Updating on ameloblastoma

This article gives a spot on one of the most controversial neoplasms of the face, which is Ameloblastoma and discusses its histopathological classification, clinical subtypes and ways of treatment

1. Dr.Mohammed El Sayed El Zayady OMF consultant BDS, Egyptian fellowship of oral & maxillofacial surgery Updating on AMELOBLASTOMA

2. Introduction: The ameloblastoma is one of the most controversial neoplasms of facial skeleton. Broca in 1868 gave the fist scientific description. Falkson in 1897 gave the term Adamantinoma . Churchill in 1929 introduced the current term Ameloblastoma.1,2 Non of the given terms is properly descriptive of the tumor ; Adam- antinoma : there is no enamel formed in the tumor and is not hard as the term implies. Ameloblastoma : suggesting origin from ameloblasts , however the ameloblasts are not the basic cells in all tumors.3

3. Definition: - A benign, locally aggressive tumor of odontogenic (tooth forming tissues) Epithelium.4 -Non encapsulated tumor .

4. Incidence: - 1% of all tumors of maxilla & mandible. -11% of all odontogenic tumors. -85% in mandible, almost in molar ramus region (70% in molar region, 20% in premolar area & 10% in incisor region). -15% in maxilla, almost in maxillary tubersity.5

5. Tissue of origin: Epithelium arising from enamel organ, follicle, periodontal ligament, lining of Dentigerous cyst, surface epithelium (peripheral) or marrow of jaws.

6. Pathological findings: Multilocular Ameloblastoma : according to histopathological findings , it is divided into:3 Follicular : Many small discrete islands, the cells are tall columnar with polarization of nuclei away from basement membrane, central portion of epithelial islands is composed of a loose network of cells resembling stellate reticulum. -Cystic formation is common in that pattern Plexiform : ameloblastic like cells are arranged in irregular masses and interdigitating cords bounded by columnar cells ,minimum stroma of stellate reticulum –like cells are found . Basal cell: Epithelial cells show very little tendency to differentiate and remain more or less basal in character, they are arranged in cords or sheets similar to basal cell carcinoma of the skin, in a loose fibrous stroma . Acanthomatous : Epidermoid features like epithelial pearls and prickle cells are marked, the cells occupying the position of stellate reticulum undergo squamous metaplasia sometimes with keratin formation in the central portion of the tumor islands . Granular cell: The epithelial cells are large, cuboidal or columnar with very coarse granular appearance, the acidophilic granules occur sometimes in the stellate reticulum like cells rather than the ameloblast – like cells (This type is said to be of particular clinical significance because of the increased risk of metastases ). Vascular: When many blood spaces are found replacing the stroma . Melanotic : Typical ameloblastic cells together with pigmented epithelial cells .

7. No correlation has been found between histological subtypes and its clinical behavior or treatment 6

8. Ameloblastoma invades the intertrabecular spaces of cancellous bone without accompanying resorption of trabeculae , it does not invade cortical bone, although it may erode it.3

9. (2) Unicystic Ameloblastoma : Was first described by Robinson and Martinez in 1977. 7 Features considered to justify the diagnosis of ameloblastoma in a cyst of the jaw.3 :- Hyperchromatism of basal cell nuclei of the epithelium lining the cystic cavity. Pallisading of basal cells and polarization of nuclei of basal cells lining the cystic cavity. Cytoplasmic vaculation of the basal cells.

10. According to WHO there are three distinct histological variants of the unicystic ameloblastoma and these features include:1,2 A relatively innocuous lining which may give way in parts to cell changes specific for ameloblastoma A nodule will project into lumen of a cyst and on examination, the nodule exhibits a plexiform pattern. Mural type: where part of the wall of cyst is infiltrated with typical plexiform or follicular ameloblastoma . (more aggressive)

11. Clinical features: No sex or racial predilection. Wide age range (20-50 years) but cases have been reported in children as well as old individuals. Slow growing painless swelling. Locally aggressive. High recurrence rate 5-15% following radical resection: the recurrence depending on (1) method of treatment of primary lesion, (2) extent of lesion, and (3) site of origin, recurrences may present after ten years or more.8 Large facial deformities. Malocclusion. Loosening of teeth. Ill-fitting dentures & bridges. Ulceration & periodontal disease.

12. 4 clinical subtypes ;   unicystic ameloblastoma : - Cystic lesion arises from lining of dentigerous cyst. - Less aggressive - Less common -Well circumscribed radiolucency . multicystic : - More common -Can grow to a large size -Can infiltrate into adjacent structures -Has a poorer prognosis than cystic lesion -Has a higher rate of recurrence - Radiographically appears as multilocular “soap bubble ” peripheral:9 - It is thought to arise from the surface epithelium or the remnants of the dental lamina. -Soft tissue extraosseous lesion -Occurs in alveolar mucosa -Underlying bone can be involved due to secondary erosion -Rare malignant : -The ameloblastomas with malignant tendencies have been known by variety of terms including:10 - Ameloblastic carcinoma -Malignant ameloblastoma

13. Ameloblastic carcinoma Malignant ameloblastoma -Rare   -Describes a tumor , regardless of biologic behavior with cytologic features of frank malignancy such as nuclear hyperchromatism , increased nuclear cytoplasmic ratio , prominent nucleoli, presence of mitosis and necrosis   -Diagnosis based on histologic criteria at initial biopsy -Rare   -Histologically benign appearing ameloblastoma primary in the jaw that produces similar benign appearing distant metastases.       -Only recognized when metastasis is documented. -Distant metastases especially to the lungs have been described but were attributed to aspiration and transportation rather than being blood borne.

