Cat Injection Site Sarcoma Welfare

Feline injection site sarcoma (FISS) is a rare but serious complication of injections that requires early detection and aggressive treatment.

Key Facts

FISS occurs at vaccine and other injection sites with an incidence of approximately 1 in 10,000 injections
The tumor is locally invasive and may metastasize requiring aggressive surgical treatment
Signs include a persistent lump at a prior injection site that grows or persists over 4 weeks
Vaccination site protocols have changed to reduce FISS risk through site rotation and limb injection
Early excision with wide margins is the most effective treatment - delayed treatment reduces outcomes

Welfare Considerations

FISS is rare but devastating when it occurs. Owner awareness of the signs and prompt veterinary assessment enables early diagnosis when treatment is most effective.

What You Can Do

Monitor vaccination and injection sites for any lump that persists or grows beyond 4 weeks
Report injection site lumps promptly to your vet - do not wait to see if they resolve
Support vaccine protocol changes that reduce FISS risk through limb injection