Epidemiological and morphological analysis of feline injection site sarcomas

Feline injection site sarcomas (FISS) are malignant neoplasms of mesenchymal origin which arise in sites of injections in cats. The prevalence is estimated between 1 in 1000 and 1 in 10 000 vaccinations in the United Kingdom. The aim of this study was to estimate the incidence of FISS in Poland and to analyse clinical aspects and histological and cytological features of injection site sarcomas. In our study the prevalence of FISS was 0.16% (16 FISS on 10.000 of cats) in feline patients in one of a veterinary surgery which conducts the general practice and 85 on 10.000 cats in a practice focused on veterinary oncology. The most typical microscopic features of FISS found in the present analysis were: the presence of perilesional scarring and inflammation, aggregates of lymphocytes at the tumour periphery, moderate but usually marked cellular pleomorphism and intralesional necrosis. The most typical cytologic features of FISS found in present study were: the presence of neutrophils, marked cellular pleomorphism, the presence of lymphocytes and macrophages, the presence of extremely large nuclei in the neoplastic cells, and high sample cellularity.