Fibrous epulis (gingival hyperplasia) in a horse.

Epulis is the generic and clinical term for tumor-like masses on the gingiva, including hyperplastic as well as neoplastic lesions. Fibrous epulis is uncommon in horses, and its rarity has induced us to write this case report.A 18-year-old Italian saddle horse gelding was referred for examination and surgical treatment of an intraoral peduncolated mass of 5 cm in diameter, located in the mucosa in the vestibular portion of the incisor bone of the upper jaw. The radiographic examination excluded any bone involvement. Six months after surgical removal, there was no recurrency development. The mass was firm, smooth and grey-pink in colour and connected to the gingiva with a peduncle of fibrous tissue. Histologically, an intact multilayered squamous epithelium bordered well vascularized fibrous connective tissue with only a few foci of inflammatory cells. Squamous epithelium formed long fronds originatig from the surface, which assumed a net shape if trasversally sectioned. The mass showed moderately dense cellularity represented by small stellate to spindle-shaped fibroblasts, regularly disposed in a dense fibrillar collagen background. No deposition of either collagen or bone matrix was seen. Some small blood vessels were spread in the stroma. The above reported inflammatory foci showed typical features of chronic inflammation, with lymphoid cells but no granulocytes.The discrete mass here described can be defined as localized gingival hyperplasia or fibrous epulis for its features, i.e. mature fibrous tissue accompanied by chronic-active inflammatory reaction.