Revision 62 for 'Ameloblastoma'

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Ameloblastoma

Ameloblastomas, previously known as an adamantinoma of the jaw, are benign, locally aggressive tumors that arise from the mandible, or less commonly from the maxilla. Usually presented as a hard painless lesion near the angle of the mandible in the 3rd to 5th decades of life. 

Epidemiology

Ameloblastomas are the second most common odontogenic tumor (odontoma is the most common) and account for up to one-third of such cases.

They are slow growing and tend to present in the 3rd to 5th decades of life, with no gender predilection 4.

Clinical presentation

Ameloblastomas typically occur as hard painless lesions near the angle of the mandible in the region of the 3rd molar tooth (48 and 38) although they can occur anywhere along the alveolus of the mandible (80%) and maxilla (20%). When the maxilla is involved, the tumor 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

Unsurprisingly, ameloblastomas 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 multilocualted (80%), expansile "soap-bubble" lesion, with well demarcated borders and no matrix calcification. Occasionally erosion of the adjacent tooth roots can be seen which is highly specific. When larger it may also erode through cortex into adjacent soft tissues.

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. These components tend to vividly enhance.

Treatment and prognosis

Ameoloblastomas tend to be treated by 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. The latter has an elevated risk of recurrence.

Malignant behavior is seen in two forms 5:

  1. ameloblastic carcinoma
    • frankly malignant histology
  2. malignant ameloblastoma
    • metastases despite well differentiated 'benign' histology

Differential diagnosis

General imaging differential considerations include:

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