Cat Feline Injection-Site Sarcoma: Prevention and Treatment

Injection-site sarcomas are rare but aggressive tumors in cats requiring rapid diagnosis and wide surgical excision for best outcomes.

Key Facts

Feline injection-site sarcoma occurs at a rate of approximately 1-4 per 10,000 vaccine administrations
The risk is higher with FeLV and rabies vaccines containing adjuvants than non-adjuvanted products
Tumors typically appear 3 weeks to 3 years after injection at the site of administration
WHO recommends administering vaccines as distally as possible on limbs to enable complete excision if tumor develops
A lump persisting more than 3 months, larger than 2 cm, or growing after 4 weeks warrants biopsy
Treatment requires wide surgical excision (3-5 cm margins) often with radiation therapy
The prognosis is poor for many cases - median survival after surgery and radiation is approximately 19-24 months

Welfare Considerations

Injection-site sarcomas cause local invasion and rapid spread, causing pain and progressive disability if not caught early. Wide excision including amputation when limbs are affected is the most effective welfare intervention providing the longest disease-free period. Delayed diagnosis after a lump is noticed leads to smaller surgical margins and higher recurrence rates - early biopsy of persistent lumps is a welfare-critical decision. Vaccine benefit still outweighs the low sarcoma risk for essential vaccines.

What You Can Do

Check vaccine injection sites monthly for lumps persisting after 1 month post-vaccination
Seek biopsy of any lump that grows, persists more than 3 months, or exceeds 2 cm at injection sites
Request vaccination in the distal limb following WHO guidelines rather than interscapular region
Discuss which vaccines are essential for your cat's lifestyle to avoid unnecessary injections
Accept amputation as a compassionate and effective treatment when sarcoma occurs on a limb
Support research into non-adjuvanted vaccine formulations that may reduce sarcoma risk