Comparison of fibrosarcomas that developed at vaccination sites and at nonvaccination sites in cats: 239 cases (1991–1992)

Abstract

Summary Questionnaires were sent to veterinarians who had submitted a fibrosarcoma from a cat to the surgical pathology services of the veterinary schools of the University of Pennsylvania and Tufts University between Jan 1, 1991 and June 30, 1992. Questionnaire items included signalment, FeLV and feline immunodeficiency virus status, site of sarcoma, vaccination site, vaccines used, treatment, biologic behavior of the tumor, and final outcome. Data were analyzed, using Student’s t-test for continuous data, χ2 test for categoric data, and log-rank test for survival estimates. Comparing results for cats with vaccination-site (vs) tumors and nonvaccination-site (nvs) tumors, we determined that vs tumors developed in younger cats and were larger than nvs tumors. Although vs sarcomas were biologically aggressive and redeveloped more often than nvs sarcomas, metastasis was not detected, and cats with vs tumors survived longer than cats with nvs tumors. Vaccination-site sarcomas developed in cats after injection of many types of vaccines, administered singularly or in combination. Of the cats in the vs group administered a single vaccine, 37% were given rabies, 33% were given feline viral rhinotracheitis/calicivirus/panleuhopenia virus, and 30% were given FeLV vaccines. Cats with vs tumors were more likely to have received FeLV vaccine and less likely to have received rabies vaccine than those with nvs tumors. Although vaccines produced by certain manufacturers were used most often in cats with vs and nvs sarcomas, it was believed that this probably represented marketing practices and brand popularity. Many of the vaccines used had aluminum and other highly immunogenic adjuvants. We hypothesized that resident fibroblasts and myofibroblasts proliferated in the cats in response to injected adjuvants or other vaccine components, and, in some cats, these cells eventually underwent neoplastic transformation.