Oral Pathology: Odontogenic Tumors

Oral Pathology

• Oral pathology is the study of diseases affecting the oral cavity.

Odontogenic Tumors

• Definition: Tumors arising from tooth-forming tissues (odontogenic tissues) and their remnants.
• Location: Primarily in the mandible and maxilla; occasionally the gingiva.
• Types: Some are true neoplasms; others are tumor-like malformations (hamartomas).
• Etiology/Pathogenesis: Unknown.

Origin of Odontogenic Tumors

• Ectodermal (Epithelial):
  • Dental lamina (and its remnants)
  • Epithelial rests of Serres
  • Enamel organ (reduced enamel epithelium)
  • Epithelial root sheath of Hertwig's
  • Epithelial rests of Malassez
• Mesenchymal (Connective Tissue):
  • Dental papilla
  • Dental sac (follicle)

Odontogenic Tissue

• Ameloblasts: Form enamel.
• Enamel: Outer layer of the tooth.
• Dentin: The main component of the tooth.
• Odontoblasts: Form dentin.
• Hertwig's sheath: Surrounds the developing root of the tooth.
• Pulp (papilla): Soft tissue inside the root.

Classification of Odontogenic Tumors

• Benign Epithelial:
  • Ameloblastoma
  • Adenomatoid odontogenic tumor
  • Adenoid ameloblastoma
  • Metastasizing ameloblastoma
  • Calcifying epithelial odontogenic tumor
  • Squamous odontogenic tumor
• Benign Mesenchymal:
  • Odontogenic myxoma
  • Odontogenic fibroma
  • Cementoblastoma
  • Cemento-ossifying fibroma
• Benign Mixed:
  • Odontoma
  • Primordial odontogenic tumor
  • Ameloblastic Fibroma
  • Dentinogenic ghost cell tumor
• Malignant:
  • Ameloblastic carcinoma
  • Sclerosing odontogenic carcinoma
  • Clear cell odontogenic carcinoma
  • Ghost cell odontogenic carcinoma
  • Odontogenic carcinosarcoma
  • Odontogenic sarcomas

General Features of Odontogenic Tumors

• Clinical Features: Clinically, odontogenic tumors are often asymptomatic, but may cause jaw expansion, tooth movement, root resorption, and bone loss.
• Histological Features: Microscopically, odontogenic tumors often mimic the cells or tissues from which they originate.
• Tissue Resemblance: They may resemble soft tissues (like the enamel organ or dental pulp) or contain hard tissues (enamel, dentin, or cementum).

Epithelial Odontogenic Tumors

• Ameloblastoma (1):

  • Definition: Benign, locally aggressive epithelial odontogenic neoplasm; slow-growing.
  • Common type.
  • Three types: conventional (intraosseous), unicystic (intraosseous), and peripheral(extraosseous).
    • Subtypes of conventional (like follicular and plexiform) and unicystic (luminal, intraluminal and mural).
  • Origin: Remnants of dental lamina, enamel organ, odontogenic cyst, basal cells of oral mucosa
  • Clinical features: Most common in 4th and 5th decades of life; 85% in mandible, mostly near ramus, 15% in maxilla. Slow growth, untreated may reach a large size.
  • Radiographic features: Generally multilocular radiolucent lesions (soap bubble, honeycomb appearance). May appear as unilocular defects associated with unerupted teeth, especially mandibular third molars.
  • Histopathologic features of follicular ameloblastoma: Epithelium form discrete islands, central cells resemble stellate reticulum of enamel organ, surrounding layer of tall columnar ameloblast-like cells.
  • Additional types (features): Cystic follicular: cyst-like, Acanthomatous ameloblastoma: keratin formation, Granular cell ameloblastoma: granular cells, Basaloid ameloblastoma: uniform basaloid cells, Desmoplastic ameloblastoma: densely collagenized stroma
  • Histologic feature of plexusform ameloblastoma consists of anastomosing cords of odontogenic epithelium with central stellate reticulum like cells, surrounded by connective tissue stroma. Cystic formation may occur by stromal breakdown. Stromal blood vessels may appear dilated.
  • Unicystic Ameloblastoma: origin from de novo or results of dentigerous. Clinical features are similar to ameloblastoma, the most case found in mandible in posterior regions. Radiographically unilocular radiolucency that may contain crown of an unerupted mandibular third molar. (Luminal, Intraluminal, Mural).
  • Peripheral Ameloblastoma originate in rests of dental lamina - beneath mucosa or from surface epithelium cell. Clinically painless swelling in posterior gingival and alveolar mucosa and is more common in mandible, clinically negative in X-ray.

