An ameloblastoma (previously known as an adamantinoma of the jaw) is a benign but locally agressive tumour arising from the mandible, or less commonly from the maxilla.
Ameloblastomas are the second most common odontogenic tumour (odontoma is the most common) and account for up to a 3rd of such cases.
They are slow growing and tend to present in the 3rd to 5th decades of life, with no gender predilection 4.
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 anywere 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 unerrupted teeth.
Ameloblastomas (not surprisingly) arise from ameloblasts, (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
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.
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 recurrance (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 behaviour is seen in two forms 5:
- frankly malignant histology
- metastases despite well differentiated 'benign' histology
- dentigerous cyst : the relationship between ameloblastomas and dentrigerous cysts is a controversial one: 20% of ameloblastomas thought to arise from pre-existing dentigerous cysts
- odontogenic keratocyst (OKC) : usually unilocular with thin poorly enhancing walls
- odontogenic myxoma : can be almost indistiguishable
- aneurysmal bone cyst (ABC)
- fibrous dysplasia
- 1. Dunfee BL, Sakai O, Pistey R et-al. Radiologic and pathologic characteristics of benign and malignant lesions of the mandible. Radiographics. 26 (6): 1751-68. doi:10.1148/rg.266055189 - Pubmed citation
- 2. Minami M, Kaneda T, Ozawa K et-al. Cystic lesions of the maxillomandibular region: MR imaging distinction of odontogenic keratocysts and ameloblastomas from other cysts. AJR Am J Roentgenol. 1996;166 (4): 943-9. AJR Am J Roentgenol (abstract) - Pubmed citation
- 3. Minami M, Kaneda T, Yamamoto H et-al. Ameloblastoma in the maxillomandibular region: MR imaging. Radiology. 1992;184 (2): 389-93. Radiology (abstract) - Pubmed citation
- 4. Dunn JL, Olan WJ, Bank WO et-al. Giant ameloblastoma: radiologic diagnosis and treatment. Radiographics. 17 (2): 531-6. Radiographics (citation) - Pubmed citation
- 5. Ciment LM, Ciment AJ. Malignant ameloblastoma metastatic to the lungs 29 years after primary resection: a case report. Chest. 2002;121 (4): 1359-61. doi:10.1378/chest.121.4.1359 - Pubmed citation
Synonyms & Alternative Spellings
|Synonyms or Alternative Spelling||Include in Listings?|
|Adamantinoma of the jaw||✓|
|Ameloblastoma of jaw||✗|
|Ameloblastoma of the jaw||✗|
|Adamantinoma of jaw||✗|