Ameloblastoma

Changed by Amir Rezaee, 21 Oct 2016

Updates to Article Attributes

Body was changed:

Ameloblastomas are benign,are locally aggressive benign tumours that arise from the mandible, or less commonly from the maxilla. Usually presented as aslowly but continuously growing hard painless lesion near the angle of the mandible in the 3rd to 5th decades of life which can be severely disfiguring if left untreated

On imaging, they are commonly identified as a well-defined, expansive, and multiloculated ("soap bubble") lesion in the posterior mandible

Terminology

AmeloblastomasThe most common form of ameloblastomas - multicystic form - were previously known as adamantinomas of the jaw, although. Although both conditions are unrelated histologically and the latter terminology should be avoided. 

Epidemiology

Ameloblastomas are the second most common odontogenic tumour (odontoma is the most common overall but ameloblastoma is the most common lucent lesion) 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 tumour is located in the premolar region, and can extend up into 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  There are four forms has been 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
literature: unicystic, solid (multicystic), desmoplastic, and peripheral (extraosseous).
Histology

There are no specific histological features to differentiate between ameloblastomas and craniopharyngiomas, with only location differentiating between two tumours 6.

Radiographic features

Panoramic radiograph and CT

It isMulticystic ameloblastomas account for 80-90% of cases which are classically seen as a multiloculated (80%), expansile "soap-bubble" lesionlesions, 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 solid papillary structures projecting into the lesion. These components tend to enhance vividly which is very helpful to distinguish them from other lucent lesions of the mandible.

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 unilocular lesions are less common but have a better prognosis. Simpleand can be treated only by curettage:

  • simple (no nodule) variant will not be diagnosable on radiography, as it will be indistinguishable from other more common cysts. Luminal
  • luminal variant, has a single nodule projecting into the cyst. Mural
  • 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:

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

Differential diagnosis

General imaging differential considerations include:

