Ameloblastoma

AMELOBLASTOMA - a benign odontogenic tumor

1. AMELOBLASTOMA Dr.Faisal K A Tutor Malabar Dental College and Research Centre

2. CONTENTS Introduction Pathogenesis Clinical classification Clinical features Radiographic features Histological features Management P rognosis Conclusion

3. INTRODUCTION (adamantinoma , adamantoblastoma ) Ameloblastoma is a true neoplasm of enamel organ type tissue which does not undergo differentiation to a point of enamel formation Definition ‘’Being a tumor that is usually unicentric , non functional ,intermittent in growth , anatomically benign and clinically persistent’’ Robinson

4. The term ameloblastoma as applied to the particular tumor was suggested by Churchill in 1934 It is the second most common odontogenic neoplasm

5. PATHOGENESIS Tumor conceivably may be derived from, Cell rests of the enamel organ, either remnants of the dental lamina or Hertiwig’s sheath, epithelial rests of malassez Epithelium of odontogenic cysts Disturbances of the enamel organ Basal cells of the surface epithelium of the jaw Heterotropic epithelium in other parts of the body ,especially pituitary gland

6. C linical classification U nicystic ameloblastoma C onventional or multicystic or solid ameloblastoma P eripheral (extraosseous)ameloblastoma M alignant ameloblastoma P ituitary ameloblastoma(craniopharyngioma, or Rathke’s pouch tumour)

7. Conventional solid or multicystic intraosseous ameloblastoma Clinical features It is rare in children younger than age 10 Prevalence in the third to seventh decade of life No sex predilection 80% to 85% of the cases occur in mandible ,most often in molar ascending ramus area Often asymptomatic and smaller lesions are detected only during a radiographic examination

8. A painless swelling or expansion of the jaw is the usual clinical presentation If untreated ,then the lesions may grow slowly to massive or gortesque proportions Pain and parasthesia are uncommon

9. Radiographic features Multilocular radiolucent lesion Soap bubble appearance or as being honey combed Buccal and lingual cortical expansion is frequently present resorption of the root of the adjacent tooth Margins of the radiolucent lesion show irregular scalloping

10. Histopathologic features Conventional solid ameloblastoma show remarkable tendency to undergo cystic change ,grossly most tumors have varying combination of cystic and solid features This includes Follicular Plexiform pattern Acanthomatous Granular cell Desmoplastic Basal cell type

11. Follicular pattern Most common and recognizable Islands of epithelium resemble enamel organ epithelium in a mature fibrous connective tissue stroma The epithelium nests consists of a core of loosely arranged angular cells resembling the stellate reticulum of an enamel organ A single layer of tall columnar ameloblast like cells surrounds this central core The nuclei of these cells are located at the opposite pole to the basement membrane

12. The peripheral cells may be more cuboidal and resemble basal cells Cyst formation is common and vary from micro cyst ,which form within the epithelial islands to large macroscopic cysts

13. Plexiform pattern Consists of long anastomosing cords of larger sheets of odontogenic epithelium The cords or sheets of epithelium are bounded by columnar or cuboidal ameloblast like cells surrounding more loosely arranged epithelial cells Supporting stroma tends to be loosely arranged and vascular Cyst formation is usually uncommon More often associated with stromal degeneration rather than cystic changes

14. Acanthomatous pattern When extensive squamous metaplasia ,often associated with keratin formation, occurs in central part of the epithelial islands of a follicular ameloblastoma ,the term acanthomatous ameloblastoma is sometime applied

15. Granular cell pattern it may show transformation of groups of lesional epithelial cells to granular cells These cells have abundant cytoplasm filled with eosinophilic granules that resemble lysosomes ultra structurally and histochemically This variant is seen in young patient M ore aggressive type H igh chance of recurrence rate ans metastasis

16. Desmoplastic pattern This type contains small islands and cords of odontogenic epithelium in a densely collagenized stroma Immunohistochemical studies have shown increased production of the cytokine known as transforming growth factor beta Peripheral columnar ameloblast like cells are inconspicuous about the epithelial islands

17. Basal cell pattern Least common Composed of nests of uniform basaloid cells, and they histopathologically similar to basal cell carcinoma of the skin No stellatereticulam present in the central portion of the nests Peripheral cells are cuboidal

18. Unicystic ameloblastoma Clinical features Seen most often in younger patients, second decade of Life 90% cases are found in the mandible, usually in the posterior region Asymptomatic , large lesions may cause a painless swelling of the jaw

19. Radiographic features Lesions typically appears as a circumscribed radiolucency that surround the crown of an unerupted mandibular third molar In some instances , the radiolucent area may have scalloped margins

20. Histopathological features Three variants Luminal unicystic ameloblastoma Intraluminal unicystic ameloblastoma Mural unicystic ameloblastoma

