Bump under skin on back leg- worried about injection site sarcomas

Three weeks ago I took my 5 year old kitty to the Vet to get his regular check up which included updates on his rabies and FIV. Two days ago I noticed  a lump on his back left leg about an inch across almost in the shape of an oval that is  underneath his skin/not attached to the skin. It's firm, seemingly painless (he doesn't react to me touching it), and I can't really move it around. I called the vet right away and am taking him in Saturday morning to see the doctor but wanted to see in the mean time if anyone has had any similar experiences? I had never heard anything about injection site sarcomas until I started to look online two nights ago and it made me feel sick to my stomach! Everything I'm seeing looks like bad news and i'm fearing the worst for my sweet boy

Injection site sarcoma's do occur, but are still pretty rare.  Try not to panic until you know for certain that this is what you are dealing with.  I've heard of these bumps appearing and taking over a month to go away, so maybe that's it.  No way for us to know.  BUT, if it happens to be the worst case scenario, that's why they give it to them in their leg... cats can do very well with only 3 legs .  Of course, we don't want that to happen, but if it does, he'll adapt...probably better than you. 

Hang in there.  Saturday will be here soon

Elise83 said:

 
Three weeks ago I took my 5 year old kitty to the Vet to get his regular check up which included updates on his rabies and FIV. Two days ago I noticed  a lump on his back left leg about an inch across almost in the shape of an oval that is  underneath his skin/not attached to the skin. It's firm, seemingly painless (he doesn't react to me touching it), and I can't really move it around. I called the vet right away and am taking him in Saturday morning to see the doctor but wanted to see in the mean time if anyone has had any similar experiences? I had never heard anything about injection site sarcomas until I started to look online two nights ago and it made me feel sick to my stomach! Everything I'm seeing looks like bad news and i'm fearing the worst for my sweet boy

Click to expand...

Injection site sarcomas take longer to form than a few weeks, generally, and its more likely just a reaction to the vaccine or an infection but the size of the swelling is a bit unusual for post vaccine swelling.  Good that you're taking him in.

It sounds like it could be his popliteal lymph node.  There are a lot of reasons this lymph node becomes enlarged, and cancer is only one of them.

http://www.cat-world.com.au/Cat-Health-Collection/swollen-lymph-nodes-in-cats.html

Injection Site Sarcoma (ISS) does not develop in several weeks, so I would relax a bit and tell myself that this is probably a reactive lymph node or injection site benign reactive nodule, both common when compared to the incidence of ISS which is approximately ! in 10.000.

Be careful in your measurement of the mass, as well, as a cat's skin/sub-Q soft tissue can measure a quarter inch or more in thickness and you're adding this skin dimension from two different aspects when your palpating the nodule between your fingers. A one inch nodule you're feeling may be a on-half inch nodule with an additional one-half in of skin/subcutaneous soft tissue.

Relax, take your boy to the Vet and assume it's going to be a benign post-vaccination site reactive nodule.

Good luck you both, and thanks for caring so much for your kitty-companion.

Elise83  - My cat, (Cootie) also has a lump about the size of a small olive, in the same area as you described - on BOTH legs. I took him to the Vet on Tuesday, 10/6 and a a biopsy was done on one of the lumps. I should receive the cytology report on Tuesday 10/3 when Cootie and I go back for follow-up. The vet said he had no idea what this is and especially on both legs. Cootie had Rabies and FVRCP shots one in each leg two years ago). He is 12.5 years old.

What is really odd, (at least to me), is that he is bright, perky and runs around playing like a kitten. He jumps up and down 3ft with no apparent problems. He eats heartily and is of normal weight and all of his labs are good, except the BUN at 55 and Creatinine 2.6, so he has Stage II CKD for which he gets a special diet.

I am very worried. But, I keep thinking, "What are the odds that sarcoma could be in both legs, in the same spot?", and "Why would he be so robust, if there are cancers that large?".  

So maybe our cats have something else???

Good luck to both of us! I will post when we get our results, and I am looking forward to see your's too.

