Vaccine-related sarcoma is a very malignant cancer which appears mostly in cats, although it has been documented in dogs and ferrets, as well. This condition is also known as vaccine-associated sarcoma (VAS), and a number of nations have set up task forces to monitor cases of vaccine-associated sarcoma, with the intent of determining the cause of the condition and possible preventative measures which could be used to reduce the likelihood of developing vaccine-related sarcoma.
The two vaccines most closely associated with vaccine-related sarcoma are the rabies vaccine and the feline leukemia virus (FeLV) vaccines. Typically the sarcoma appears within a few weeks of vaccination, in the form of a rapidly growing lump which may ulcerate through the skin. Vaccine-related sarcoma is infamous for being extremely fast-growing and aggressive, and it requires prompt action.
In a situation where a veterinarian suspects vaccine-related sarcoma may be present, a biopsy is taken, and the cat is scheduled for a lumpectomy to remove the sarcoma. If the biopsy comes back as positive for sarcoma, the surgery will go forward. Many vets excise well around the margins of the tumor, to ensure that it will not recur. Because sarcomas often appear near the spine, due to the placement of the vaccination site, some veterinarians prefer to recommend surgeons who are comfortable with working around the spine. After the sarcoma is removed, chemotherapy and radiation may be recommended to ensure that the sarcoma is eradicated.
This problem was first recognized in 1991, and it spurred a major reform of vaccination protocols for cats. Suspect ingredients in vaccines were also identified and outlawed to address the rise of vaccine-associated sarcoma. Veterinarians and cat owners are also encouraged to report cases of vaccine-related sarcoma for the purpose of generating as much data as possible.
The risk of vaccine-related sarcoma is real, but you should not let it stop you from vaccinating your cat. Discuss the feline vaccinations recommended for your pet with your veterinarian, and ask his or her opinion on the frequency of vaccination; some researchers suspect that the risk of vaccine-related sarcoma may be elevated by repeated vaccines. If your cat goes outdoors, vaccinating for FeLV and rabies is not optional. These diseases are horribly painful and unpleasant, and while vaccine-associated sarcoma can be deadly, the risk of infection with rabies or FeLV is not worth skipping a needed vaccine.