Dental Pathology Quiz

Odontogenic Tumors

• Odontogenic tumors can be classified into benign and malignant types
• Benign odontogenic tumors include:
  • Mesenchymal origin: odontogenic fibroma, odontogenic myxoma/myxofibroma, cementoblastoma
  • Mixed (epithelial-mesenchymal) origin: ameloblastic fibroma, primordial odontogenic tumor, odontoma (complex type), odontoma (compound type), dentinogenic ghost cell tumor
  • Epithelial origin: ameloblastoma, ameloblastoma (unicystic type), ameloblastoma (extraosseous/peripheral type), metastasizing (malignant) ameloblastoma, squamous odontogenic tumor, calcifying epithelial odontogenic tumor, adenomatoid odontogenic tumor

Malignant Odontogenic Tumors

• Malignant odontogenic tumors include:
  • Odontogenic carcinomas:
    • Metastasizing (malignant) ameloblastoma
    • Ameloblastic carcinoma – primary type
    • Ameloblastic carcinoma – secondary type (intraosseous)
    • Ameloblastic carcinoma – secondary type (peripheral)
    • Primary intraosseous squamous cell carcinoma – solid type
    • Primary intraosseous squamous carcinoma derived from keratocystic odontogenic tumor
    • Primary intraosseous squamous cell carcinoma derived from odontogenic cysts
    • Clear cell odontogenic carcinoma
    • Ghost cell odontogenic carcinoma
  • Odontogenic sarcomas:
    • Ameloblastic fibrosarcoma
    • Ameloblastic fibro-dentino and fibro-odontosarcoma

WHO Classification of Odontogenic Tumors (2017)

• Benign odontogenic tumors:
  • Epithelial origin: ameloblastoma, ameloblastoma (unicystic type), ameloblastoma (extraosseous/peripheral type), metastasizing (malignant) ameloblastoma, squamous odontogenic tumor, calcifying epithelial odontogenic tumor, adenomatoid odontogenic tumor
  • Mixed (epithelial-mesenchymal) origin: ameloblastic fibroma, primordial odontogenic tumor, odontoma (complex type), odontoma (compound type), dentinogenic ghost cell tumor
  • Mesenchymal origin: odontogenic fibroma, odontogenic myxoma/myxofibroma, cementoblastoma
• Malignant odontogenic tumors:
  • Ameloblastic carcinoma
  • Primary intraosseous carcinoma, NOS
  • Sclerosing odontogenic carcinoma
  • Clear cell odontogenic carcinoma
  • Ghost cell odontogenic carcinoma
  • Odontogenic carcinosarcoma
  • Odontogenic sarcomas

Adenomatoid Odontogenic Tumor (AOT)

• AOT is a benign epithelial odontogenic tumor
• Types of AOT:
  • Follicular type: well-defined unilocular radiolucency involves the crown of an unerupted tooth
  • Extrafollicular type: well-defined unilocular radiolucency usually located between the roots of erupted teeth
  • Peripheral type: rare, situated in gingiva
• Histopathological features:
  • The tumor may be solid or cystic
  • Made of spindle-shaped epithelial cells that form sheets, islands, and whorled masses of cells in a little fibrous connective tissue stroma
  • Rings of columnar epithelial cells give rise to tubular structure, convoluted bands, and duct-like structures
  • Ghost cells are present and may undergo calcification

Odontoma

• Definition: a non-neoplastic developmental malformation (hamartoma) that contains fully formed enamel, dentine, cementum, and pulp
• Etiology:
  • Unknown origin
  • Local trauma or infection
  • Genetic (inherited or mutation)
• Types of odontomas:
  • Compound odontoma: a malformation in which all dental tissues are represented in a more orderly pattern than in the complex odontoma
  • Complex odontoma: a malformation in which all dental tissues are represented in a more disorderly pattern than in the compound odontoma

Cementoblastoma (True Cementoma)

• Definition: a rare benign ectomesenchymal odontogenic tumor of cementoblast origin, related to a vital tooth
• Origin: periodontal ligament and cementoblast
• Clinical features:
  • Age incidence: average age is 25 years
  • Sex incidence: male > female
  • Site predilection: mandible > maxilla (especially lower first permanent molar)
  • Symptom and signs: o It forms an irregular or rounded mass attached to the apical ⅓ of the roots o Slow growing with bony expansion o Pain is diagnostic feature, usually of low-grade intermittent pain and becomes more intense when the area is palpated o The associated tooth is vital
• Radiographic features:
  • Typically appears as a well-demarcated radiopaque mass with a thin radiolucent rim attached to the root of the lower tooth
  • Resorption of the related root is common
• Histopathological features:
  • It consists of sheets and thick trabeculae of mineralized material (cementum or cementum-like tissue) with prominent basophilic reversal lines and cells lying in lacunae

Odontogenic Tumors

• Odontogenic tumors are a group of neoplasms and tumors-like malformations derived from epithelial and/or ectomesenchymal elements that are part of the tooth-forming apparatus.

