Odontogenic Tumors and Ameloblastoma

Odontogenic Tumors

• Tumors originating from odontogenic epithelium and/or ectomesenchyme
• Classified based on tissue of origin: epithelial, ectomesenchymal, or mixed

Ameloblastoma

• Benign epithelial tumor with persistent, aggressive growth
• Derived from enamel organ

2022 WHO Classification of Ameloblastoma

• Conventional ameloblastoma
• Unicystic ameloblastoma
• Extraosseous (peripheral) ameloblastoma

Conventional Ameloblastoma: Clinical Features

• Accounts for about 80% of all ameloblastomas
• Most common in the 4th and 5th decades of life
• More common in mandible (85%), especially posterior body and ramus
• Causes slow, painless buccal/lingual expansion

Ameloblastoma: Radiographic Features

• Solitary lesions usually arising in alveolar process; can be pericoronal
• Well-defined, corticated, irregular radiolucency, ranging from 1 to 10 cm or larger
• May be unilocular, especially when small, or multilocular
• Exhibits multilocular pattern with coarse trabeculae

Ameloblastoma: Radiographic Effects

• Irregular outlines, causes expansion, and eventually resorbs cortex
• Root resorption and tooth displacement are common
• Can cause displacement of the inferior alveolar canal (IAC)

Ameloblastoma: Differential Diagnosis

• Odontogenic cysts such as OKC (odontogenic keratocyst)
• Lateral periodontal cysts.

Ameloblastoma: Histologic Features

• Displays at least six histologic patterns
• Follicular pattern is most common
• Islands of odontogenic epithelium composed of tall columnar peripheral cells resembling ameloblasts
• Delicate spindle cells resembling stellate reticulum are found in the center of the islands

Ameloblastoma: Treatment and Prognosis

• Requires wide excision, with resection for large lesions with wide surgical margins
• Locally infiltrative in trabecular bone
• Recurrence is common

Unicystic Ameloblastoma

• Arises in the epithelium of an odontogenic cyst, or de novo as a neoplasm
• Represents 15% of all ameloblastomas
• Characterized as a grossly cystic lesion

Unicystic Ameloblastoma: Clinical Features

• Occurs most often in the 2nd or 3rd decade of life, typically affects a younger population than other ameloblastomas
• Located in the mandible in over 90% of instances, mostly posterior
• Most cases are asymptomatic
• Large lesions can expand the jaw

Unicystic Ameloblastoma: Radiographic Features

• Often pericoronal in location
• Features well-defined, corticated round or oval radiolucency
• Typically unilocular, it represents the cyst's solitary cystic makeup
• Causes displacement of teeth or other structures, root resorption, and cortical resorption

Unicystic Ameloblastoma: Differential Diagnosis

• Includes dentigerous cysts when pericoronal
• Includes other odontogenic cysts like OKC and orthokeratinized odontogenic cysts

Unicystic Ameloblastoma: Histologic Features

• Features a cyst-like cavity lined by odontogenic epithelium
• Displays basal columnar cells resembling ameloblasts
• Demonstrates overlying delicate spindle cells resembling stellate reticulum

Unicystic Ameloblastoma: Treatment and Prognosis

• Enucleation may be successful
• Wider excision might be needed in some cases
• Generally requires more conservative surgery compared to ameloblastoma
• Has a lower recurrence rate than ameloblastoma

Extraosseous Peripheral Ameloblastoma

• Variant consisting of soft tissue
• Accounts for 1% of all ameloblastomas
• Develops from gingival odontogenic epithelial residues
• May also arise from basal cells of surface epithelium.

Extraosseous Peripheral Ameloblastoma: Clinical Features

• Usually manifests in middle age, with an average occurrence around age 52
• Presents as a painless, either sessile or pedunculated, mass on the gingiva
• Most frequently found in the posterior mandible

Extraosseous Peripheral Ameloblastoma: Differential Diagnosis

• Includes peripheral soft tissue lesions like peripheral ossifying fibroma, peripheral giant cell granuloma, and peripheral fibroma
• Considers gingival cysts of adults.

Extraosseous Peripheral Ameloblastoma: Histologic Features

• Exhibits similarities to intrabony ameloblastoma.
• Presents a connection to the surface epithelium in 50% of cases

Extraosseous Peripheral Ameloblastoma: Treatment and Prognosis

• Requires conservative excision, with a recurrence rate between 15% and 20%
• Recurrence is rare following a second surgery
• Significantly better prognosis compared to intrabony ameloblastoma

Calcifying Epithelial Odontogenic Tumor (CEOT) (Pindborg Tumor)

• Benign odontogenic tumor resembling ameloblastoma in clinical and radiographic appearance
• Derived from enamel organ
• Named after Dr. Jens Pindborg
• CEOT Clinical Features

