Cat Lump/Convenia/Sarcoma?
by Bitzy1977, Dec 20, 2011
Hi All,

Just over two weeks ago I took my little girl to the vets for an ear infection. We had a new kitten arriving the next day, so when the Vet asked us if we wanted to give our cat antibiotic tablets or a 12 day antibiotic injection (Convenia), the answer seemed simple!

Within two days of having the injection, she had developed a lump at the site of the injection, which was about the size of half an egg. We rushed her to the Vets and they suggested waiting for it to go down, as it could have been inflammation/reaction to the antibiotic injection. I didn't want to wait, as I had researched and found that VAS was common not only from vaccine injections, but from any kind of injection! *cries*... so we opted to have a biopsy done (just the cells).

The biopsy came back inconclusive, with a whole lot of detail that I didn't quite understand. All I can work out is that it states 'they can't rule out the possibility of sarcoma'...

It has now been just over two weeks since she received the injection and the lump has drastically reduced in size, and is now more like a hard pea. It has remained this size for approx 6 days now and is not decreasing or increasing in size.

As a precaution, the Vet has suggested having a biopsy done (where some flesh is taken), but from what I have read, they may as well just take the whole lump while they have her under anesthetic.

She is booked in to have this done tomorrow morning, but I am wondering if it is necessary?

Is it common for a sarcoma to reduce in size by itself?

I do not want to prolong the operation and find that in two weeks time it hasn't gone and I have possibly decreased her chance of survival because I waited!!!

Has anyone else had something similar to this? Should I just get it done anyway? Or is it uncommon for sarcomas to reduce in size by itself?


Here is what the test results said:

2 FNA smears from a subcutaneous mass on the dorsal neck

Low cellularity smears showing rare small clumps of spindle cells mixed with small amounts of dense bright eosinophilic matrix. Preservation of the spindle cells is suboptimal but those which are better preserved are
plump elongated cells with an ovoid nucleus, usually a single nucleolus and moderate amounts of deeply basophilic cytoplasm. Throughout the background is fresh blood with mixed leucocytes, in which eosinophils
are slightly overrepresented, with a modest amount of cell debris, and platelet clumps.

Mesenchymal cell proliferation, see comments

Cell harvest from the lesion was very low. Spindle cells are the predominant finding, the morphology of which resembles reactive fibroblasts, thus findings might reflect fibroplasia or granulation tissue. While spindle the cells exhibit little atypia, the possibility of a sarcoma cannot be excluded and should be borne in mind.

Eosinophils appear overrepresented although it is unclear whether these originate in the lesion or the contaminating peripheral blood. More definitive conclusions are not possible based on the few cells present,
and your clinical suspicions and the characteristics and behaviour of the lesion will be relevant in determining if excisional biopsy for histopathology is appropriate.

Dr Susan Boyd BVSc, CertSAM, MACVSc, Dip ACVP (Clin Path)
Veterinary Clinical Pathologist, Registered Specialist.
IDEXX Laboratories is a NATA accredited facility (Accreditation No.
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Member Comments (21)
by opus88Blank, Dec 20, 2011
hi...I was searching for my info on convenia and sorry I couldn't find it...but this one is just a terrible vac b/c it assaults the animal with such a high dose all at once and I've read it takes 6 weeks for it to clear from their systems so if there should be a reaction the poor animal is ill for 6 weeks or more...if pills are used at least if a reaction is noted than one can discontinue use.

first of all I'm NOT a Vet so what I tell you is just my opinion only....
I believe what your kitty has suffered is a reaction and inflammation can be a common reaction when the immune system becomes over loaded.

VAS is always a possibility of course but usually NOT immediately afterwards....any cancer takes awhile to develop.
Since the lump appeared immediately following the vac. IMO its a reaction, I can't believe a Vet would preform a biopsy based on what I've said...
AND since its already reducing in size where a sarcoma WOULDN'T than why the rush to preform yet another biopsy or lumpectomy?

If I were you Bitzy since its smaller and she is showing no other adverse effects than let it alone....give it some time, the lump IMO will probably disappear all together but if it doesn't with in a month or two THAN I'd be more concerned....but not yet.

keep us update, and best to you both....
by opus88Blank, Dec 20, 2011
I've been looking for the article I read but still haven't located it...did find this a facebook page that was started on the dangers of convenia...didn't read it all but perhaps you can find some info there.
I did find out it stays in the system a total of 65 its even longer than the 6 wks I quoted...I will post more info if I find it.
by Bitzy1977, Dec 20, 2011
Thank you for taking the time to reply. You have very similar thoughts and feelings as I do. I have been told in some cases that a sarcoma can develop in as little as 11 hours after injection, so that is my only concern. However, I can't ignore the fact that the lump has drastically reduced in size, which is the opposite of what any sarcoma does! Plus,l given what you have said about Convenia staying in the system for 65 days, it is possible that the lump/reaction may not decrease or disappear until it is out of her system completely.