• Adenomatoid odontogenic tumor:

  • Benign epithelial tumor.
    • Contains duct-like structures.
  • Origin: Enamel organ, or remnants of dental lamina.
  • Clinical features: Usually in the second decade, most lesions in maxilla anterior. Small tumor.
  • Radiographic features: Well-circumscribed unilocular radiolucency, may include unerupted tooth crown, fine calcifications
  • Histopathologic features: Tumor surrounded by thick fibrous capsule, composed of spindled epithelium. Forms rosettes. Containing eosinophilic material. Tubular ducts also a characteristic feature with a central space surrounded by epithelial (columnar/cuboidal) layer around.

• Calcifying Epithelial Odontogenic Tumor (Pindborg tumor):

  • Benign tumor.
  • Origin: Enamel organ or remnants of dental lamina.
  • Clinical features: Fourth decade; posterior mandible.
  • Radiographic features: Circumscribed unilocular/multilocular radiolucency. May contain radiopaque calcifications.
  • Histopathologic features: Discrete islands, strands, or sheets of polyhedral epithelial cells, varying nuclei size/shape, large areas of amorphous, eosinophilic, hyalinized extracellular material, calcifications form concentric rings (Liesegang rings).

• Adenoid Ameloblastoma:

  • New entity in odontogenic lesions. A hybrid benign tumor, showing combined histopathological features of ameloblastoma and adenomatoid odontogenic tumor.
  • Clinical features: 2nd-5th decade of life; more than two-thirds reported in mandible.
  • Radiographic features: Unilocular or multilocular radiolucency; may appear as mixed density due to dentinoid presence.
  • Histopathologic features: Cribriform architecture, duct-like structures, dentinoid frequently present. Clear cells, ghost-cell keratinization.

• Metastasizing Ameloblastoma:

  • An ameloblastoma that metastasized despite benign appearance.
  • Locations for metastasis: lungs and cervical lymph nodes; spread to vertebrae, other bones, and viscera also possible.
  • Radiographic features: Similar to non-metastasizing ameloblastoma.

• Squamous Odontogenic Tumor:

  • Rare benign neoplasm.
  • Origin: Dental lamina rests or epithelial rests of Malassez.
  • Clinical features: 8-74 years (avg age 38); no site preference; painless to mildly painful gingival swelling, often associated with tooth mobility.
  • Radiographic features: Triangular radiolucent lateral to tooth root/roots; radiolucency may be somewhat ill-defined or have a well-defined corticated margin. May cause tooth displacement/resorption.
  • Histopathologic features: Varying shaped islands of bland-appearing squamous epithelium; peripheral cells do not show reverse polarization characteristic of ameloblastoma. Vacuolization and individual cell keratinization, laminated calcified bodies and eosinophilic structures likely represent dystrophic calcification.

Mesenchymal Odontogenic Tumors

• Odontogenic Myxoma:

  • Locally destructive, benign mesenchymal tumor.
  • Origin: Odontogenic mesenchyme.
  • Clinical features: Young adults (25-30 years); mandible more common. Rapidly growing.
  • Radiographic features: Multilocular radiolucency (soap-bubble, honeycomb appearance).
  • Histopathologic Features: Tumor composed of stellate or spindled cells with abundant, myxoid (mucoid) stroma containing few collagen fibrils.

