Odontogenic Tumors: Classification and Types

Odontogenic Tumors Overview

• Odontogenic tumors originate from the odontogenic epithelium and/or ectomesenchyme.
• Outer enamel epithelium, stellate reticulum, stratum intermedium, inner enamel epithelium, dental papilla and dental follicle are involved.
• They can be classified based on tissue origin.

Tissue of Origin

• Epithelial-only tumors include ameloblastoma, calcifying epithelial odontogenic tumor (CEOT), adenomatoid odontogenic tumor (AOT), and primary intraosseous carcinoma of the jaws.
• Ectomesenchymal-only tumors include cementoblastoma and odontogenic myxoma.
• Epithelial and ectomesenchymal tumors include ameloblastic fibroma and odontoma.

Ameloblastoma

• An ameloblastoma is a benign epithelial tumor that commonly does not kill you but will cause a lot of deformity.
• It is derived from the enamel organ and exhibits a persistent, aggressive growth pattern.
• There are three types according to the 2022 WHO classification, conventional, unicystic, and extraosseous/peripheral.

Conventional Ameloblastoma: Clinical & Radiographic Features

• Conventional type comprises approximately 80% of ameloblastomas.
• It typically occurs in the 4th and 5th decades of life, with a wide age range.
• 85% are found in the mandible, predominantly in the posterior body and ramus.
• Expands slowly and painlessly in the buccal/lingual dimension, distal to the 1st molar.
• Radiographically, it appears as a solitary lesion in the alveolar process, either unilocular or multilocular, with well-defined, corticated, irregular radiolucency, usually 1 to 10 cm or larger.
• General radiographic effects include an irregular outline, expansion and resorption of the cortex, root resorption, tooth displacement, and displacement of the inferior alveolar canal (IAC).

Ameloblastoma: Differential Diagnosis & Histologic Features

• Odontogenic cysts are an important consideration in the differential diagnosis.
• OKC don't tend to cause buccal/lingual expansion, unlike ameloblastomas.
• Lateral periodontal cysts are unilocular and confined next to the root of a tooth
• Histologically, ameloblastomas exhibit at least six patterns, with the follicular pattern being the most common.
• Characterized by islands of odontogenic epithelium containing tall columnar peripheral cells resembling ameloblasts, and delicate spindle cells resembling stellate reticulum in the center of the islands.
• Closely resembles the enamel organ on a microscopic level.

Ameloblastoma: Treatment & Prognosis

• Treatment of this tumor involves wide excision/resection for large lesions with wide surgical margins.
• It tends to be locally infiltrative in trabecular bone.
• Therefore, it has a common rate of recurrence.
• Recognizing the tumor early is advantageous because that allows the surgery to be more minimal.

Unicystic Ameloblastoma

• Arises in the epithelium of an odontogenic cyst or de novo as a neoplasm.
• Accounts for 15% of all ameloblastomas.
• Presents as a grossly cystic lesion in younger patients/2nd to 3rd decade.
• More than 90% occur in the mandible, typically in the posterior region.
• Most cases are asymptomatic, but large lesion can result in jaw expansion.
• Radiographically, the lesion is often pericoronal, well-defined, corticated round or oval radiolucency.
• The nature of the lesion is unilocular and represents a solitary cyst.

Unicystic Ameloblastoma: Radiographic & Histologic Features

• Radiographic features include displacement of teeth or other structures, root resorption, and cortical resorption.
• Behavior is similar to conventional ameloblastoma, but is not as aggressive.
• Dentigerous cyst needs to be considered in the differential diagnosis, as well as others
• Histologically, unicystic ameloblastoma exhibits a cyst-like cavity lined by odontogenic epithelium. Basal columnar cells resemble ameloblasts with delicate spindle cells that resemble stellate reticulum.

Unicystic Ameloblastoma: Treatment & Prognosis

• Treatment involves enucleation, which is often successful
• Wider excision may additionally be necessary
• Surgery is relatively conservative .
• Lesion has less common rate of recurrence in comparison to ameloblastoma.

