Squamous cell carcinoma is the most common oral tumor in cats. The risk of developing oral squamous cell carcinoma increases more than 3.5-fold with the use of flea collars and high intake of either canned food in general or canned tuna fish specifically. Exposure to household tobacco smoke increases the risk of oral squamous cell carcinoma 2-fold in cats. Squamous cell carcinoma frequently invades bone, and the degree of invasion is usually severe and extensive. Paraneoplastic hypercalcemia has been previously reported in cats with oral squamous cell carcinoma. The metastatic rate in the cat is unknown. However, oral squamous cell carcinomas in cats have a very poor long-term prognosis as animals most often succumb to local disease.