Thank you for your question.

When we see a lump in this region, we do have to be concerned and vigilant. We can see vaccine reactions, since we are putting a 'foreign material' under the skin for the immune system to address and this can lead to immune stimulation in the area and an associated lump. The can last a fortnight but usually will settle down with minimal treatment (antihistamines can settle these sooner).

As well, we can see abscesses if a stray skin bacteria managed to contamination the injection site at the time of vaccination. This usually leads to a pocket of infection/pus that tend to require antibiotics +/- draining if present.

Then there are the VAS you have mentioned. While this is a differential, they are not usually associated with an immediate appearance so soon after vaccination (usually they are associated with a months-years time line of presentation). That said, you are correct that they are aggressive tumors, but if they are removed quickly and completely (and this is the type of operation we tend to refer to the vet school's specialist surgeons rather do in practice), +/- radiation therapy, cats can survive this tumor type.

If a biopsy isn't an option, then I would strongly advise a fine needle aspirate (FNA) of the lump in this case. This is where the vet uses a needle and syringe to harvest cells from the mass. These cells are stained and they allow the vets to identify the nature of the mass. (If pus is retrieved, then infection is likely and can be addressed.) If your vet cannot identify the nature of the cells or in this cases where we just want to make sure this isn't a VAS, evaluation by a pathologist is strongly advised.

You have mentioned that the facilities in Oman might not be equal with the UK, but in the case of FNA samples (or even biopsy tissues) these can be sent to the UK for evaluation for clinical pathology and pathology professionals. Often it is a case of filling out the appropriate paperwork, but this is something the vet and the lab can help with. Both the labs at the Glasgow Vet School (HERE) and Bristol Vet School (HERE) do offer their services internationally, so while it may take a few days longer in the post there is no reason that the nature of the lump cannot be established even if you live outside the UK.

So, I would advise discussing antihistamine therapy to rule out a normal immune over stimulation from the vaccine. And do consider an FNA of the mass to know what it actually is. Because the sooner you know the identity of this abnormal growth, the sooner you can address the problem appropriately.

I hope this information is helpful.
Please let me know if you have any further questions.
Thank you,
Dr. B.

You are very welcome.
And I thank you for being so vigilant about this because all too often when these do arise people just don't appreciate that its best to check a lump sooner rather then later. (and nothing breaks my heart more as advanced disease that goes beyond being treatment responsive).

Our main things to watch for will be a change in size of this mass. We won't expect to see him showing any signs of illness (this is why silent masses can get so advanced before people see them as a problem). It will be difficult to note any changes on the cellular level at home, but you will want to monitor it for any swelling, growth, drop in its mobility when you handle it, or pain (or if he starts itching it more frequently and thus suggesting its growing enough to be stretching the skin).

At the end of the day, if your vet takes an FNA this will allow you to identify what this mass is and it will allow you to make an educated decision on what the appropriate next step is for him at that point. If it is a VAS, then you will know what options there are for this (and perhaps choose to see if there is a surgical referral practice in Oman). If its not a VAS or is a different type of mass (which then doesn't require that same aggressive surgery approach as the VAS) then you can take a sigh of relief and address it appropriately. It just will let us know what is actually afoot so that we can deal with it as effectively as possible.

And I do think this is the prudent choice for him. This is because if you go for surgery first and find that its a VAS afterwards, then surgical margins on the mass would have to be evaluated and there will be a chance that a follow up surgery to make sure all the margins are clear (since VAS removal requires much more aggressive resection of surrounding tissues then we would require with any other tumor type). So, knowing what it is will change the surgical approach and is another reason why identifying the mass pre-surgery is a good first step.

I wish you the best and do sincerely XXXXX XXXXX will find this is just an immune reaction from his immune system getting a bit overexcited by the vaccine.

All the best,
Dr. B.


41033.5247578704

You are very welcome.
No worries about the questions, I would much rather people had an idea of what might be ailing their pet and thus able to make educated decisions for them.

In my experience the VAS tend to come up as a single lump, tend to be quite adhered to the underlying tissues, and the vast majority were arising months to years after vaccination, which is why I do think we need to make sure we know what this is before jumping in, both from the nasty tumor side of things but also has to whether this is just the immune system being a bit over the top.

That said, we do always have to be vigilant since the number one rule of any cancer is to break the rules (otherwise we wouldn't have an abnormal growth in the first place). In regards XXXXX XXXXX types of tumors, we can also see tumors of the bone (osteosarcomas), cartiledge (chrondrosarcoma), muscle (rhabdomyomas), fat (liposarcomas), malignant fibrous histiocytoma, and undifferentiated sarcomas appear in this region (more often older cats). And while some of these are quite unfriendly in their own way, they don't all require such aggressive surgery as we'd use for the VAS.

The rate of growth varies significantly between the tumor types and individual tumors (since the malignancy can even be variable in the nasiest of tumors, like I said cancer defies rules). So, the main way to monitor growth would be to assess its size (in mm), write it down and see if this changes between assessment.

Honestly, while he is well within the time frame of having an immune response, if it seems to be enlarging and you are concerned, then I would say to have an FNA now (when the vet is open if its late there). That way, you don't have to fret about what it might be. You will be able to find out what it is and be able to take the next step.

You asked what I would do in this situation, and I can tell you that my wee cat in my icon had an oral mass last year. We knew it could be a nasty cancer or a polyp (and she is an old lady so we did worry that cancer was more likely), but the only way we would know what it was to know what the cells were up to. So, that is just what we did right after we found it. (our lucky miss had a polyp). But better then any speculation and suspicions and considering liklihood of what it could be, getting a sample of the cells can tell us what the mass is and therefore what we need to do.

So, for peace of mind and unraveling this wee mystery, have the FNA done sooner. And if it comes back as innocent immune stimulation, then you can have a sigh of relief and know its nothing to worry about. And if it sinister, then you will be able to address that as well.

All the best,
Dr. B.

PS- I know you have been doing a lot of reading but in case you missed the VAS information at Veterinary Partner, I thought I would pass it along (LINK)

Hello,

I am so glad to hear that they are reducing in size, and I agree that we would not expect that from a VAS or any of our main tumor based differentials. This does make it more suspicious that Snowy has perhaps had an overzealous immune reaction to this vaccine. I am glad to hear you are getting it checked out and I agree an FNA would be most appropriate before jumping into any surgery. That said, this is definitely a positive development with these lumps and hopefully they will continue to shrink until there is complete resolution.

All the best,
Dr. B.41041.4360353819