Ameloblastic Fibro-Odontoma in a Bovine

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.

Calcifying Cystic Odontogenic Tumor Associated with a Complex Odontoma

We present a case of a 16-year-old lad with a one year history of gingival mass of the left maxillary alveolar ridge. Excision revealed a cystic mass with brown fluid and irregular calcified material within the cavity. Histopathologic examination of the cyst lining shows a stratified cuboidal epithelium with palisading of the basal layer. The cells of the latter show reverse nuclear polarization reminiscent of ameloblastic epithelium. The superficial layers have a stellate reticulum-like appearance and contain large eosinophilic polygonal ghost cells. (Figure 1, 2) Some of the ghost cells show calcifications. (Figure 3) Sections from the hard, bony fragments show haphazard deposition of dentin and enamel-like material. (Figure 4) With these features, this case was called a calcifying cystic odontogenic tumour in association with a complex odontoma. Calcifying cystic odontogenic tumor (CCOT) is a benign neoplasm characterized by an ameloblastoma-like epithelium with ghost cells that often show calcification.1 It comprises only 2% of all benign odontogenic neoplasms.2 There is equal distribution of involvement for the maxilla and mandible, no sex predilection, with most cases diagnosed at the 2nd to 3rd decade of life.1,2 The classic histologic findings are the presence of a stratified epithelium consisting of cuboidal to columnar cells with reverse polarization of the basal layer and the presence of ghost cells. A stellate reticulum-like appearance of epithelial cells is also seen. Ghost cells are the most characteristic feature of CCOT and this may represent an abnormal type of keratinization or the coagulative necrosis of the odontogenic epithelium. 3 CCOT may present alone or in association with other odontogenic tumours.2, 4 Association with an odontoma has been reported in 20% to 24% of cases of CCOT.5 Complex odontoma is a hamartomatous lesion characterized by haphazard arrangement of matrix-producing epithelium, enamel, dentin and cementum-like tissue, in contrast to the more regular structure of a compound odontoma.1 CCOT associated with odontoma (CCOTaO), in contrast to CCOT alone, has a slight female predominance (2:1), a younger age of presentation (mean 16 years) and a predilection to the maxilla (61.5 %).5 Sidana et al. postulated several possible pathogenesis of CCOTaO including the possibility that CCOT develops secondarily from the epithelium involved in the formation of odontoma or that the odontoma develops secondarily from the epithelium in CCOT.5 Enucleation is the treatment of choice and is curative. A close histologic differential diagnosis is an acanthomatous ameloblastoma. Acanthomatous ameloblastoma contains distinct squamous epithelium within nests of ameloblastic epithelium, and ghost cells are absent. Very rarely, transformation into its malignant counterpart, ghost cell odontogenic carcinoma (GCOC), has been reported in recurrent cases.6, 7 Infiltrative borders, nuclear atypia and increased mitotic activity indicate this change.6, 7

Ameloblastic Fibrodentinoma Presenting as a False Gingival Enlargement in the Maxillary Anterior Region

Ameloblastic fibrodentinoma is a rare benign mixed odontogenic neoplasm usually occurring in the first two decades of life. It is more common in males and the most common site of occurrence is in the mandibular premolar molar area. This report presents a case of ameloblastic fibrodentinoma in a 12-year-old boy in the maxillary anterior region, a less common site for the occurrence of ameloblastic fibrodentinoma. A 12-year-old boy presented with a midline diastema in 11 and 21 region and a swelling in the palatal aspect of 11 and 12. Intraoral periapical radiograph showed the presence of rarefaction of bone on the mesial aspect of the cervical and middle third of the root of 11. Excision biopsy was done. The specimen was processed and stained with hematoxylin and eosin. Microscopic examination showed islands, chords and strands of odontogenic epithelium in a primitive ectomesenchyme resembling dental papilla. The odontogenic epithelium exhibited peripheral ameloblast-like and central stellate reticulum-like cells. The presence of dentinoid material was seen adjacent to the odontogenic epithelium in some foci. The lesion was diagnosed as ameloblastic fibrodentinoma.

Perlecan, a Basement Membrane-type Heparan Sulfate Proteoglycan, in the Enamel Organ: Its Intraepithelial Localization in the Stellate Reticulum

The localization and biosynthesis of perlecan, a basement membrane-type heparan sulfate proteoglycan, were studied in developing tooth germs by using murine molars in neonatal and postnatal stages and primary cultured cells of the enamel organ and dental papilla to demonstrate the role of perlecan in normal odontogenesis. Perlecan was immunolocalized mainly in the intercellular spaces of the enamel organ as well as in the dental papilla/pulp or in the dental follicle. By in situ hybridization, mRNA signals for perlecan core protein were intensely demonstrated in the cytoplasm of stellate reticulum cells and in dental papilla/pulp cells, including odontoblasts and fibroblastic cells in the dental follicle. Furthermore, the in vitro biosyntheses of perlecan core protein by the enamel organ and dental papilla/pulp cells were confirmed by immunofluorescence, immunoprecipitation, and reverse transcriptase-polymerase chain reaction. The results indicate that perlecan is synthesized by the dental epithelial cells and is accumulated in their intercellular spaces to form the characteristic stellate reticulum, whose function is still unknown.