21. Luminal unicystic ameloblastoma The tumor is confined to luminal surface of the cyst Lesion consists of fibrous cyst wall with lining composed totally or partially of ameloblastic epithelium The lining demonstrate a basal layer of columnar or cuboidal cells with hyper chromatic nuclei with revers polarity and cytoplasmic vacuolization The upper epithelial cells are loosely cohesive and resemble stellate reticulum

22. Luminal Intraluminal

23. Intra luminal One or more nodules of ameloblastoma project from the cystic lining into the lumen of the cyst These nodule may small or largely fill the cystic lumen In some cases the nodule of tumor that project in to the lumen demonstrate an edematous ,plexiform pattern seen in the conventional ameloblastoma

24. Mural unicystic ameloblastoma The fibrous wall of the cyst is infiltrated by typical follicular or plexiform ameloblastoma

25. Treatment and prognosis Enucleation and curettage Recurrence rate 10 -20%

26. Peripheral ameloblastoma Uncommon Arises from rests of dental lamina beneath the oral mucosa Clinical feature Painless ,non nucleated ,sessile or pedunculated gingival or alveolar mucosal lesion Most examples are smaller than 1.5cm

27. Most often seen in middle aged patients Commonly found on the posterior gingival and alveolar mucosa More common in mandible Superficial alveolar bone become slightly eroded

28. Histopathologic features Islands of ameloblastic epithelium that occupy the lamina propria underneath the surface epithelium The proliferating ameloblastoma show any of the features described for the conventional ameloblastoma Treatment and prognosis Local surgical excision

29. Malignant ameloblastoma Clinical features Age range from 6 to 61 years No sex predilection Metastasis from ameloblastoma are found most in the lungs(aspiration or implant metastases ) Second-cervical lymph nodes Spread to vertebrae, bones and viscera has also occasionally been confirmed

30. Radiographic finding Same as nonmetastasizing ameloblastoma More aggressive lesion with ill defined margins and cortical destruction Histopathologic features Microscopic feature of ameloblastoma in addition to cytologic features of malignancy. Increased nuclear –cytoplasmic ratio Nuclear hyperchromatism Presence of mitoses Necrosis in tumor islands and dystrophic calcification

31. Treatment and prognosis Poor prognosis Aggressive resection

32. P ituitary ameloblastoma(craniopharyngioma, or Rathke’s pouch tumour) N eoplasm of the CNS that grows in a psedoencapsulated mass in the suprasellar or intrasellar area after destroying the pituitary gland M ost common tumour of childhood and adolescents with an average age of 3-23 years(25% of all CNS tumours) D erived from craniopharyngeal duct formed by Rathke’s pouch(oral ectoderm)

33. H istologically similar to oral ameloblastoma but also contains irregular calcified masses as well as occasional foci of metaplastic bone or g

34. management Treatment and prognosis En bloc resection or marginal resection Segmental Resection En bloc resection or marginal Resection

35. Segmental Resection If cortical bone is resorbed and penetrated , the resection should include periosteal layer A thin inferior border of the mandible in the first procedure may fracture ,if a reconstruction plate is not used to span and support the segment . If the complete excision of the tumor is ascertained by clinical and radiographic examination of specimen or intraoperative frozen section ,then immediate reconstruction can be undertaken

36. If there is uncertainty about resection margins ,reconstruction should be delayed until no recurrence is seen ,at least after six months postoperatively Adequate soft tissue coverage should be available ,if immediate reconstruction is planned It can be done by using an autogenous free bone grafts Or bank allogenic bone crib and autogenous bone marrow with a reconstruction plate Reconstruction plate with/without condylar prosthesis can be used in very old patients If sufficient soft tissue is not available ,a vascularized composite pedicle graft of bone and myocutaneous tissue can be used

37. In maxilla –aggressive resection is carried out Jackson and Callon Forte have given guide lines depending upon anatomical extents Tumor confined to maxilla without orbital floor involvement-partial maxillactomy Tumor involving the orbital floor ,but not the periorbital area-total maxillectomy Involving orbital contents-total maxillectomy with orbital extenteration Involving the skull-along with skull base resection –neurosurgical procedure

38. PERIPHERAL OSTEOTOMY Complete excision of tumour with a span of bone is retained-preserves the continuity of the jaw I nvolves careful exposure and curettage of all the visible tumour. T oremove mergins rotary instruments are used A dvantage: preservation of vital structures and bone integrity D isadvantage: seeding of the tumour into surrounding tissues

39. C autery D esiccation or electrocoagulation of the lesion, including various amounts of surrounding normal tissue . N ot commonly used, 50% recurrence rate S econdary ischemia and necrosis may occur

40. Conclusion Ameloblastoma is the most common clinically significant odontogenic tumor having three different clinicoradiographic presentation

41. R eferences TEXT BOOK OF ORAL AND MAXILLOFACIAL SURGERY- CHAPTER 44- NEELIMA ANIL MALIK TEXT BOOK OF ORAL AND MAXILLOFACIAL SURGERY- S M BALAJI

42. Thank you