Thank you everyone for all the kind words and thoughts..It really meant a lot to me! It's been a rough week with worrying about what this could be! The Vet gave me some good news that he thinks it might just be a reaction to the vaccines my kitty got 3 weeks ago. He said if it took 3 weeks for the this lump to develop I need to give it at least 3 more weeks to dissipate. He said he's been a vet for over 30 years and has only seen one injection site sarcoma which was about 15 years ago on an older cat. He said most vaccines now a days do not use the additives linked to a lot of the injection site sarcomas. My vet said if the lump hasn't gone away or gotten smaller in three weeks I'd need to bring Winston back in to re-evaluate but he seemed certain it would go away on its own. He said sometimes a cat's immune system will fight and wall off the vaccine and then it will need to be removed, but wouldn't indicate it is definitely cancer. He made a comparison of when we get a flu shot sometimes our arm hurts a lot and other times we don't feel a thing.. he said cats can have a reaction randomly and might never have it again. Thanks again to everyone posting.. It felt nice having some support  as I feared the worst!  I will be sure to update this if it doesn't go down and we have to have a second look at it.

desertstarlover said:

 
Elise83  - My cat, (Cootie) also has a lump about the size of a small olive, in the same area as you described - on BOTH legs. I took him to the Vet on Tuesday, 10/6 and a a biopsy was done on one of the lumps. I should receive the cytology report on Tuesday 10/3 when Cootie and I go back for follow-up. The vet said he had no idea what this is and especially on both legs. Cootie had Rabies and FVRCP shots one in each leg two years ago). He is 12.5 years old.

What is really odd, (at least to me), is that he is bright, perky and runs around playing like a kitten. He jumps up and down 3ft with no apparent problems. He eats heartily and is of normal weight and all of his labs are good, except the BUN at 55 and Creatinine 2.6, so he has Stage II CKD for which he gets a special diet.

I am very worried. But, I keep thinking, "What are the odds that sarcoma could be in both legs, in the same spot?", and "Why would he be so robust, if there are cancers that large?".  

So maybe our cats have something else???

Good luck to both of us! I will post when we get our results, and I am looking forward to see your's too.

Click to expand...

Hi Desertstarlover,

I'm so sorry to hear about your kitty!! I was so scared when I first felt the lump in Winston and he was also very energetic and didn't seem to be acting any differently so it was a little confusing. The good news is my Vet mentioned vets now a days typically don't use any vaccines that have the added stuff that's linked to the sarcomas the way they used to. Is your Kitty's lump hard? or soft? While I read online waiting to get into the vet this week I know I read a lot about fatty lumps appearing as cats get older which are really common and nothing to worry about. I know this site says something like "not if but WHEN you find a lump" http://healthypets.mercola.com/sites/healthypets/archive/2014/02/03/pet-bumps-lumps-treatment.aspx so hopefully your cat's are just from getting older! It's great you took him to the vet.. but I'm sorry you have to wait on results.  I know I was fearing the worst the whole time waiting to get some answers. Let me know how it turns out and I'll be sending prayers and good thoughts your way!

Elise83 said:

 
Hi Desertstarlover,

I'm so sorry to hear about your kitty!! I was so scared when I first felt the lump in Winston and he was also very energetic and didn't seem to be acting any differently so it was a little confusing. The good news is my Vet mentioned vets now a days typically don't use any vaccines that have the added stuff that's linked to the sarcomas the way they used to. Is your Kitty's lump hard? or soft? While I read online waiting to get into the vet this week I know I read a lot about fatty lumps appearing as cats get older which are really common and nothing to worry about. I know this site says something like "not if but WHEN you find a lump" http://healthypets.mercola.com/sites/healthypets/archive/2014/02/03/pet-bumps-lumps-treatment.aspx so hopefully your cat's are just from getting older! It's great you took him to the vet.. but I'm sorry you have to wait on results.  I know I was fearing the worst the whole time waiting to get some answers. Let me know how it turns out and I'll be sending prayers and good thoughts your way!

Click to expand...

Hi Elise83,

Thank you for your thoughts and prayers. All that good karma must have worked! Cootie's cytology report states "benign cutaneous reactive lymphoid aggregate". Lymph tissue is present and reactive, but that could be only from inflammation. I am to watch and wait and bring him back in three months. We are not completely out of the woods, because these needle aspiration/biopsies don't always pick up the 'bad' cells because such a small area is tested. However, I am going to try to stay positive, because it could have been a much worse result.

Cootie did receive the vaccination with the adjuvant, Defensor 3, which was then owned by Pfitzer, now Zoetis. It is still in use today and Banfield uses it. PurVax has a 3 year rabies vaccine, but you have to ask for it and it is expensive. I won't be vaccinating my two indoor cats ever again though, unless it is required of me to do so.