Classification of Odontogenic Tumors (WHO, 2005)

• Benign odontogenic tumors:
• Odontogenic epithelium with mature, fibrous stroma without odontogenic ectomesenchyme:
  • Ameloblastoma (solid/multicystic, extraosseous/peripheral, desmoplastic, and unicystic types)
  • Squamous odontogenic tumor
  • Calcifying epithelial odontogenic tumor
  • Adenomatoid odontogenic tumor
  • Keratinizing cystic odontogenic tumor
• Odontogenic epithelium with odontogenic ectomesenchyme, with or without hard tissue formation:
  • Ameloblastic fibroma
  • Ameloblastic fibro-odontoma
  • Ameloblastic fibro-dentinoma
  • Odontoma (complex and compound types)
  • Odontoameloblastoma
  • Calcifying cystic odontogenic tumor
  • Dentinogenic ghost cell tumor

Adenomatoid Odontogenic Tumor

• Well-encapsulated tumor with fibrous CT capsule
• Lobules of polyhedral-shaped epithelial cells
• Sheets of spindle-shaped epithelial cells
• Duct-like structure of columnar epithelial cells with eosinophilic band
• Convoluted tubules of columnar epithelial cells
• Areas of calcification
• Treatment: simple enucleation
• Prognosis: good prognosis (benign tumor with no recurrence rate due to encapsulation)

Calcifying Epithelial Odontogenic Tumor (CEOT/Pindborg's Tumor)

• Definition: benign, locally invasive epithelial neoplasm characterized by development of intra-epithelial amyloid-like material that may become calcified and liberated into surrounding stroma
• Origin: stratum intermedium of the enamel organ or reduced enamel epithelium, dental lamina, and its remnants (epithelial rests of Serres)
• Clinical features: average age incidence of 40 years, no sex predilection, and central (intra-osseous) mandible > maxilla
• Treatment: not mentioned

Ameloblastic Fibroma

• Definition: rare, benign mixed odontogenic tumor in which both epithelial and ectomesenchymal tissues are neoplastic
• Origin: dental papilla, dental follicle, or periodontal ligament
• Clinical features: average age incidence in the 1st and 2nd decades, male > female, mandibular premolar-molar area, painless, slowly growing swelling
• Radiographic features: well-defined unilocular (mainly) or multilocular radiolucent area, may be surrounded by sclerotic border, and often associated with unerupted tooth
• Histopathological features:
• Well-circumscribed, may or may not be encapsulated
• Highly cellular mesenchymal tissue resembling primitive dental papilla, mixed with proliferated odontogenic epithelium
• Epithelial components: show one of two patterns
  • Long anastomosing cords, strands, usually only two cells in thickness, composed of cuboidal or columnar cells
  • Small discrete islands resembling enamel organ (peripheral columnar cells with reverse polarity resembling ameloblasts surround a central mass of loosely arranged star-shaped cells resembling stellate reticulum)
• Mesenchymal components: plump stellate and ovoid cells in a loose matrix resemble immature dental papilla with little collagen fibers
• Juxta-epithelial hyalinization (cell-free zone) around epithelial islands

Odontoma

• Definition: non-neoplastic developmental malformation (hamartoma) that contains fully formed enamel, dentine, cementum, and pulp
• Etiology: unknown origin, local trauma or infection, and genetic (inherited or mutation)
• Both epithelial and mesenchymal cells exhibit complete differentiation, resulting in the formation of functional ameloblasts and odontoblasts that form enamel and dentine
• Types of odontomas:
• Compound odontoma: malformation in which all dental tissues are represented in a more orderly pattern than in the complex odontoma, composed of multiple small tooth-like structures
• Complex odontoma: malformation in which all dental tissues are represented in a more disorderly pattern than in the compound odontoma

Cementoblastoma (True Cementoma)

• Definition: rare, benign ectomesenchymal odontogenic tumor of cementoblast origin, related to a vital tooth
• Origin: periodontal ligament and cementoblast
• Clinical features: average age incidence of 25 years, male > female, mandible > maxilla (especially lower first permanent molar), slow-growing with bony expansion, and pain is a diagnostic feature
• Radiographic features: well-demarcated radiopaque mass with a thin radiolucent rim attached to the root of the lower tooth, resorption of the related root is common
• Histopathological features:
• Sheets and thick trabeculae of mineralized material (cementum or cementum-like tissue) with prominent basophilic reversal lines and cells lying in lacunae
• Mineralized trabeculae lined by prominent cementoblast cells
• Cellular fibrovascular tissue between mineralized trabeculae
• Periphery composed of uncalcified matrix
• Multinucleated cementoclasts seen
• Treatment: excision with extraction of the associated tooth
• Prognosis: good prognosis, no recurrence

Odontogenic Tumors

• Definition: A group of neoplasms and tumors-like malformations (hamartomas) derived from epithelial and/or ectomesenchymal elements that are parts of the tooth forming-apparatus.
• Origin: Odontogenic tissues.

