Research overview: feline injection-site sarcoma

In the early 1990s, clinicians and pathologists recognized an association between vaccination, particularly certain adjuvanted vaccines, and the development of aggressive soft-tissue sarcomas at injection sites in cats, a finding that profoundly influenced feline vaccination practice. Investigation implicated chronic inflammation at the injection site as a driver of malignant transformation in susceptible cats. This overview synthesizes the oncology and epidemiology literature rather than one source, describing how the association was identified, why it prompted changes such as standardized injection-site locations to aid surgical management, reduced unnecessary vaccination, and development of non-adjuvanted vaccines, and how the entity is now termed feline injection-site sarcoma to reflect that other injectables may contribute. It matters because it reshaped how and where cats are vaccinated worldwide.