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Ameloblastoma

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AMELOBLASTOMA: CLINICAL FEATURES, RADIOLOGY AND TREATMENT              

AUTHOR: Sanketh DS, MDS

INTRODUCTION

Ameloblastoma, is the most common, clinically significant odontogenic tumor. It was known to be the second most common odontogenic tumor after odontoma, but is now increasingly thought to be the most common especially in Asia and Africa. In fact recent studies show ameloblastoma to be the most common odontogenic tumor in India (Sriram and Shetty (2008), Deepthi et al (2016), Nalabolu et al(2016)). 

This tumor was called adamantinoma in the early 1900’s and the name was subsequently changed to ameloblastoma in 1930.

Ameloblastomas are slow growing locally invasive tumors and run a benign course. However, there are cases of ameloblastomas that have become malignant. Such tumors are then called malignant ameloblastoma or ameloblastic carcinoma, both being distinct malignant entities. Ameloblastoma has been segregated into 4 different types or presentations, due to differing therapeutic considerations and prognosis:

1. Conventional solid/multicystic ameloblastoma
2. Unicystic ameloblastoma
3. Desmoplastic ameloblastoma
4. Peripheral ameloblastoma

The discussion in this presentation would pertain to conventional ameloblastoma. It is generally agreed that ameloblastomas arise from the remnants of odontogenic epithelium, especially from the rests of the dental lamina or from a developing enamel organ.

If these remnants are situated in the soft tissue like the gingival mucosa, it could, along with the basal cells of the mucosal epithelium, give rise to peripheral variant of ameloblastoma. It is also believed to arise from the epithelial rests of Malassez.

It is known that ameloblastomas may occur due to changes in the lining of non-neoplastic cysts like dentigerous cysts and may originate in the walls these cysts.

CLINICAL FEATURES

Conventional ameloblastoma, though a benign lesion, has the biologic behaviour of a low grade malignant tumor.

It is slow growing, locally invasive and has high rates of recurrence after treatment. Ameloblastoma may be asymptomatic in the early stages but later gradually increases in size causing facial asymmetry, loosening of teeth and very rarely pain. The tumor may enlarge to the extent of thinning the bone and cause egg-shell crackling.

Age

Conventional solid/multicystic ameloblastomas occur across a wide age range, from the third to the seventh decades of life. Though most cases cluster between this age range, the average age of diagnosis is reported to be in the range 33-39 years. About 10% of the cases are reported to arise in children.

Gender

It has an almost equal gender predilection of 1.1:1 for male:female.

Location

About 80-85% of conventional ameloblastomas occur in the mandible the molar-angle-ramus area. In fact this area is involved three times more than the premolar and anterior areas of the mandible combined! The remaining occurs in the maxilla, usually in the posterior regions.

RADIOLOGY

Most typically ameloblastomas are multilocular in appearance – described as having either a soap-bubble appearance (when the loculations are large) or honeycombed appearance (when loculations are small).  

It may also appear with a unilocular picture associated with an unerupted tooth. Radiographs may reveal root resorption,bone resorption, tooth displacement, displacement of sinus and expansion of cortical plates.

TREATMENT

The treatment of ameloblastoma has been a subject of controversy for many years, ranging from a simple enucleation and curettage to an en bloc resection. Curettage is less desirable as it is associated with high recurrence of around 50-90%. However, en bloc resection has been known to reduce recurrence of the tumor (if curettage to 15%. Radiotherapy is not the treatment of choice since it could potentially trigger the tumor to become malignant.

DIFFERENTIAL DIAGNOSIS

The 2 general radiographic presentations for ameloblastoma are unilocular or multilocular pattern:

a) If unilocular, the differentials may be:
dentigerous cyst and keratocystic odontogenic tumor(KCOT).

Occasionally if there is a unilocular lesion in the anterior region, adenomatoid odontogenic tumor could be considered particularly if the individual is in his/her 2nd decade.

b) If multilocular, a range of differentials could be considered:
KCOT, giant cell granuloma, odontogenic myxoma, central hemangioma

REFERENCES

Rajendran R, Sivapathasundaram B. Shafer’s Textbook of Oral Pathology. 8 th ed. Elsevier; 2016.

Neville BW, Damm DD, Allen CM, Chi A. Oral and Maxillofacial Pathology. South Asian ed. Elsevier; 2016.

Wood NK, Goaz PW. Differential Diagnosis of Oral and Maxillofacial Lesions. 5 th ed. Mosby; 1997.

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