  • -<p><strong>Ameloblastomas</strong> are benign, locally aggressive tumours that arise from the <a href="/articles/mandible">mandible</a>, or less commonly from the <a href="/articles/maxilla">maxilla</a>. Usually presented as a hard painless lesion near the angle of the mandible in the 3<sup>rd</sup> to 5<sup>th </sup>decades of life. </p><p>On imaging, they are commonly identified as a well-defined, expansive, and multiloculated ("soap bubble") lesion in the posterior mandible</p><h4>Terminology</h4><p>Ameloblastomas were previously known as <strong>adamantinomas of the jaw</strong>, although both conditions are unrelated histologically and the latter terminology should be avoided. </p><h4>Epidemiology</h4><p>Ameloblastomas are the second most common odontogenic tumour (<a href="/articles/odontoma">odontoma</a> is the most common) and account for up to one-third of such cases.</p><p>They are slow growing and tend to present in the 3<sup>rd</sup> to 5<sup>th </sup>decades of life, with no gender predilection <sup>4</sup>.</p><h4>Clinical presentation</h4><p>Ameloblastomas typically occur as hard painless lesions near the angle of the mandible in the region of the 3<sup>rd</sup> 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 tumour is located in the premolar region, and can extend up into the maxillary sinus.</p><p>Although benign, it is a locally aggressive neoplasm with a high rate of recurrence. Approximately 20% of cases are associated with <a href="/articles/dentigerous-cyst">dentigerous cysts</a> and unerupted teeth.</p><h4>Pathology</h4><p>Unsurprisingly, ameloblastomas arise from ameloblasts, which are part of the odontogenic epithelium, responsible for enamel production and eventual crown formation.</p><p>Three variants are described:</p><ul>
  • +<p><strong>Ameloblastomas </strong>are locally aggressive benign tumours that arise from the <a href="/articles/mandible">mandible</a>, or less commonly from the <a href="/articles/maxilla">maxilla</a>. Usually presented slowly but continuously growing hard painless lesion near the angle of the mandible in the 3<sup>rd</sup> to 5<sup>th </sup>decades of life which can be severely disfiguring if left untreated. </p><h4>Terminology</h4><p>The most common form of ameloblastomas - multicystic form - were previously known as <strong>adamantinomas of the jaw</strong>. Although both conditions are unrelated histologically and the latter terminology should be avoided. </p><h4>Epidemiology</h4><p>Ameloblastomas are the second most common odontogenic tumour (<a href="/articles/odontoma">odontoma</a> is the most common overall but ameloblastoma is the most common lucent lesion) and account for up to one-third of such cases.</p><p>They are slow growing and tend to present in the 3<sup>rd</sup> to 5<sup>th </sup>decades of life, with no gender predilection <sup>4</sup>.</p><h4>Clinical presentation</h4><p>Ameloblastomas typically occur as hard painless lesions near the angle of the mandible in the region of the 3<sup>rd</sup> 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 tumour is located in the premolar region and can extend up into the maxillary sinus.</p><p>Although benign, it is a locally aggressive neoplasm with a high rate of recurrence. Approximately 20% of cases are associated with <a href="/articles/dentigerous-cyst">dentigerous cysts</a> and unerupted teeth.</p><h4>Pathology</h4><p>Unsurprisingly, ameloblastomas arise from ameloblasts, which are part of the odontogenic epithelium, responsible for enamel production and eventual crown formation.  There are four forms has been described in the literature: unicystic, solid (multicystic), desmoplastic, and peripheral (extraosseous).</p><p> </p><h5>Histology</h5><p>There are no specific histological features to differentiate between ameloblastomas and <a href="/articles/craniopharyngioma">craniopharyngiomas</a>, with only location differentiating between two tumours <sup>6</sup>.</p><h4>Radiographic features</h4><h5>Panoramic radiograph and CT</h5><p>Multicystic ameloblastomas account for 80-90% of cases which are classically expansile "soap-bubble" lesions, with well-demarcated borders and no matrix calcification. Occasionally erosion of the adjacent tooth roots can be seen. When larger it may also erode through cortex into adjacent soft tissues.</p><h5>MRI</h5><p>In general, ameloblastomas demonstrate a mixed solid and cystic pattern, with a thick irregular wall, often with solid papillary structures projecting into the lesion. These components tend to enhance vividly which is very helpful to distinguish them from other lucent lesions of the mandible.</p><h4>Treatment and prognosis</h4><p>Ameoloblastomas tend to be treated by surgical en-bloc resection. Local curettage is associated with a high rate of local recurrence (45-90%).</p><p>Simple unilocular lesions are less common but have a better prognosis <span style="line-height:20.8px">and can be treated only by curettage</span><span style="line-height:1.6">: </span></p><ul>
  • +<li><span style="line-height:1.6">simple (no nodule) variant will not be diagnosable on radiography, as it will be indistinguishable from other more common cysts</span></li>
  • -<strong>simple </strong>(no nodule): best prognosis</li>
  • -<li>
  • -<strong>luminal:</strong> single nodule projecting into the cyst</li>
  • -<li>
  • -<strong>mural:</strong> multiple nodules (often only microscopic) in the wall of the cyst</li>
  • -</ul><h5>Histology</h5><p>There are no specific histological features to differentiate between ameloblastomas and <a href="/articles/craniopharyngioma">craniopharyngiomas</a>, with only location differentiating between two tumours <sup>6</sup>.</p><h4>Radiographic features</h4><h5>Panoramic radiograph and CT</h5><p>It is classically seen as a multiloculated (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.</p><h5>MRI</h5><p>In general, ameloblastomas demonstrate a mixed solid and cystic pattern, with a thick irregular wall, often with solid papillary structures projecting into the lesion. These components tend to enhance vividly.</p><h4>Treatment and prognosis</h4><p>Ameoloblastomas tend to be treated by surgical en-bloc resection. Local curettage is associated with a high rate of local recurrence (45-90%).</p><p>Simple unilocular lesions are less common but have a better prognosis. Simple (no nodule) variant will not be diagnosable on radiography, as it will be indistinguishable from 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.</p><p>Malignant behaviour is seen in two forms <sup>5</sup>:</p><ol>
  • +<span style="line-height:1.6">luminal </span>variant,<span style="line-height:1.6"> has a single nodule projecting into the cyst</span>
  • +</li>
  • +<li>mural<span style="line-height:1.6"> variant has multiple nodules (often only microscopic) in the wall of the cyst. The latter has an elevated risk of recurrence</span>
  • +</li>
  • +</ul><p>Malignant behaviour is seen in two forms <sup>5</sup>:</p><ol>

References changed:

  • 7. Plunk M, Oda D, Parnell S, Wright J, Cole B, Iyer R. Focal Benign Disorders of the Pediatric Mandible With Radiologic-Histopathologic Correlation: Mandibular Development and Lucent Lesions. AJR Am J Roentgenol. 2017;208(1):180-92. <a href="https://doi.org/10.2214/ajr.16.16587">doi:10.2214/ajr.16.16587</a> - <a href="https://www.ncbi.nlm.nih.gov/pubmed/27762604">Pubmed</a>

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