Extraosseous/Peripheral Ameloblastoma

• This is a soft tissue variant of ameloblastoma and accounts for 1% of all ameloblastomas.
• Typically arises from odontogenic epithelial rests in gingiva, or basal cells of surface epithelium.
• Usually occurs in middle-aged individuals around age 52.
• Manifests as a painless pedunculated or sessile mass on the gingiva, most commonly on the posterior mandible.
• X-rays show very little since it is present in the soft tissue.
• Must rule out gingival cyst of an adult, an soft tissue analog of a lateral periodontal cyst.

Extraosseous/Peripheral Ameloblastoma: Histologic Features, Treatment & Prognosis

• Histologically, Extraosseous/Peripheral Ameloblastoma resembles intrabony ameloblastoma.
• A connection to the surface epithelium is evident in 50% of cases.
• Treatment is through conservative excision with a recurrence rate of 15–20%.
• These exhibit a much better prognosis than intrabony ameloblastomas.

Calcifying Epithelial Odontogenic Tumor (CEOT)

• Refers to Pindborg Tumor, a benign odontogenic tumor resembling ameloblastoma in clinical and radiographic appearance.
• Derived from enamel organ.
• The clinical manifestations can sometimes be just as big as ameloblastomas.

CEOT: Clinical & Radiographic Features

• Exhibits similarities to ameloblastoma clinically.
• Occurs most commonly in adults during the 4th and 5th decades of their lives.
• The majority are found in mandible, the molar-ramus area in an adults
• Presents as a slow, painless enlargement of the jaw and buccal-lingual expansion.

CEOT: Radiographic Features

• Solitary lesion in alveolar process, 50% pericoronal.
• Well-defined unilocular or multilocular lesion, often is corticated.
• Appearance may be radiolucent only or radiolucent with radiopaque foci.
• Radiopacities may cluster around the crown in pericoronal lesions.
• General effects include cortical expansion and resorption, and root resorption and displacement.

CEOT: Radiographic & Differential Diagnosis

• A mixed radiolucent/radiopaque pattern makes it harder to distinguish it from ameloblastoma
• A "driven snow" pattern may be observed.
• In the differential diagnosis, radiolucent CEOT resembles ameloblastoma and other odontogenic cysts,
• Consider dentigerous cyst if pericoronal.

CEOT: Histologic Features & Therapy

• Histologically, CEOT features sheets of large, polygonal eosinophilic cells that are pleomorphic with large but benign nuclei.
• Concentric calcifications (Liesegang rings) and amyloid-like material frequently occurs
• Conservative excision is sufficient with resection for large lesions, which allows for a much better results than in ameloblastoma cases.

Adenomatoid Odontogenic Tumor (AOT)

• This is a benign odontogenic tumor of epithelial origin, similar to, and often resembling a gland.
• Originates from enamel organ and made of epithelial cells forming patterns resembling glandular tumors.

AOT: Clinical Features

• It most often occurs in the 1st and 2nd decades of life, and is very rare after age 30, more often in females in the anterior maxilla.
• Most lesions are small (less than 3 cm).
• Large lesions can cause expansion.
• Usually asymptomatic.

AOT: Radiographic & Differential Diagnosis

• Radiographically, seen as solitary unilocular lesion that are 75% pericoronal and well-defined
• Consists of small radiopaque foci; lesion often engulfs most of tooth extending beyond past cemento-enamel junction, differing from dentigerous cyst.
• As it expands it can displace teeth, resorb roots
• Some diagnostic considerations includes dentigerous cyst & unicystic ameloblastoma

AOT: Histological Features & Prognosis

• Has histological features which include columnar/cuboidal cells which form duct-like structures
• These structures are lined by columnar cells
• Contains spindle-shaped epithelial cells in whorls or sheets

Primary Intraosseous Carcinoma of the Jaws

• Also referred to an odontogenic carcinoma.
• A carcinoma that has no connection to the oral or skin epithelium.
• Can arise de novo or pre-existing from a cyst or tumor.
• Residual radicular cysts and dentigerous cysts are the most likely sources.
• Mucoepidermoid carcinomas may occur if mucus cells arise from dentigerous cysts.
• Mostly in older adults, most in men.
• Usually asymptomatic, but as the lesions get larger, they may cause pain and swelling.
• Radiographically, it shows a radiolucency with an irregular ragged periphery.
• The histological results will show a squamous cell arising in epithelial lining.
• Often arises de novo within lining of a cyst wall.
• Treatment includes Resection, with or without chemotherapy.
• This has a generally poor prognosis with a approximately 50% survive past 5 years.

