Ameloblastic Fibro-Odontoma in a Bovine

Abstract

Background: Ameloblastic fibro-odontoma is a benign tumor derived from odontogenic epithelium and mesenchymal tissue, which forms enamel and dentin. It is a rare neoplasm in all species. One of the most common sites for their occurrence is the anterior mandibules. The prevalence of this odontogenic tumor is higher in young animals and only few cases are described in cattle. The purpose of this article is describe the clinical, surgical and the histopathological characteristic of a fibro-odontoma case in a Jersey Cow. Case: A 3-year-old Jersey cow was presented with a progressively growing mass in the anterior mandible displacing the incisor teeth. The mass measured approximately 12 cm diameter and there was a focal area of myiasis. The owner reported weight loss and eating difficulties. The animal was treated with antibiotics for a few weeks but the conservative treatment failed, and the heifer underwent surgical removal of the lesion. The tumor was sent for histopathological evaluation at UFPR-Palotina Pathology laboratory. Microscopically, the excised mass was poorly delimited, and was composed of tumor cells of mesenchymal and epithelial origin which infiltrated and compressed surrounding tissues. Neoplastic cells were arranged in bundles which multifocally formed dental sacs (dental follicles) of various sizes. These dental sacs were formed by neoplastic ameloblasts, and were surrounded by abundant fibrous connective tissue. The central zone of the tumor consisted of a loose, vacuolated neoplastic stellate reticulum. Mitotic figures were rare, and there was moderate anisokaryosis. In some areas, neoplastic ameloblasts surrounded the stellate reticulum. The presence of a sparse, well-organized basophilic extracellular matrix produced presumably by the tumor cells and interpreted as dentin. These microscopic characteristics led to the diagnosis of an ameloblastic fibro-odontoma. The heifer made a full recovery after surgical removal of the mandibular mass.Discussion: Although rare in all mammalian species, ameloblastic fibro-odontoma is the most common odontogenic tumor in cattle. There are also reports of this neoplasm in humans, cats, horses, sheep, nonhuman primates and rats. Despite being benign these neoplasms may be infiltrative or expansile which make them difficult to be surgically removed. Similar to observed in this case the most majority of these tumors occurs in the anterior mandibules of young cattle of either sex. The ameloblastic fibro-odontoma is a variant of ameloblastic fibroma in which mineralized tissue is absent.  Ameloblastic fibro-odontoma is a tumor formed by odontogenic epithelial and mesenchymal tissues which form enamel or dentin (or both). The presence of enamel helps the pathologist to diagnose an ameloblastic fibro-odontoma by histopathology in the slides. Surgical excision of the neoplasm with wide margins should be performed in order to reduce the risk of local recurrence of this tumor, and when well executed they are curative. In this animal there was no recurrence of the neoplasm after a 16-month follow-up. Ameloblastic fibro-odontoma, other odontogenic neoplasms, inflammatory lesions due to infectious agents such as bacteria and fungi, and congenital lesions should be considered in the differential diagnosis of young cattle presented with localized swelling of the maxillae or oral cavity.