Odontomes and Odontogenic Tumors

1. Odontomes and Odontogenic Tumors Dr. HamzahBabkair BDS Oral Pathology Demonstrator

2. Odontomes • Odontome (or odontoma): non-neoplastic, developmental anomaly or malformation that contains fully formed enamel and dentin. • They can be considered as dental hamartomas containing dental calcified tissues. • Classifications may vary, and some include odontomes with odontogenic tumors.

3. Invaginatedodontome (dens invaginatus, dens-in-dente) Evaginatedodontome Enamel pearl (enameloma) Geminated odontome Complex odontome Compound odontome These are better considered as structural anomalies of teeth rather than odontomes. Odontomes

4. Complex & Compound Odontomes • Complex odontome is a developmental tumor-like mass consisting of disorderly arranged dental tissues. • Compound odontome is a developmental tumor-like mass consisting of numerous small, discrete, tooth-like structures. • They have limited growth potential and can be considered as dental hamartomas. • Gradations between the 2 types exist. • Both are often diagnosed in 2nd decade of life.

5. Complex & Compound Odontomes • Complex odontome occurs mostly in premolar-molar regions, especially in mandible. • Compound odontome mostly occurs in the anterior maxilla. • Majority of odontomes are small and arise in association with permanent dentition. • Often discovered as incidental radiographic findings. • Occasionally, they cause expansion. • In some cases, this is associated with dentigerous cyst formation around the odontome.

6. Complex & Compound Odontomes • The majority of odontomes are associated with the crowns of unerupted teeth. • Occasionally, they take the place of a missing tooth. • Odontomes of long duration may appear to erupt following resorption of overlying bone, sometimes leading to secondary infection. • Multiple odontomes are rare.

7. Complex & Compound Odontomes: Histopathological Features Complex odontome: mass of irregularly arranged, well-formed enamel, dentin, pulp & cementum surrounded by a fibrous capsule. Compound odontome: a number of separate denticles embedded in fibrous tissue.

8. Complex & Compound Odontomes: Histopathological Features Both developing complex and compound odontomes contain varying amounts of odontogenic epithelium and structures resembling enamel organs. They show all stages of odontogenesis and may be difficult to differentiate from ameloblasticfibroma and ameloblastic fibro-odontoma.

9. Odontogenic Tumors • Odontogenic tumors are uncommon lesions, some of them are rare. • The nomenclature and classification used is based on those recommended by the WHO (1992) and its Consensus Conference (2003). • The latter redesignated the OKC as the keratinizing cystic odontogenic tumor, although in this textbook and others it is still referred to as a cyst. • Likewise, the calcifying odontogenic cyst has been redesignated as the calcifying cystic odontogenic tumor.

10. Classification of Odontogenic TumorsBenign Odontogenic Tumors Epithelial lesions: (1) Without odontogenicmesenchyme • Ameloblastoma • Squamousodontogenic tumor • Calcifying epithelial odontogenic tumor • Adenomatoidodontogenic tumor • Keratinizing cystic odontogenic tumor

11. Classification of Odontogenic TumorsBenign Odontogenic Tumors Epithelial lesions: (2) With odontogenicmesenchyme • Ameloblasticfibroma and fibrodentinoma • Ameloblastic fibro-odontoma • Odontoamaloblastoma • Calcifying odontogenic cyst and dentinogenic ghost cell tumor • Calcifying cystic odontogenic tumor (calcifying odontogenic cyst) and dentinogenic ghost cell tumor • Complex odontome* • Compound odontome*

12. Classification of Odontogenic TumorsBenign Odontogenic Tumors Mesenchymal lesions: • Odontogenicfibroma • Myxoma • Cementoblastoma

13. Classification of Odontogenic TumorsMalignant Odontogenic Tumors Odontogenic carcinomas: • Malignant ameloblastoma/ameloblastic carcinoma • Primary intra-osseous carcinoma • Clear cell odontogenic carcinoma • Malignant variants of other epithelial tumors • Malignant change in odontogenic cysts Odontogenic sarcomas: • Ameloblasticfibrosarcoma • Ameloblastic fibro-odontosarcoma

