Mass on my cat's wrist area.

About a month ago, my boyfriend mentioned to me that my almost 9 year old cat Maggie was lifting her left paw up while sitting. I palpated both of her forelimbs completely and manipulated their movements but found nothing significant so I wrote it off as some weird behavior. Fast forward to a couple days ago. Maggie was sitting on my desk in front of me, lifting her left paw as she had started doing previously. I watched her do it. She finally put the paw down and put a little bit of weight on it and i noticed an enlargement. On palpation, her left wrist is thicker and stiffer with more prominent bone protrusions than her right. I immediately scheduled her to be seen at my vet, which was today. The vet took 2 x rays and after looking at them, stated she did appear to have more bone on her left distal radius/ulna (wrist) than on her right, but because she is not limping, it may just be an old injury. He told me to come back if it got worse. As far as I know, Maggie has never had an injury to any of her legs. She used to sit on that leg and curl it under her sometimes. Now she won't sit on it very long and she won't curl it under her. I am contemplating seeking another opinion but I don't want to be charged $300 and told to come back if it gets worse. I am attaching the xrays because I feel that there is definitely something going on with the left wrist, you can see a swelling/shadow type mass around it in the first xray. I don't know why there would be swelling with no injury. My questions for you guys are 1. Have you ever dealt with bone tumors in your pets? If so, how long did it take for them to develop? 2. Do you think I should seek a second opinion or wait and see if it gets worse? I am worried because when I initially palpated her limbs I didn't notice anything different between them, and now there is an obvious difference in such a short time. If it ends up being a growth, wouldn't it be ideal to catch it as early as possible? My boyfriend thinks I am overreacting but I have a very bad feeling something is wrong.

I can't evaluate the x-rays but I do agree with you that it's worth seeking out a second opinion, if only because it would reassure you.  That's worth something in and of itself.  However, you are obviously very in tune with Maggie and it's hard to believe you would have missed an earlier injury severe enough to cause this kind of thickening.   I also think you're right to be concerned that the swelling increased so much over such a relatively short period of time.  I'm not sure why it would cost you $300 to get a second opinion though.  Are you thinking the second vet would have to retake the x-rays?  It seems you should be able to take Maggie to a second vet to have her examined and to have that vet evaluate the x-rays for you.  

It might be helpful for you to find a vet who specializes in cats, if there is one in your area.

And, btw, welcome to TCS! 

Hi, and welcome!  I completely agree with @Margd  .  Something is obviously wrong with the left "wrist" area.  Another vet can read those same x-rays, and taking Maggie to a cat specialist is an excellent idea if there is one in your area.  I would definitely take her to another vet for a second opinion.  I don't have personal experience with bone tumors in cats but I do have experience with cat cancer.  You are NOT overreacting.  Maggie needs help.  Trust your instincts where she's concerned.  I wish you and Maggie the best.  Please let us know how this goes.  Hugs........ I know you are very concerned.  I would be too.