heart murmur (it has progressed in the last two years) and low thyroid (on meds). He has the lipomas and the dysplasia. he also has an autoimmune condition called sebaceous adenitis (which, while really ugly and cosmetically bad, aside from some mild skin infections from time to time, doesn't bother him). But he is happy and healthy (all things considered). OTOH, he is almost 13, and a large breed dog (he's an 1/2 akita; the other half is a GSD/Dobie cross).So, even in tip-top shape, it's not like he's a 5 year old adolescent with a decade in front of him.

Amputation/chemo would get you a couple months, even on a healthy young dog. Amputation alone gets you not much more than pain relief (but wouldn't help, as his back leg probably couldn't handle the strain). Radiation for pain management? Keep looking for the cause? AHHHHH!

I know all the options, and I can make a pretty good guess what this will be (but again...we, and way smarter people than me, have been wrong before), but I'm just not sure how fine of a line to walk.

Sorry, this has been super long, and I don't have a question per se... I think I just needed to think out loud. I suppose the best thing to do is to see what happens. :D Sorry for t he public exposure to my random brain waves! :p