Felis ISSN 2398-2950

Injection-site associated sarcoma

Synonym(s): Post-vaccinational sarcoma, FISS

Contributor(s): Laura Garrett, Irene Rochlitz, David Scarff, Isabelle Desmas-Bazelle, Jane Dobson


  • First reported early 1990's Suspected adverse reactions to vaccination.
  • Low incidence (relative to number of vaccinations performed).
  • Cause: tumor develops at site used for injection, most often vaccination (microchip implantation or injection of diverse array of drugs have also been reported as a cause).
  • Signs: firm soft tissue swelling usually between scapulae, locally aggressive.
  • Diagnosis: histopathology.
  • Treatment: surgical excision with wide margins. Adjuvant radiation therapy or chemotherapy may be indicated in some cases.
  • Prognosis: guarded.
    Print off the owner factsheet Feline injection site sarcoma Feline injection site sarcoma to give to your client.
Clinical tip:
Question: The Vaccine-associated Feline Sarcoma Taskforce recommends surgery if the mass is greater than a certain size. What is this size?
Answer:  Excision when mass is greater than 2 cm in diameter.



  • Related to post-injection inflammatory reactions. Vaccines that contain aluminum as an adjuvant have been proposed to be more likely to trigger a vaccine site reaction (although post-vaccinal sarcomas have also occured after non-aluminum adjuvanted vaccines and large epidemiologic studies did not show that aluminium-containing vaccines pose a greater risk).
  • Increase in risk with increasing number of vaccines administered at same location.
  • Both FeLV Feline leukemia virus disease and rabies Rabies vaccines have been associated with increased risk of developing sarcoma at site of vaccination Suspected adverse reactions to vaccination.
  • No single vaccine manufacturer or type of vaccine has been shown to pose a greater risk.
  • No particular vaccine practices (needle gauge, shaking vials, mixing vaccines in one syringe) have been shown to pose a greater risk.


  • Vaccination against rabies or FeLV.


  • Tumor develops from 4 weeks to 10 years after vaccination.


This article is available in full to registered subscribers

Sign up now to purchase a 30 day trial, or Login


This article is available in full to registered subscribers

Sign up now to purchase a 30 day trial, or Login


This article is available in full to registered subscribers

Sign up now to purchase a 30 day trial, or Login


This article is available in full to registered subscribers

Sign up now to purchase a 30 day trial, or Login

Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Hartmann K, Day M J, Thiry E et al (2015) Feline injection-site sarcoma: ABCD guidelines on prevention and management. J Feline Med Surg 17 (7), 606-613 PubMed.
  • Ladlow J (2013) Injection site-associated sarcoma in the cat: treatment recommendations and results to date. J Feline Med Surg 15 (5), 409-418 PubMed.
  • Martano M, Morello E, Buracco P (2011) Feline injection-site sarcomas: past, present and future perspectives. Vet J 188 (2), 136-141 PubMed.
  • Phelps H A, Kuntz C A, Milner R J et al (2011) Radical excision with five-centimeter margins for treatment of feline injection-site sarcomas: 91 cases (1998-2002). JAVMA 239 (1), 97-106 PubMed.
  • Séguin B (2002) Feline injection site sarcomas. Vet Clin North Am Small Anim Pract 32 (4), 983-995 PubMed.
  • Hershey A E, Sorenmo K U, Hendrick M J et al (2000) Prognosis for presumed feline vaccine-associated sarcoma after excision - 61 cases (1986-1996). J Am Vet Med Assoc 216 (1), 58-61 PubMed.
  • Brearley M J (1999) Vaccine-associated sarcoma-an emerging problem. J Feline Med Surg​ (1), 5-6 PubMed.
  • Macy D W (1999) Current understanding of vaccination-site associated sarcomas in the cat. J Feline Med Surg (1), 15-21 PubMed.
  • Esplin D G, McGill L D, Meininger A C et al (1993) Post-vaccination Sarcomas in cats. JAVMA 202 (8), 1245-1247 VetMedResource.

Other sources of information

  • Withrow S J, Vail D M, Page R L (2013) Small Animal Clinical Oncology. 5th edn. Elsevier.
  • Ogilvie G K & Moora A S (1995) Managing the Veterinary cancer patient: A practice manual. Veterinary learning systems. pp515-518.
  • Kass P H, Barnes Jr W G, Spangler W L et al (1993) Epidemiologic evidence for a causal relation between vaccination and fibrosarcoma tumourigenesis in cats. JAVMA 203, 396-405.
  • Macey D W (1994)Vaccine associated sarcomas. In: Proceedings of the 12th Annual American College of Veterinary Internal Medicine Forum, San Francisco, GA.pp 854-856.