In general, oral tumors in dogs are more likely to be benign than malignant (malignant = cancer). In cats, oral tumors are much less common, but usually are malignant. However, for an individual oral tumor, there is no way to be certain if it is benign or malignant without a biopsy. Oral tumors that are large or rapid-growing are more suspicious of oral cancer. If an oral tumor is benign, the 2 most common benign tumors in dogs are peripheral odontogenic fibroma (POF) and canine acanthomatous ameloblastoma (CAA). These types of tumors are not malignant, so they do not spread to distant sites. These are benign tumors, but they can be locally invasive (especially CAA) and are prone to recurrence if they are not removed completely. For cancerous tumors, the treatment will depend upon the type, location, and size of the tumor. When an oral tumor is suspected to be cancerous, it is often best to take a sample of the tumor (biopsy) to find out what type of tumor it is, before pursuing aggressive surgery. Treatment decisions should be based on the expected behavior of the tumor. For cancerous tumors, referral to a veterinary oncologist (cancer specialist) may be recommended.