Vaccine-associated sarcomas are uncommon, but when they do
occur, they can be aggressive and potentially difficult to
manage in cats. Although any cause for a local inflammatory
response—from an injection of any sort, including microchips—can
result in the formation of these types of sarcomas, they are all
typically classified as vaccine-associated. The American
Association of Feline Practitioners developed guidelines in 2006
for vaccine administration
(catvets.com/professionals/guidelines/publications). All
vaccines should be given subcutaneously, as intramuscular
administration may decrease the likelihood of early detection of
these masses. Nonadjuvanted vaccines should be used when
available, especially for rabies and feline leukemia virus
(FeLV), as these have been implicated in inflammation associated
with vaccine-associated sarcomas.1 The rabies vaccine should be
administered in the right pelvic limb below the stifle joint,
the FeLV vaccine in the left hindlimb below the stifle joint,
and the feline vir