My cat has a growing lump after vaccination. Could it be sarcoma?

Normally, there will be a small bump where a vaccination is given and this can persist for several weeks to months. If it persists for longer than 3 months and / or continues to grow in size, I would recommend having a veterinarian examine Simba so that the most appropriate diagnostic and treatment recommendation can be made. Sometimes, vaccines can cause cancerous tumors to grow in the area where the vaccine was administered. This is less common now, but still a risk. I hope this helps! Please let me know if you have any further questions / concerns and I would be more than happy to help you further.

It does need to be noted with your vet to verify if it is a vaccine reaction. Cats can have injection induced sarcomas which are cancer and require surgery. The general rule is if it is there longer than 3 months or gets larger, then surgery is warranted, otherwise they go away on their own I would have them document the vaccine site and the size for proper monitoring in the future.

Great question! This lump could be a localized reaction to the vaccine if the lump is in the area where the vaccine was given. Other options could be a cyst or a benign tumor. Given it's not painful and if she is otherwise acting normally, this isn't an emergency. Keep an eye on this lump, and if it doesn't go down over the next couple of days or gets bigger, then I would have Poppy seen by a vet. Good luck, I hope this helps!

I am sorry to hear about Knox. I would ask for a second opinion on the original aspirate. If it was not sent to a pathologist, it should be sent for a pathology review. If a pathologist did review the original slide, your vet can request that the slide be reviewed again by another pathologist. If the area is still suspect or you are concerned, you can have the mass removed and have a biopsy done to confirm the diagnosis.

Cats typically do not receive vaccines on their belly, they are given over the shoulders on their back; therefore, I do not think this mass you felt is due to her vaccines. It could be that Lucy has a benign tumor, cyst, abscess, or a malignant tumor (unlikely in a young cat) causing the lump, and I would have her seen by a vet for it. The vet can examine and diagnose it, and let you know if any treatment is needed.

I would recommend to get Peanut in sooner rather than later to have the mass aspirated. This should give you an idea of what type of mass it is and if you need to be worried. Most skin masses are benign but there is always a chance its cancerous. The aspirate is quick and generally does not require sedation or stitches. Try not to worry until you know what you are dealing with. Best of luck with Peanut.

Hello and welcome to Petco Pet Education Center, formerly Petcoach. Soft masses that are part of the skin can be either abscesses (pockets of infection), small bits of swelling from vaccine injections (these can last a few months sometimes), fatty masses, and less commonly in a 4 month old kitten, cancers. I would monitor it, if Bean is painful or if it is growing or changing get it looked at right away, otherwise just monitor for now and have it assessed by your vet next time you are in. Best of luck with Bean!