Denticles !

1. Denticles! Equine Odontogenic Tumors Accessions: 128549, 128572

2. Jewel • 3 yo Belgian Filly • Presents for undescribed abnormalities noted on routine dental exam, no dysphagia • PE: palpable asymmetry to the hemimandibles, mild right mandibular lymphomegaly • Orally, the occlusal surface of 410 is replaced by cobblestone-like surface of multiple "dental islands" with deep periodontal and intradental pocketing • Local feed impaction with fermented odor

4. Insert CT images

5. P.M. Dixon, I. Dacre / The Veterinary Journal 169 (2005) 165–187

6. 2 wks after surgery Pre-surgical Post-surgical

7. Symptoms of oral tumors • Dysphagia, wt. loss, oral bleeding, grossly abnormal tissue, facial asymmetry and respiratory distress (maxillary tumors may impinge on the nasal passages) • Primary oral tumors in horses: • Odontogenic • Pure epithelial, mixed epithelial and mesenchymal • Slow growing masses • Osteogenic • Soft tissue origin • FNA may not achieve representative samples to allow for an accurate diagnosis

8. Odontogenic tumors • Calcified tumors • ODONTOMA=Dentinal tissue • Combinations of all dental components=compound odontoma or ameloblasticodontoma • CEMENTOMA=Cementum • Usually slow growing, hard focal mandibular or maxillary masses, very radio-opaque • Usually do not have draining tracts and the swelling exceeds that of periapical abscessation • Px depends on border definition and surgical resectability • Non-calcified tumors • AMELOBLASTOMA • Derived from epithelium that forms enamel • Do not induce connective tissue formation • Freq expansile soft tissue mass with resorption of adjacent teeth and bone P.M. Dixon, I. Dacre / The Veterinary Journal 169 (2005) 165–187

9. Calcified masses Odontomas (including ameloblasticodontomas) and Cementomas

10. Odontomas=Dentinal tissues • Rare, benign, locally expansive tumors of dental origin • Odontomas are classified as hamartomas instead of neoplasms: normal tissues in a chaotic arrangement: enamel, dentin, cementum and occas pulp • Complete surgical excision is curative • Odontomas • epithelial and mesenchymal elements, induce connective tissue proliferation within the tumor (induction separates these from ameloblastomas) • Young, no known sex predilection, maxilla>mandible • Classification • Compound-reported, rarely, in horses, dogs, and cattle • have all the features of normal tooth formation • Well-organized tooth-like structures known as denticles are often found • Complex-more differentiated than ameloblastic, w/ dental tissues arranged in a disorganized structure • Ameloblastic-most undifferentiated form, not common in horses JAVMA, Vol 225, No. 9, November 1, 2004

11. Compound odontomas • PE: Young animals (<1 year), epulis-like growth or firm bony mass, no oral mucosal defect, non painful, no soft tissue swelling, may affect nasal airflow if maxillary • Rads: Well-marginated osseous-like mass encircling the alveolus, or centered around teeth. Tooth may be abnormally shaped and positioned, with indistinct alveolus. No evidence of lysis or fracture JAVMA, Vol 225, No. 9, November 1, 2004

12. Compound Odontoma • Histopathology • Multiple tooth-like structures and foci of normal bone; Denticles consist of a core of primitive mesenchyme resembling dental pulp, surrounded by a disorganized layer of odontogenic epithelium and a distinct zone of dentin, with an outer border that is disorganized and discontinuous of primitive ameloblasts • Aggressive surgical excision required for cure JAVMA, Vol 225, No. 9, November 1, 2004

13. Radiographic differentials: • Primary bone tumor • Osteoma • Ossifying fibroma • Primary dental tumor • Complex or compound odontoma • Ameloblasticodontoma • Ameloblastoma (usually not as mineralized) JAVMA, Vol 225, No. 9, November 1, 2004

14. JAVMA, Vol 225, No. 9, November 1, 2004

15. Complex Odontoma • Less differentiated than compound odontomas • Reported appearance in a case series: • Firm, smoothly rounded, raised mass • Mass centered over the crown, with a radio-opaque rim interspersed with lucent and mineralizing opaque areas (similar to that of enamel) • Normal dental sac structures present in all cheek teeth • Differential diagnoses • Periapical abscessation • Cyst • Ossifying fibroma • Malignant neoplasia-SCC and myomatous tumors • Odontogenic tumors v

16. Complex Odontoma • Reported radiographic appearance includes: • Multilobulated masses within a well-differentiated cyst-like structure • Differentiated from compound odontomas in that compound odontomas are organized into recognizable tooth structures • Locally aggressive, but complete surgical excision is curative

17. Complex Odontoma • At surgery, mass was cystic containing white, mineralized tissue suspended within • HxPx: Odontogenic epithelium and stellate reticulum. Material resembling cementum with nests of epithelial rests and chords of cells with early differentiation into ameloblastic cells with abnormal looking enamel matrix • Epithelial components: ameloblasts and stellate reticulum • Mesenchymal components: cementum and pulp

18. Cementomas=Cementum • Rare odontogenic neoplasm of mesenchymal origin (Not an odontoma since not epithelial component) • Excessive deposition of cementum-like tissues • Slow-growing tumor of cementoblasts, deposit differentiated cemental matrix around the root, proliferation of cementoblasts and destruction of the lamina dura • Well-circumscribed, rounded, radio-opaque masses surrounding the roots of several incisors or premolars; deformation of surrounding alveolar bone and effacement of lamina dura (effacement of lamina dura differentiates this from hypercementosis)

19. Cementoma

20. Cementomas • Histopathologically • Prominent, well-differentiated and demarcated proliferation of cementum-like material with collagen and abn lacunae surrounding normal dental structures, including dental pulp, dentin, and cementum • Etiology • Possibly hereditary in humans, or due to a reactive/hyperplastic response after periodontal trauma • May occur any age (2-17 yr range) • Differential: hypercementosis=non-neoplastic process • Excessive cementum accumulation in continuation with the normal radicularcementum, lamina dura is usu preserved • Usually not as disruptive

21. Non-calcified masses Ameloblastoma

22. Ameloblastoma • Ameloblastomas: major Ddx for odontomas • Characterized by a predominance of odontogenic epithelium • Large amts of odontogenic epithelial tissue, lack inductive differentiation of dentin and enamel • More common in the mandible of older horses, but can be seen in foals • Tend to be osteolytic and uni- or multilocular • Keratinizing ameloblastoma: lg amounts of epithelial keratin throughout the lesion • Ameloblastic carcinomas: more differentiation toward ameloblastic epithelium • Ameloblasticodontomas: radiolucent or partially mineralized with occas foci of enamel***

23. Histopathology on Jewel • Right mandible, teeth: The majority of the mass is composed of disorganized extracellular matrix associated with a dense band of inflamed fibrovascular connective tissue which contains a few small islands of epithelial cells consistent for rests of Malassez. Adjacent to this mass is a large tooth composed of degenerate, variably mineralized and disorganized, and possibly necrotic dentin. The mass is composed predominantly of matrix consistent for cementum, but is poorly organized into large aggregates with anastomosing, irregular cords. The matrix is pink with lacunae-trapped cells and multiple blue resting lines. In one section the matrix forms a plexiform arrangement with clear spaces in between creating a “swiss-cheese” like mass. • We shared slides with two pathologists and favor a diagnosis of cementoma. Cementoma is a benign lesion and does not metastasize. The lesion extends to the tissue margins.