Ameloblastoma

Ameloblastic Carcinoma

Age

Wide age range, peak in fourth to fifth decades

Most cases arise in adults, with peak in fifth to sixth decades

Location

Gnathic bones, most often posterior mandible

Gnathic bones, most often posterior mandible. Cases may arise de novo or in association with preexisting ameloblastoma

Symptoms

Slowly growing painless mass, eventually causing facial deformity, loose teeth, or even airway obstruction

Facial swelling, pain, trismus

Signs

Classic radiologic appearance is a multilocular (“soap bubble” or “honeycomb”) radiolucency

Aggressive radiographic appearance with cortical plate expansion and invasion of nearby tissues

Etiology

Unknown

Unknown

Histology

1. 
   

   Islands, and/or anastomosing cords of cells

   
   
2. 
   

   Peripheral layer of palisading columnar cells. The nuclei are hyperchromatic and polarized away from the basement membrane (reverse polarity). Subnuclear cytoplasmic vacuoles are common (Figs. 2.1.1 and 2.1.2)

   
   
3. 
   

   Central stellate cells are loosely arranged and resemble the stellate reticulum of the developing tooth (Fig. 2.1.2). The stellate cells may show varying degrees of squamous (acanthomatous) or granular change

   
   
4. 
   

   Tumor nests may become cystic

   
   
5. 
   

   Mitotic figures are absent or only rarely encountered. No atypical mitotic figures. No necrosis

1. 
   

   Can exhibit any of the growth patterns seen in benign ameloblastoma including solid islands and anastomosing cords

   
   
2. 
   

   At least focally exhibit some ameloblastic features including peripheral palisading of columnar cells (Fig. 2.1.3)

   
   
3. 
   

   Malignant cytologic features that include one or more of the following (Fig. 2.1.4):

   
   
   
   
   • 
     

     Cellular pleomorphism

     
     
   • 
     

     Nuclear hyperchromasia

     
     
   • 
     

     Increased nuclear: cytoplasmic ratio

     
     
   • 
     

     Elevated mitotic rate

     
     
   • 
     

     Atypical mitotic figures

     
     
   • 
     

     Vascular or perineural invasion

Special studies

Immunohistochemistry is not helpful in this differential diagnosis. Most harbor mutations in genes of the MAPK pathway, most frequently BRAF V600E

Immunohistochemistry is not helpful in this differential diagnosis. Some cases harbor p53 mutations

Treatment

Complete resection with a margin of normal bone

Wide resection with a margin of normal bone. Adjuvant radiation therapy is sometimes employed

Prognosis

Benign neoplasm, but with high rate of recurrence, especially after conservative therapy. Rare cases transform into ameloblastic carcinomas, or metastasize without malignant histologic features (“malignant ameloblastoma”)

Five-year survival is approximately 70%. Recurrences in approximately 30%, metastases (usually lung) in approximately 20%-30%

Ameloblastoma

Ameloblastic Fibroma

Age

Wide age range, peak in fourth to fifth decades

Primarily affects children (mean age, 15 years)

Location

Gnathic bones, most often posterior mandible

Gnathic bones, most often posterior mandible

Symptoms

Slowly growing painless mass, eventually causing facial deformity, loose teeth, or even airway obstruction

Slowly growing painless mass

Signs

Classic radiologic appearance is a multilocular (“soap bubble” or “honeycomb”) radiolucency (Fig. 2.2.1)

Smooth bordered radiolucency, often associated with an unerupted tooth (Fig. 2.2.5)

Etiology

Unknown

Unknown

Histology

1. 
   

   Islands, and/or anastomosing cords of cells (Fig. 2.2.2)

   
   
2. 
   

   Peripheral layer of palisading columnar cells. The nuclei are hyperchromatic and polarized away from the basement membrane (reverse polarity). Subnuclear cytoplasmic vacuoles are common (Fig. 2.2.2)

   
   
3. 
   

   Central stellate cells are loosely arranged and resemble the stellate reticulum of the developing tooth (Fig. 2.2.3). The stellate cells may show varying degrees of squamous (acanthomatous) or granular change (Fig. 2.2.4)

   
   
4. 
   

   Tumor nests may become cystic

   
   
5. 
   

   Stroma is delicately fibrillary to densely collagenized (Fig. 2.2.4)

1. 
   

   Nests and/or strands of ameloblastic epithelium essentially identical to ameloblastoma (Figs. 2.2.6, 2.2.7 and 2.2.8)

   
   
2. 
   

   Mesenchymal tumor component consisting of primitive-appearing stroma with bipolar to stellate fibroblasts in a myxoid background (resembling dental papilla of developing tooth) (Figs. 2.2.6, 2.2.7 and 2.2.8)

   
   
3. 
   

