Fibrosarcomas at Presumed Sites of Injection in Dogs: Characteristics and Comparison with Non-vaccination Site Fibrosarcomas and Feline

Fifteen fibrosarcomas, surgically excised from presumed sites of injection in dogs, and 10 canine fibrosarcomas excised from sites not used for injection were histologically and immuno-histochemically compared with 20 feline post-vaccinal fibro-sarcomas. Canine fibrosarcomas from presumed injection sites were of grade I (3), of grade II (4) and grade III (8). Two fibrosarcomas from non-injection sites were of grade I, four of grade II and four of grade III. Feline samples were classified as grade I (2), grade II (4) and grade III (14). All fibrosarcomas from presumed injection sites of both species showed lympho-cytic inflammatory infiltration located at the tumour periph-ery, while two canine fibrosarcomas from non-injection sites showed perivascular inflammatory infiltration within the neo-plasm. All samples were immunohistochemically examined for vimentin, smooth muscle actin, muscle specific actin and des-min expression. All tumours were positive for vimentin. Ten canine fibrosarcomas from presumed injection sites and all feline samples contained cells consistent with a myofibroblastic immunophenotype. Aluminium deposits were detected in eight canine fibrosarcomas from presumed injection sites and 11 feline post-vaccinal fibrosarcomas by the aurintricarboxylic acid method. The present study identifies distinct similarities between canine fibrosarcomas from presumed injection sites and feline post-vaccinal fibrosarcomas, suggesting the possi-bility of the development of post-injection sarcomas not only in cats, but also in dogs