Feline oral squamous cell carcinomas (SCCs) account for approximately 10% of all feline tumors. Cats will often have mucosal ulceration and bone necrosis that is painful and interferes with eating and drinking. Cats with these devastating tumors are often euthanized with progression of local disease. The historical failure of treatment of this disease with surgery, chemotherapy, or radiation therapy discourages owners and veterinarians from pursuing treatment. This project will evaluate archived tissue biopsy samples from oral SCCs using immunohistochemistry. Several factors will be analyzed to help characterize the behavior of these tumors. This information can be used to develop more effective treatment protocols using radiation or chemotherapy. There is also the potential for use on pre-treatment biopsies as predictive assays. This will help develop more effective treatment protocols based on tumor biology.