CEOT: Clinical Features

• Shares similarities with ameloblastoma; including adults in their 4th and 5th decades are commonly affected
• Predominantly occurs in the mandible in 75% of the cases, especially in the molar-ramus area
• Results in slow, painless enlargement of the jaw
• Causes prominent buccal-lingual expansion

CEOT: Radiographic Features

• Solitary alveolar process lesions, 50% pericoronal
• Well-defined unilocular or multilocular lesion, often corticated
• May appear radiolucent, radiolucent with radiopaque foci, or radiopacities clustered around the crown in pericoronal lesions
• Exhibits cortical expansion and resorption and root resorption and displacement

CEOT: Radiographic Patterns

• Exhibits a "driven snow" radiographic pattern

CEOT: Differential Diagnosis

• Radiolucent types are similar to ameloblastoma or odontogenic cysts and tumors
• Dentigerous cysts should be considered if pericoronal
• Radiolucent/radiopaque variants include COC (Gorlin cyst) and other mixed odontogenic lesions

CEOT: Histologic Features

• Sheets of large, polygonal eosinophilic cells
• Pleomorphic with large, benign nuclei
• Characterized by concentric calcifications (Liesegang rings)
• Presence of amyloid-like material in many lesions, which stains with Congo red and thioflavin T

CEOT: Treatment and Prognosis

• Requires conservative excision or resection for large lesions
• Generally has a better prognosis than ameloblastoma.

Adenomatoid Odontogenic Tumor (AOT)

• Benign odontogenic tumor of epithelial origin
• Originates in enamel organ
• Epithelial cells form patterns resembling glandular tumors

AOT: Clinical Features

• Occurs mostly in the 1st and 2nd decades of life, rare after age 30
• More common in females (2:1 female to male ratio)
• Occurs mostly in the maxilla, usually anterior

AOT: Clinical Features

• Most lesions are small, less than 3.0 cm
• Larger lesions can cause buccal-lingual expansion
• Usually asymptomatic

AOT: Radiographic Features

• Solitary, 75% are pericoronal
• Presents well-defined, often corticated unilocular lesion, varying in size
• Usually completely radiolucent, but may contain small radiopaque foci
• Pericoronal lesions often engulf most of the tooth, extending apically past cemento-enamel junction, distinguishing it from dentigerous cyst
• Causes displacement of teeth and other structures, as well as root resorption

AOT: Differential Diagnosis

• Radiolucent cases may resemble dentigerous cysts (if pericoronal), OKC, and unicystic ameloblastoma
• Radiolucent cases with radiopaque foci are similar to CEOT (Pindborg) and COC (Gorlin)

AOT: Histologic Features

• Columnar or cuboidal cells that form duct-like structures
• Spindle-shaped epithelial cells arranged in whorls or sheets
• Amorphous material similar to amyloid is often present
• Bone and other calcifications can form

AOT: Treatment and Prognosis

• Enucleation is typically sufficient due to the presence of a thick capsule
• Excellent prognosis, with very rare recurrence

Primary Intraosseous Carcinoma of the Jaws

• Sometimes termed odontogenic carcinoma
• Carcinoma in jaws with no association to oral or skin epithelium
• Can originate de novo or in pre-existing cysts or tumors
• Residual radicular cysts and dentigerous cysts are the most likely sources
• Mucoepidermoid carcinomas can arise from the mucus cells in dentigerous cysts

Primary Intraosseous Carcinoma of the Jaws: Clinical Features

• Mostly found in older adults
• Presents asymptomatic, or causes pain and swelling

Primary Intraosseous Carcinoma of the Jaws: Radiographic and Histologic Features

• Radiographically presents as radiolucency with an irregular, ragged periphery
• Histologically defined as a Squamous cell carcinoma arising in epithelial lining
• Mucoepidermoid carcinoma arising in dentigerous cysts may be present

Primary Intraosseous Carcinoma of the Jaws: Treatment and Prognosis

• Requires Resection, with or without chemotherapy and/or radiation
• Prognosis is generally uncertain
• 5-year survival rate is ~50%

Cementoblastoma: Clinical Features

• Benign odontogenic tumor of cementoblasts
• Occurs mostly in the late teens to early twenties
• Found in the mandible in 75% of cases, with 90% located in the molar/premolar region
• Located in the mandibular first molar
• Causes pain and swelling in many cases

Cementoblastoma: Radiographic Features

• Solitary lesion attached to tooth root
• Most commonly affects the 1st molar
• Calcified mass attaches to tooth root, obliterating its outline
• Radiopacity is often lobular or radiating
• Peripheral radiolucency
• Usually at least 1 cm in size
• Causes displacement of teeth and other structures, along with root resorption

Cementoblastoma: Histologic Features

• Sheets and trabeculae of cementum fused to root with irregular lacunae
• Multinucleated cells and blast cells line the trabeculae
• Cellular fibrovascular connective tissue present between trabeculae