   May also encounter dentin (i.e., ameloblastic fibrodentinoma) or other tooth parts (i.e., ameloblastic fibro-odontoma) (Fig. 2.2.9)

Special studies

Immunohistochemistry is not helpful in this differential diagnosis. Most harbor mutations in genes of the MAPK pathway, most frequently BRAF V600E

Immunohistochemistry is not helpful in this differential diagnosis. Some cases are reported to harbor BRAF V600E mutation

Treatment

Complete resection with a margin of normal bone

Conservative, with enucleation and curettage only

Prognosis

Benign neoplasm, but with high rate of recurrence, especially after conservative therapy. Rare cases transform into ameloblastic carcinomas, or metastasize without malignant histologic features (“malignant ameloblastoma”)

Recurrences are uncommon

Ameloblastoma

Calcifying Odontogenic Cyst (Gorlin Cyst)

Age

Wide age range, peak in fourth to fifth decades

Wide age range, peaking in second to third decades

Location

Gnathic bones, most often posterior mandible

Maxilla or mandible, usually anterior

Symptoms

Slowly growing painless mass, eventually causing facial deformity, loose teeth, or even airway obstruction

Usually asymptomatic

Signs

Classic radiologic appearance is a multilocular (“soap bubble” or “honeycomb”) radiolucency (Fig. 2.3.1)

Well-demarcated radiolucency with a corticated border that may be unilocular or multilocular, and may show mineralization (Fig. 2.3.3)

Etiology

Unknown

Unclear whether it is a neoplasm or developmental cyst

Histology

1. 
   

   Islands, and/or anastomosing cords of cells

   
   
2. 
   

   Peripheral layer of palisading columnar cells. The nuclei are hyperchromatic and polarized away from the basement membrane (reverse polarity). Subnuclear cytoplasmic vacuoles are common (Fig. 2.3.2)

   
   
3. 
   

   Central stellate cells are loosely arranged and resemble the stellate reticulum of the developing tooth. The stellate cells may show varying degrees of squamous (acanthomatous) or granular change

   
   
4. 
   

   Tumor nests may become cystic

   
   
5. 
   

   Stroma is delicately fibrillary to densely collagenized

   
   
6. 
   

   No ghost cells

1. 
   

   Variably cystic and solid epithelial proliferation (Fig. 2.3.4)

   
   
2. 
   

   Epithelial component exhibits ameloblastic features including a peripheral layer of polarized cells and a loose central zone that resembles stellate reticulum (Fig. 2.3.5)

   
   
3. 
   

   Variably numbers of ghost cells—epithelial cells that retain their cellular outline, exhibit bright eosinophilic cytoplasm, and lack nuclei (Fig. 2.3.6)

   
   
4. 
   

   Ghost cells frequently undergo calcification

Special studies

Immunohistochemistry is not helpful in this differential diagnosis. Most harbor mutations in genes of the MAPK pathway, most frequently BRAF V600E

Immunohistochemistry is not helpful in this differential diagnosis

Treatment

Complete resection with a margin of normal bone

Enucleation

Prognosis

Benign neoplasm, but with high rate of recurrence, especially after conservative therapy. Rare cases transform into ameloblastic carcinomas, or metastasize without malignant histologic features (“malignant ameloblastoma”)

Excellent. Recurrences are rare

Dental Follicle

Dentigerous Cyst

Age

A normal structure during tooth development enveloping the developing tooth. Usually encountered in patients in their second decade

Any age, most commonly young males (second to fourth decades)

Location

Usually encountered in the mandible in association with an impacted third molar

Associated with an impacted tooth. Third molars most common (mandibular > maxillary)

Symptoms

None. Often encountered in association with impacted tooth

Usually discovered incidentally

Signs

Thin semicircular radiolucency associated with crown of unerupted tooth. Usually small, but can become large, mimicking a dentigerous cyst (Fig. 2.4.1)

Well-demarcated radiolucency associated with crown of unerupted tooth (Fig. 2.4.4)

Etiology

Normal structure

Accumulation of fluid between the crown of the tooth and the surrounding dental follicle

Histology

1. 
   

   Cystic structure partially lined by eosinophilic, cuboidal reduced enamel epithelium (Figs. 2.4.2 and 2.4.3)

   
   
2. 
   

   No squamous epithelial lining

   
   
3. 
   

   Variably fibrous to loose, myxoid stroma (Figs. 2.4.2 and 2.4.3)

   
   
4. 
   

   Scattered odontogenic rests often seen (Figs. 2.4.2 and 2.4.3)

1. 
   

   Cyst lined by thin layer of flattened stratified cells that often transitions into a thickened nonkeratinized squamous epithelium in areas of inflammation (Figs. 2.4.5 and 2.4.6)

   
   
2. 
   

   Foci of transition with reduced enamel epithelium may occur

   
   
3. 
   

   Fibromyxoid stroma is not prominent

   
   
4. 
   

   Scattered odontogenic rests may be seen

Special studies

None

None

Treatment

None

Removal of involved tooth with curettage of cystic lining

Prognosis

Not applicable

Good. May recur if incompletely excised. Rarely may give rise to other odontogenic tumors