Epulis is the most common type of benign or non-cancerous tumor in dog's mouth. A benign tumor is one that does not spread to other parts of the body. However, an epulis can be "locally invasive," which means that it can grow into the tissues surrounding its initial location. This tumor of the periodontal ligament, which is the structure that holds the dog's tooth in place. Epulides are the most common benign oral tumors in dogs; cats rarely have benign oral tumors. These tumors occur in dogs of any age, but they are generally found in middle-age dogs over six years old.

Epulides have three types and are recognized, grouped by tissue origin. The first is Fibromatous Epulis, they are pedunculated (on a stalk or stem) and non-ulcerating (no interruptions on the outside of the growth). Fibromatous is the most common non-cancerous oral tumor of dogs. These firm, pink tumors arise from the gums. Even a non-cancerous, Fibromatous may become quite large and completely envelop one or more teeth. also may not be possible to tell whether an oral tumor is an epulis or one of the less common, malignant tumors that may occur in the mouth. These growths may become inflamed and ulcerated, causing pain on chewing. They are most common in dogs over 8 years of age.

Other types of Epulis are Ossifying Epulis and Acanthomatous Epulis. Ossifying Epulis includes fibruous tissue and also contains bone cells and these may transform into a cancerous tumors. Ossifying has a greater abundance of hard tissue, osteoid, bone and cementum than fibromatous epulides. Fibromatous and ossifying epulides are now considered to be peripheral odontogenic fibromas, while Acanthomatous epulis is now called canine peripheral ameloblastoma or canine acanthomatous ameloblastoma. Acanthomatous (also called Oral Adamantinoma) is a locally invasive, sometimes recurrent, tumor of the gums of dogs and sometimes cats. These routinely aggressively invade local tissues including bone and they generally do not metastasize, but due to their locally aggressive nature surgical excision must include a full 1-cm margin of clinically normal tissue to prevent recurrence.

An epulis is usually first noticed as a growth on the gum line of the dog's mouth. In rare cases, teeth may be moved from their normal position because of the growth of the epulis. Your pet is initially unaffected by the epulis. However, if the growth becomes large, it could bleed, cause problems with eating, or affect the teeth or jawbone. An epulis is treated by surgically removing it, including a broad margin around the growth. Sometimes, especially with larger tumors, teeth adjacent to the epulis have to be removed. In other cases, portions of the jawbone may need to be removed to cure the condition, for if a portion remains, it will often regrow. Radiation treatment is sometimes used in addition to or instead of surgery for treating large tumors. The prognosis is good if the entire epulis can be removed, so it's best to avoid delay of surgery that would allow the epulis to grow. After surgical removal, the prognosis can be very good depending on the type of epulis removed. A subtype of epulis called an "acanthomatous" epulis can cause more bone problems than the other types, and can be more difficult to completely remove.