I actually joined the Facebook page yesterday and posted my story there too. I was not aware of the dangers involved with Convenia and I feel obligated to spread the word on how dangerous it is. It is causing so many deaths and serious injuries to animals. I would never have opted for the injection had I been informed of the possible side effects.

I might take my cat to another vet tonight and get a second opinion. I would like to avoid such a big operation if I can, as she has been through enough already.

Again, thank you for your time. I really, really appreciate it. I will post updates as I go. I hope you have a wonderful Christmas xxx
by opus88Blank, Dec 20, 2011
I have never read that a sarcoma can develop that quickly....can I asked where you've read that info? interesting....its always possible with anything that weakens the immune system and IF an animal has a predisposition to cancer than perhaps that is always a possibility.

yes I would think it is possible that until the system has cleared anything that was toxic it wouldn't disappear totally. But again this is all just my opinion as a pet owner as yourself and not of a Vet...I am glad you are considering seeking a second opinion.

we follow what we think are good proven recommendations by our Vets...unfortunately they sometimes only believe what they are told by the drug manufacturers and alot of damage is suffered by our animals before they are willing to listen to reports.....not unlike our own doctors.

forgot to welcome you to our site, sorry its not under better circumstances, yes please keep us updated...and lets keep everyone aware of the dangers associated with this horrible drug.♥
by Bitzy1977, Dec 20, 2011
I have just tried to find the website/forum where it was stated, but I can't. It was a Vet who had responded to a lady going through a similar situation and she had basically said that she wasn't too worried about her cat, as the reaction was immediate after the injection. However, this Vet responded and said that to explain it in simple terms, that for a tumor to develop in the breast of a lady, where it is at a size that is detectable on a scan, would take approximately 4 years! However, he stated that it would only take 11 hours in a cat! This was very frightening to read!

To be honest, I am so glad you are not a Vet :) as it's some of the best advice I have read/received so far!

I will talk with my partner about getting a second opinion tonight.

If I thought 15 operations would fix it, I wouldn't hesitate. There is no limit for what I will do to help my baby. However, I also don't want to put her through a massive operation for no reason.

If I find the link to that site, I will post it. I've just been on 100's of different sites over the last week, I wouldn't even know where to start and try and find it.

Thanks for the welcome :) and I will be sure to post and update! <3
by opus88Blank, Dec 20, 2011
thank you and believe me I understand completely how you feel about your baby...we all do here. ♥
by Bitzy1977, Dec 21, 2011
Hello Opus88,

Last night I took Izzy to another vet for a second opinion. The Vet told me that no operation was necessary and that I just needed to monitor the lump over the next few weeks. She suspects that the injection was not given in the subcutaneous area, but much deeper in the muscle. That's where she could feel the base of the lump. The lump appears to have reduced in size again overnight, so fingers crossed this is looking very positive! However, if it hasn't gone in 2-4 weeks' time, she did suggest having a biopsy done.

I also asked about sarcomas and the chances of having one develop and then shrink in size... to which she responded 'would never happen'...

Part of me wonders why I have gone through all of this in the first place and why the other Vet just didn't tell me that. I understand that they are reluctant to commit to anything, but surely they have to be professionals at some point and guide us in a direction they think is best.

I have learned so much through this process and hopefully this will be the end of it and she won't have to have a biopsy done.

*fingers crossed* :)

If it wasn't for you and your guidance yesterday, I would never have thought to seek a second opinion. For that, I am forever grateful.

Thank you so much,
♥ Karen & Izzy
by Jade59Blank, Dec 21, 2011
Hi Karen, I've been following your posts and this is good news!  You must be very relieved.  Absolutely, fingers AND toes crossed for Izzy although I've been doing that all along :)  That second opinion makes perfect sense.  All I know about VAS is from a very long thread we have on this forum and from what I've read; right, the tumor NEVER shrinks.  I'm glad you found a vet who knew what she was talking about!  

Please continue to post updates on Izzy's condition.  I am so sorry for all you and Izzy have gone through, but glad you found MedHelp to add info on Convenia to our cat forum..something I'd never heard of and now, a word I will never forget!

by opus88Blank, Dec 21, 2011
GREAT NEWS....I am so glad you did get that second opinion too...can't imagine putting poor Izzy through yet another biopsy unless its absolutely warranted....what the second Vet said makes sense..
so lets hope and pray this lump will continue to shrink and this will be the last of this!!!!
You both have a MERRY CHRISTMAS, I'm so happy for this news...-)
I hope we'll hear more from both you and Izzy but under happier know we love to just chat or compare notes whenever...-)