A 13-year-old male castrated domestic longhaired cat was presented to the Cornell University Hospital for Animals Oncology Service with a chief complaint a subcutaneous mass over the left hip. The mass was first noted six months previously and was initially slow growing. In the two months prior to presentation, the mass rapidly grew, becoming multi-lobulated, ulcerative, and hemorrhagic. Minimum database, imaging, and biopsy results were consistent with a diagnosis of injection site sarcoma. This paper will review feline injection site sarcomas with an emphasis on treatment principles, prognosis, and recommendations for general practitioners.