Cementoblastoma: Treatment and Prognosis

• Extraction of tooth and attached tumor
• Prognosis is excellent if the lesion is completely removed

Odontogenic Myxoma

• Benign odontogenic tumor of ectomesenchymal origin
• Resembles developing tooth microscopically

Odontogenic Myxoma: Clinical Features

• Occurs mostly in young adults
• Occurs slightly more often in the mandible
• Occurs to equal extents in anterior and posterior regions

Odontogenic Myxoma: Clinical Features

• Slow, painless expansion
• Can sometimes grow rapidly due to accumulated ground substance
• Can cause displacement of teeth and root resorption

Odontogenic Myxoma: Radiographic Features

• Solitary lesion in the alveolar process
• Shows well-defined unilocular or multilocular irregular radiolucency
• May have delicate trabeculae and a "honeycomb" pattern
• Can become very large
• Resorption and expansion of the cortex can be significant

Odontogenic Myxoma: Differential Diagnosis

• Involves other odontogenic cysts such as OKC
• Mimics odontogenic tumors, such as Ameloblastoma, CEOT

Odontogenic Myxoma: Histologic Features

• Features delicate, myxomatous connective tissue with a ground substance matrix
• Consists mostly of hyaluronic acid and chondroitin sulfate
• Exhibits scanty numbers of spindle-shaped fibroblasts
• Has no capsule
• Resembles of dental papilla

Odontogenic Myxoma: Treatment and Prognosis

• Curettage for small lesions; excision for larger lesions
• Slimy, gelatinous nature of lesion makes complete removal difficult

Ameloblastic Fibroma

• Benign tumor of epithelial and ectomesenchymal odontogenic tissue

Ameloblastic Fibroma: Clinical Features

• Occurs mostly in the 1st and 2nd decades of life
• Occurs equally in males and females
• Mostly found in posterior mandible or maxilla
• Asymptomatic presentation is common
• Larger lesions can expand the jaw

Ameloblastic Fibroma: Radiographic Features

• Location: Solitary lesion, 75% are pericoronal
• Observations: Well-defined often corticated radiolucency, variable size
• Can be unilocular or multilocular
• General effects: Large lesions can extend into ramus and body; and also cause tooth displacement and root resorption, as well as the displacement of other structures

Ameloblastic Fibroma: Differential Diagnosis

• Considers conditions such as Dentigerous cyst (if pericoronal)
• Involves considering that OKC and AOT also occur in younger patients
• Ameloblastoma.

Ameloblastic Fibroma: Histologic Features

• Displays cords and islands of cuboidal odontogenic epithelium that resembles Ameloblastoma in the background of a fibrous stroma
• Exhibits delicate tissue containing mesenchymal cells, similar to dental papilla

Ameloblastic Fibroma: Treatment and Prognosis

• Conservative excision is usually adequate
• Wider excision can be performed for recurrences
• Exhibits rare transformation into ameloblastic fibrosarcoma

Odontoma

• Benign odontogenic lesion of ectodermal and ectomesenchymal origin
• Represent a hamartoma rather than a true neoplasm
• Produces dental tissues (enamel, dentin, pulp)
• Most common odontogenic "tumor"

Odontoma: Two Forms

• Compound
• Complex

Odontoma: Clinical Features

• Occur in the 1st and 2nd decades of life.
• Commonly found positioned around the crown of a tooth (pericoronal)
• Exhibits enlargement of the alveolar process

Odontoma: Compound

• Primarily found within the anterior region of the maxilla
• Characterized by the production of enamel, dentin, and pulp, arranged to form small, teeth-like structures

Odontoma: Complex

• Located in the posterior mandible or maxilla
• Consists of dental tissues arranged in a jumbled, amorphous mass without discrete tooth forms

Odontoma: Radiographic Features

• Compound type shows multiple small tooth structures with normal dental tissue arrangement and a radiolucent periphery
• Complex type presents as an amorphous radiopaque mass with a radiolucent periphery

Odontoma: Differential Diagnosis

• Well-developed odontomas are usually pathognomonic

Odontoma: Histologic Features

• Consist of mature enamel matrix, dentin, cementum, dental pulp organized or dysorganized, in the form of teeth or a shapeless mass
• Features Delicate fibrous connective tissue

Odontoma: Treatment and Prognosis

• Includes a simple Excision; lesion usually shells out due to a peripheral fibrous connective tissue capsule, so is straightforward to perform and remove
• Excellent prognosis; recurrences are quite rare

This lesson covers odontogenic tumors, focusing on ameloblastoma. It discusses the classification, clinical features, and radiographic features of ameloblastoma according to the 2022 WHO classification, including conventional, unicystic, and extraosseous types.