Case Report of Feline Injection-Site Sarcoma(FISS) in a Five-Year-Old Persian Cat

<p><strong><span>Abstract</span></strong><span><br><br>This report examines vaccine-associated fibrosarcoma (FISS) in a five-year-old female Persian cat. This condition, primarily caused by chronic inflammatory reactions to injections, is recognized as a significant challenge in veterinary medicine. FISS typically develops at the site of vaccine or drug injections and is characterized by aggressive growth and a potential for metastasis.<br>The cat presented with a firm mass in the lumbar region. Examination and fine-needle aspiration biopsy were performed. Cytological findings revealed spindle to round cells with large oval nuclei, prominent nucleoli, and elongated cytoplasm with indistinct borders. Stromal fibers forming pseudo-aggregates were observed in the cellular environment, along with necrotic material. Some macrophages contained amorphous intracellular material, likely remnants of vaccine adjuvants or other injected products. The findings confirmed the presence of vaccine-associated fibrosarcoma in this cat. Although the tumor is primarily localized, metastasis to the lungs and lymph nodes is possible; however, thoracic radiographs showed no evidence of metastasis.<br>The mass was surgically excised with wide margins. Despite the recommendation for radiotherapy to minimize recurrence risk, the owner's financial constraints prevented this approach. Local tumor recurrence is common in FISS, and successful treatment depends on achieving adequate surgical margins and complementary therapies.<br>This study highlights the importance of modifying vaccination strategies, such as using adjuvant-free or recombinant vaccines and selecting appropriate injection sites, such as limb extremities. Treatment management includes surgery, radiotherapy, and continuous follow-up. Educating veterinarians and pet owners plays a crucial role in reducing the incidence and managing FISS effectively.<br><br></span><strong><span>Keywords:</span></strong><span> fibrosarcoma, vaccine, cytology, FNA,FISS.</span></p>