Description of a Feline Injection-Site Fibrosarcoma with Metastasis in the Cerebellum

Feline injection-site sarcomas were initially described by Hendrick and Goldschmidt (1991). The link between vaccination site and sarcoma occurrence suggested the term of vaccine-associated sarcomas. Our paper describes an unusual feline injection-site fibrosarcoma with cerebellar metastasis. A 7-year-old female domestic short-hair cat was submitted to the Pathology Department (Faculty of Veterinary Medicine Cluj- Napoca, Romania) for necropsy. A subcutaneous tumor (relapse) in the interscapular region and multiple metastatic masses in the lungs, kidneys, subcutaneous tissue (scapular and thigh regions) and cerebellum were observed. Cytological, histological and immunohistochemical (for vimentin, desmin, multi-cytokeratin, α-smooth muscle actin, S100 and CD45) analyses from all tumors were performed. Cytological examination identifi ed highly pleomorphic spindle-shaped cells admixed with neoplastic multinucleated giant cells. Histologically, all neoplastic masses were composed of numerous spindle cells arranged into interlacing bundles. Extensive intratumoral areas of necrosis along with a neutrophilic infiltrate were also detected. A fibrillary material was present among neoplastic cells (green stained by Masson’s trichrome method), suggesting a collagenous structure. In all tumors assessed, immunohistochemistry showed an intense reaction only for vimentin in numerous neoplastic cells. Based on the history, gross, cytological, histological and immunohistochemical data, the final diagnosis was recurrent feline injection-site fibrosarcoma, with multiple metastases (including in the cerebellum). Overall, an uncommon case of feline injection-site fibrosarcoma has been reported. This is the first consistent record of an injection site sarcoma in a cat with cerebellar metastasis.