14. Radiological Findings: The radiology of this lesion should include: Plain radiography Panoramic x-ray CT used to delineate soft tissue masses destruction of cortical bone and extension of tumor into adjacent structures. MRI used to provide information regarding edge definition and tumor consistency. Findings may include expansion of cortical plate with scalloped margins, multiloculations or “soap bubble” appearance and/or root resorption.8

15. Biopsy: Incisional biopsy is the most definitive way of differentiation between dentigerous cyst and ameloblastoma .

16. Treatment:   Depended on: -Clinical type -Location -Size of lesion -Age of patient

17. conservative surgery: Include * Curettage & enucleation Should not be used in the treatment of ameloblastoma because of high risk of recurrence. Recurrence rate is 55-90% for all ameloblastomas treated by enucleation & curettage. It is only appropriate in highly selected lesions affecting elderly individuals with other medical problems when it is desired to spare them a more extensive surgical procedures.

18. Radical surgery : 1-Marginal resection - Ameloblastoma is removed with a margin of normal bone at least 1cm. beyond the tumor margin. It is the treatment of choice in small solid or multicystic lesions . -Soft tissue borders at the time of resection may also be confirmed by frozen sections to ensure complete tumor removal . 2 -Segmental resection -Indicated with large tumors that have eroded the cortical bone and involved periosteum and soft Tissue. -When the cortex is thinned out without apparent perforation subperiosteal segmental resection may be attempted in order to spare the periosteum which will facilitate bone grafting. -Segmental resection also has to be considered in case of recurrent lesions .

19. *Incidence of recurrence following radical resection is 5-15%. * Ameloblastoma in posterior part of maxilla should be treated more extensively than similar lesion in the mandible, because of proximity to vital structures & difficulty in treating any recurrences. *Surgery may be followed by IMF.

20. Unicystic ameloblastoma is a pathological diagnosis in a lesion previously, on clinical basis was diagnosed and treated as a cyst, if enucleation was the treatment, no further surgical intervention is needed but the patient should receive periodic clinical and radiographical follow-up. If marsupialization was the treatment, another surgical approach is necessary in order to excise adequately the remaining part of lesion with a good safety margin. The first two variants of unicystic ameloblastoma are expected to be cured by enucleation , because the fibrous connective tissue wall of the cyst completely surrounds the tumor and provides an adequate margin of uninvolved tissues. Mural type needs more extensive surgical approach in order to avoid recurrence, this is because of the great possibility of involvement of the surrounding cancellous bone by tumor tissues from adjacent connective tissue wall.

21. Fellow up: Should be done for at least 5 years following surgery.

22. Discussion: Classification of ameloblastoma into solid, unicystic , peripheral and malignant forms is clinically sensible and important as it relates directly to the treatment plan.5 The various histopathological subtypes of the solid tumor are interesting but have no relevance to the ultimate treatment of the lesion.6 The management of malignant ameloblastoma should follow the same principles of other head and neck malignancies, including wide resection and consideration for metastatic disease.5 A good safety margin in cancellous bone is a must during excision of solid ameloblastoma which should pass the clinically and radiographically involved region, thus minimizing the chances of recurrence. Long – term follow up is mandatory. Radiotherapy has no place in the treatment of ameloblastoma because the tumor is radioresistant , also there is the danger of development of postradiation sarcoma or osteoradionecrosis.3

23. References   Reichart PA, Philipsen HP, Sonner S. Ameloblastoma . Biological profile of 3677 cases, oral oncology. European J. Cancer 31B, 1995:86-94. Kramer IRH, Pinborg JJ. Histologiocal typing of odontogenic tumors. 2 nd ed. Geneva: World Health Organization, 1995:11-4. Magid Amin,. Oral tumors. Oral& Maxillofacial surgery. 1 st ed. 1990: 181-184. Marquette University School of Dentistry, Ameloblastoma . Oral & Maxiollofacial Pathology. 2001. P.J.Dhanraani , Sami Al Abdulkarim . Ameloblastoma (Updated). Dental News. Volume IX. Number III. 2002. Slootweg PJ, Muller H. Malignant ameloblastoma or ameloblastic carcinoma. J Oral Surg 1984; 57:168. Robinson L, Martinez MG. Unicystic ameloblastoma : A prognostically distinct entity. Cancer 1977; 30:2278. Yan Trokel ,; Robert Himmelfarb ,; William Schneider; Robert Hou . An Update on the Management of a Recurrent Ameloblastoma : A Case Report and Review of Literature. Bucher A, Sciubba AA. Peripheral epithelial odontogenic tumors: A review. Oral Surg Oral Med Oral Pathol . 1987: 63-688. R.A. Cawson , E.W. Odell. Cawson’s Essentials of Oral Pathology and Oral Medicine. Odontogenic tumors and tumor-like lesions of the jaws. 7 th ed. 2002: 121-124 .