Before you read this month’s mystery, I want to emphasize how vitally important it is that we all continue to vaccinate our cats for diseases that can be deadly. If we don’t, we will certainly see some terrible health implications for our beloved pets. After you read the story about Coby, I will explain the difference between the cat vaccines that we use in our clinic and the ones that have been identified to potentially cause issues.
Coby came to see me because he had a very large swelling on his front leg that extended from his shoulder all the way down to his paw. It was not impacting his stride but the owners knew it had to be a problem. When I examined Coby, he seemed to not even notice there was a problem as he continued to act and walk normally.
Before we scheduled surgery to remove as much of the lump as possible, we had to do the necessary pre-operative testing. This includes bloodwork to check for any metabolic abnormalities and Xrays to make sure there has been no spread of disease elsewhere in the body. Coby passed with flying colors.
In surgery, I removed as much of the mass as possible. Since it was all along his leg, I had to be careful to retain enough tissue to close the wound. While Coby was home recovering, we had to wait patiently for the pathology results.
The mass turned out to be an injection-site sarcoma, meaning that a tumor most likely developed because of a vaccine that had been given at some point over Coby’s lifetime. This can happen shortly after a vaccine is given or several years after the fact. I hadn’t seen Coby for any vaccine visits, so it clearly was a vaccine given elsewhere. There is no way to tell which vaccine caused his problem, however, as part of a feline-specific veterinary community, we know the likely culprits.
The history of vaccines
Before the 1980s we didn’t see many of these tumors develop in response to animal vaccines. But things changed when the vaccine manufacturers began adding substances called adjuvants to their vaccines with the intent of enhancing the immune response. This is when we started to see tumors develop, especially in cats.
Injection-site sarcomas are not easy tumors to deal with. To the naked eye, the tumor looks like a solitary mass, but we as veterinarians know, they act like tentacles, and the cancer cells can reach farther and wider than anticipated. In order to eradicate the tumor, it is typically necessary to perform drastically wide and deep excisions, which in some cases is not feasible depending on the tumor’s location. They can require radiation as well and even in the best of circumstances, these tumors usually come back, and are harder to eradicate, with each recurrence.
How to protect your cat
In response to this issue, there are now vaccine companies that are manufacturing vaccines for cats that are completely free of adjuvants to minimize these tumors from developing. To the best of my knowledge, there has not been a case of these injection-site tumors in cats who have only received these non-adjuvanted vaccines, and the non-adjuvant types are the only kind of vaccine I will carry in my practice.
It’s important to ask your veterinarian specifically if they are giving your cat a vaccine with adjuvants and it is prudent to stay away from those that contain these substances. There are theories that the cats who develop these tumors have to be genetically predisposed to do so and it is also theorized that any injection can cause an aberrant immune response.
It is vitally important to continue to vaccinate our cats for diseases that can be deadly. Please email us with any questions regarding the difference between vaccines and to know which ones your cat is receiving.
The happy ending
Getting back to Coby, he is doing wonderfully since his surgery. The site has healed beautifully, and I hope that it will be years before the vaccine-sarcoma recurs.