AMELOBLASTOMA

A.K.A: Adamantinoma of the jaw  ( Short Note 2003 )

Definition:

Benign, locally aggressive tumours that arise from the mandible, or less commonly from the maxilla.

 

Epidemiology:

Ameloblastomas are the second most common odontogenic tumour (odontoma is the most common)

3rd to 5th decades of life

No gender predilection

 

Clinical presentation:

Hard painless slow growing mass near the angle of the mandible in the in the region of the 3rd molar tooth (48 and 38)

Can occur anywhere along the alveolus of the mandible (80%) and maxilla (20%).

When the maxilla is involved, the tumour is located in the premolar region, and can extend up in the maxillary sinus.

Although benign, it is a locally aggressive neoplasm with a high rate of recurrence. Approximately 20% of cases are associated with dentigerous cysts and unerupted teeth.

 

Pathology:

Arise from  ameloblasts, which are part of the odontogenic epithelium, responsible for enamel production and eventual crown formation.

 

Three variants are described:

simple (no nodule): best prognosis

luminal: single nodule projecting into the cyst

mural: multiple nodules (often only microscopic) in the wall of the cyst

 

Radiographic features

Plain film and CT

It is classically seen as a multiloculated (80%), expansile “soap-bubble” lesion, with well demarcated borders and no matrix calcification.

MRI

In general ameloblastomas demonstrate a mixed solid and cystic pattern, with a thick irregular wall, often with papillary solid structures projecting into the lesion.

 

Treatment and prognosis

surgical en-bloc resection.

Local curettage is associated with a high rate of local recurrence (45-90%).

Simple unicystic lesions are less common but have a better prognosis. Simple (no nodule) variant will not be diagnosable on radiography, as it will be indistinguishable form other more common cysts. Luminal variant, has a single nodule projecting into the cyst.

Mural variant has multiple nodules (often only microscopic) in the wall of the cyst. has an elevated risk of recurrence.

 

 

Malignant behaviour is seen in two forms :

  1. ameloblastic carcinoma
  • frankly malignant histology
  1. malignant ameloblastoma
  • metastases despite well differentiated ‘benign’ histology

 

Differential diagnosis

  1. dentigerous cyst: the relationship between ameloblastomas and dentigerous cysts is a controversial one, 20% of ameloblastomas thought to arise from pre-existing dentigerous cysts
  2. odontogenic keratocyst (OKC): usually unilocular with thin poorly enhancing walls
  3. odontogenic myxoma: can be almost indistiguishable
  4. aneurysmal bone cyst (ABC)
  5. fibrous dysplasia

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