Classification of Odontogenic Tumors (WHO, 2005)

• Benign Odontogenic Tumors:
  • Odontogenic epithelium with mature, fibrous stroma without odontogenic ectomesenchyme:
    • Ameloblastoma (solid/multicystic, extraosseous/peripheral, desmoplastic, unicystic types)
    • Squamous odontogenic tumor
    • Calcifying epithelial odontogenic tumor
    • Adenomatoid odontogenic tumor
    • Keratinizing cystic odontogenic tumor
  • Odontogenic epithelium with odontogenic ectomesenchyme, with or without hard tissue formation:
    • Ameloblastic fibroma
    • Ameloblastic fibro-odontoma
    • Ameloblastic fibro-dentinoma
    • Odontoma (complex, compound types)
    • Odontoameloblastoma
    • Calcifying cystic odontogenic tumor
    • Dentinogenic ghost cell tumor
  • Granular Cell Ameloblastoma: characterized by changing stellate reticulum-like cells to granular cells with eosinophilic granules.

Ameloblastoma

• Subtypes:
  • Acanthomatous Ameloblastoma: stellate reticulum-like cells undergo squamous metaplasia, producing keratin in form of keratin pearls.
  • Basaloid Ameloblastoma: stellate reticulum-like cells change to nests of hyperchromatic basaloid cells.
  • Desmoplastic Ameloblastoma: showing compressed follicles due to deposition of large amount of collagen fibers in the stroma.
• Treatment: The conventional ameloblastoma tends to infiltrate between intact cancellous bone trabeculae at the periphery of the tumor, requiring marginal resection at least 1cm past the margins to reduce the recurrence rate.

Unicystic Ameloblastoma

• Definition: A locally invasive tumor consisting of a central large cystic cavity, less aggressive than conventional ameloblastoma.
• Origin: De-novo as a neoplasm or neoplastic transformation of a pre-existing odontogenic cyst (dentigerous cyst).
• Clinical Features:
  • Age incidence: common in younger patients (average age 23 years).
  • Sex incidence: male = female.
  • Site predilection: mandible > maxilla, 90% occurs in lower posterior area with unerupted lower wisdoms.
  • Symptoms & signs: asymptomatic, large lesions may cause painless, slowly growing swelling, associated with impacted 3rd molar.
• Radiographic Features: Appears as a well-defined unilocular radiolucency that surrounds the crown of the unerupted third molar, resembling a dentigerous cyst.
• Histopathological Features:
  • Three histopathological variants:
    • Luminal Ameloblastoma: tumor tissue is confined to the luminal surface of the cyst.
    • Intra-luminal Ameloblastoma: one or more nodules of ameloblastoma project from the cystic lining into the lumen of the cyst.
    • Mural Ameloblastoma: the fibrous wall of the cyst is infiltrated by follicular or plexiform ameloblastoma.
• Treatment: usually treated as cysts by enucleation (without safety margin) with recurrence rate 10-20%. Mural variant should be treated aggressively like conventional ameloblastomas.

Adenomatoid Odontogenic Tumor (AOT)

• Definition: A benign tumor consisting of spindle-shaped epithelial cells that form sheets, islands, and whorled masses of cells in a little fibrous C.T. stroma.
• Clinical Features:
  • Age incidence: 40 years.
  • Sex incidence: female > male.
  • Site predilection: commonly in anterior maxilla.
  • Symptoms & signs: small lesions usually asymptomatic, larger lesions associated with localized bony expansion or loosening of adjacent teeth.
• Radiographic Features: Appears as a well-defined unilocular radiolucency, often with faint (snowflakes) calcifications or patchy radiopacities.
• Histopathological Features:
  • Tumor composed of:
    • Spindle-shaped epithelial cells forming sheets, islands, and whorled masses.
    • Rings of columnar epithelial cells giving rise to tubular, convoluted bands, and duct-like structures.
  • Eosinophilic material is thought to be a basement membrane-like material, PAS positive.

Odontogenic Fibroma

• Definition: A benign, fibroblastic neoplasm containing varying amounts of inactive odontogenic epithelium.
• Origin: Periodontal ligament, dental papilla, or dental follicles.
• Clinical Features:
  • Age incidence: 40 years.
  • Sex incidence: female > male.
  • Site predilection: commonly in anterior maxilla.
  • Symptoms & signs: small lesions usually asymptomatic, larger lesions associated with localized bony expansion or loosening of adjacent teeth.
• Radiographic Features: Appears as a well-defined unilocular radiolucency.
• Histopathological Features:
  • Composed of:
    • Cellular fibrous tissue containing strands and islands of inactive odontogenic epithelium.
    • Calcifications composed of osteoid or cement-like tissues and dysplastic dentine may be present.
  • Stellate fibroblasts and immature collagen resembling dental papilla.
• Treatment: Enucleation & curettage.
• Histological variants: Simple (epithelial-poor type) and WHO (epithelial-rich type)