Gingival neoplasm presenting as an ossifying epulis in a parrot cichlid fish (Hoplarchus psittacus)

This report describes the histopathological features of an ossifying epulis, measuring 1.5 × 1 × 1 cm in length, width and height, respectively, on the lingual surface of the lower jaw of a 2.5 year-old parrot cichlid (Hoplarchus psittacus) from a commercial aquarium. The tumor had appeared in the oral cavity three months prior to its introduction to the laboratory for diagnosis. Grossly, the neoplastic mass was pale-tan with a shiny, smooth surface and coalescing areas of hemorrhage. Microscopically, the overlying epithelium was hyperplastic and extended deeply into the underlying stroma. The stroma consisted of well vascularized collagenous tissue and neoplastic fibroblasts associated with irregular cords and islands of mineral deposition as dentin-like materials confirmed by Masson's trichrome and Goldner's trichrome staining.