Cementoblastoma

• This tumor is derived only from ectomesenchyme.
• Consists of a benign odontogenic lesion of cementoblasts that affect the dentin and tooth follicle.
• Large majority in late teens, early 20s.
• 75% is in mandible; 90% is in molar/premolar on mandibular first molar.
• Swelling and near pain with tooth contact of affected tooth.

Cementoblastoma: Radiographic & Histologic Features

• Solitary lesion attached to a tooth root; most commonly affect 1st molar.
• Calcified mass is attached to tooth root with obliteration of the root outline
• Usually will measure at least 1 cm.
• Radiopacity is often lobular or radiating with peripheral peripheral radioolucency
• Is often seen in patients in their late teens to early 20's
• General effects: displacement of teeth and other structures, root resorption.
• Histologic features include the observation of: Sheets/trabeculae of cementum, fused to the root with irregular lacunae. Multinucleated/blast cells line trabeculae. Cellular fibrovascular connective tissue between trabeculae.

Cementoblastoma: Treatment

• Extraction of the tooth and the associated tumor is performed.
• There's a 10 percent recurrence seen in this odontogenic tumor.

Odontogenic Myxoma

• Refers to a benign odontogenic tumor originating from ectomesenchyme.
• Resembles a developing tooth microscopically.
• Most occur in young adults, mean age 25-30.
• More common in mandible and found equally in anterior and posterior.

Odontogenic Myxoma: Clinical & Radiographic Details

• They start as slow, painless expansion that grows rapidly with time.
• Can cause displacement of teeth and root resorption.
• Radiographic properties include the detection as a solitary lesion of either unilocular or multilocular irregular radiolucency
• Often, there are delicate trebecular features, such as honeycomb pattern, that grow quite large and result in displacement of teeth or roots
• Doesnt tend to cause expansion.

Odontogenic Myxoma: Histological Features

• Comprised predominately of a delicate myxomatous connective tissue surrounded by ground substance matrix including mainly hyaluronic acid and chondroitin sulfate
• Scanty numbers of spindle-shaped fibroblasts exist but there is no internal capsule
• Due to its slimy gelatinous formation, complete lesion difficult to remove Resembles a dental papilla due to its ground substance/scant spindles

Ameloblastic Fibroma: Tumor Details

• Is a benign tumor of epithelial and ectomesenchymal.
• Most occur in 1st and 2nd decades with Children.
• Found equally in males and females; and is mostly found in posterior mandible (molar-ramus area)
• Usually asymptomatic and Larger lesions can expand the jaw.

Ameloblastic Fibroma: Radiographic Features

• Appears as a solitary lesion and 75% are pericoronal
• Well-defined, corticated radiolucency with variable size
• Can appear as unilocular or multilocular in appearance.
• Large lesions can extend into the ramus and body of the mouth
• General characteristics include tooth displacement, as well as resorption.
• Usually easy to extract the affected tumor because of its location.

Ameloblastic Fibroma: Histologic Features and Prognosis

• Histologically one can see Cords and islands of cuboidal odontogenic epithelium similar to ameloblastoma
• Another key feature is the Fibrous stroma of delicate tissue with mesenchymal cells resembling dental papilla
• Treatment is via conservative, which is usually very effective
• If there's rare recurrences, there is a chance that it can grow rare transformation into ameloblastic fibrosarcoma

Odontoma: Tumor Details & Forms

• Denotes a benign odontogenic lesion consisting of the following cells types ectodermal and ectomesenchymal.
• Not a true mass, more like a type of tooth growth
• Produces dental cells
• This odontogenic mass occurs in two separate forms: Compound, being that this produces enamel, dentin and pulp Complex, which is posterior mandible or the maxilla,
• Both forms occur in 1st and 2nd decades and forms at the same time during tooth growth.