14. Classification of Odontogenic TumorsTumors of Debatable Origin • Melanoticneuroectodermal tumor of infancy • Congenital gingival granular cell tumor (congenital epulis)

15. Ameloblastoma • “Benign” locally invasive neoplasm derived from odontogenic epithelium. • Rare but commonest of odontogenic tumors (without odontomes considered). • ~1% of all oral tumors. • More common in black Americans and West Africans. • 2 more variants, unicystic and peripheral are worth separate discussion.

16. Ameloblastoma: Clinical Features • Wide age range. • 80% occur in the mandible. • The majority of mandibular lesions (~90%) occur in posterior areas and ramus. • The majority of maxillary lesions also occur in posterior areas, ~15% involve the antrum. • Slow growing & asymptomatic in early stages.

17. Ameloblastoma: Clinical Features As it gets larger, there may be gradual facial deformity and bone expansion. Enlargement is usually bony-hard, non-tender, and ovoid to fusiform. In advanced cases, egg-shell crackling may be felt due to thinning of cortex. Perforation of bone and extension into soft tissue are late findings. In the maxilla, even large tumors may cause little expansion since the lesion can expand into the sinus. Teeth may become loose, but pain is seldom a feature.

18. Ameloblastoma: Radiographic Features Most commonly appears as a multilocularradiolucency. Root resorption of involved teeth. May be associated with an unerupted tooth, particularly an impacted 3rd molar. The appearance then may mimic a dentigerous cyst. Less frequently, it may present as a unilocularradiolucency.

19. Ameloblastoma: Histopathological Features Variable patterns depending on arrangement of neoplastic epithelium. Follicular pattern: - Discrete, rounded islands or follicles, each resembling the enamel organ. - Stellate reticulum –like cells at center, surrounded by cuboidal or columnar cells resembling ameloblasts. - Nuclei of peripheral cells are polarized away from the basement membrane. - Islands are separated by varying amounts of fibrocollagenousstroma.

20. Ameloblastoma: Histopathological Features • Follicular pattern: Several changes can occur within the stellate area, including cystic breakdown, squamous metaplasia, and granular cell change. • Plexiform pattern: epithelium arranged as a tangled network of strands and irregular masses, each showing the same cell layers seen in the follicular pattern. • Cyst formation in this pattern occurs within the stroma rather than the epithelium.

21. Ameloblastoma: Pathogenesis • General opinion supports origin from dental lamina or its residues. • Other sources include the epithelial lining of odontogenic cysts and the basal layer of oral epithelium (peripheral ameloblastoma). • No enamel is formed in this tumor, and the columnar or cuboidalcellls at the periphery of epithelial islands are thought to represent pre-ameloblasts.

22. Ameloblastoma: Behavior Typical ameloblastoma is locally invasive and tumor islands infiltrate cancellous marrow spaces without initially causing bone destruction. This requires wide surgical excision with normal margins to avoid recurrence (50-90%). Rare reports of pulmonary metastasis of ameloblastoma are probably the result of aspiration of tumor cells associated with surgery. Truly malignant ameloblastomas are rare.

23. Unicystic Ameloblastoma Typically presents in a younger age group than other variants 2nd-3rd decade). Radiographically, it appears as a well-defined, unilocularradiolucency, usually associated with an unerupted tooth, i.e. similar to dentigerous cyst. The diagnosis is made only after histopathological examination. Treatment is conservative, since epithelium in most cases is limited to cyst lumen. If epithelium infiltrates the cyst wall, it should be treated like typical ameloblastoma.

24. Peripheral (Extraosseous) Ameloblastoma Rare variant which arises in gingival or alveolar soft tissues without involving bone. May arise from basal cell layer of oral epithelium, or from extraosseous dental lamina remnants. Much less invasive, and treatment is conservative.