• Cementoblastoma (True cementoma):

  • Benign tumor of cementoblasts.
  • Origin: Dental sac.
  • Clinical features: Before 25 years of age; mandibular premolar/molar region; common; associated with the root of a vital tooth.
  • Radiographic features: Radiopaque mass fused to one or more tooth roots; thin radiolucent rim; root resorption and fusion with tooth common.
  • Histopathologic Features: Dense mineralized cementum with numerous basophilic reversal lines; uncalcified matrix in periphery.

• Cemento-ossifying Fibroma:

  • Fibro-osseous lesion with varied patterns of bone formation.
  • Origin: Cells of periodontal ligament.
  • Clinical features: Slow growth; may cause extensive jaw expansion; asymptomatic small lesions. Mostly mandibular premolar/molar region
  • Radiographic features: Mature lesion = radiopaque; early = radiolucent; well-defined corticated radiolucency/margin.
  • Histopathologic features: Variable proportion of fibrous and mineralized tissue heavily mineralized centrally; variation in mineralization even within single lesion; Woven to lamellar bone, osteoid and dense acellular or paucicellular basophilic rounded cementum-like calcifications; Osteoblastic rimming of bone trabeculae frequent. Stroma is fibroblastic with areas of hypercellularity and nuclear hyperchromasia; no significant atypia and mitoses infrequent. Hyperparathyroidism Jaw Tumor Syndrome (HPT-JT) predisposes to multiple C.O.F

Mixed Odontogenic Tumors

• Ameloblastic Fibroma:

  • Mixed benign odontogenic tumor (epithelial and mesenchymal tissues neoplastic).
  • Clinical features: First two decades; posterior mandible common.
  • Radiographic features: Well-defined unilocular/multilocular radiolucency; possible unerupted tooth.
  • Histopathologic features: Epithelial portion = long, narrow cords; peripheral columnar cells surrounding stellate-reticulum-like cells; mesenchymal component = highly cellular, stellate cells resembling dental papilla.

• Odontoma:

  • Mixed odontogenic tumor (epithelial and mesenchymal hard tissues develop). Considered developmental anomaly/hamartoma, not true neoplasm.
  • Clinical features: First two decades; maxilla slightly more common than mandible; compound = more anterior, complex = often molar regions.
  • Radiographic features: Compound = tiny tooth-like structures; complex = radiopaque mass with tooth-like radiodensity.
  • Histopathologic features: Compound = multiple small tooth-like structures with well-organized dental tissue (enamel matrix, dentin, pulp) in loose fibrous matrix. Complex = disordered mixture of dental tissues; dentin encloses clefts, possibly containing enamel matrix.

• Dentinogenic Ghost Cell Tumor:

  • Benign, locally aggressive odontogenic neoplasm, predominantly solid growth pattern with high recurrence rate.
  • Clinical features: Broad age range (11-79 years), peak 40-60 years; posterior maxilla and mandible; uncommon in gingiva/alveolar mucosa. Asymptomatic jaw swelling frequent.
  • Radiographic features: Predominantly radiopaque lesions with well-defined borders; mixed radiodensity due to varying calcification levels.
  • Histopathologic features: Predominantly solid mass of anastomosing cords/strands odontogenic epithelium; varying dentinoid and cementum-like calcified collagenous matrix possible. Ameloblastic like areas with palisading basaloid cells; odontogenic cells have uniform, basophilic nuclei and pale eosinophilic to clear cytoplasm. Ghost cells = anucleate epithelial cells with pale cytoplasm.

• Primordial Odontogenic Tumor:

  • Uncommon odontogenic tumor with biphasic morphology.
  • Clinical features: First and second decades of life; mandible more frequent than maxilla.
  • Radiographic features: Unilocular radiolucent lesion associated with the crown of an unerupted tooth.
  • Histopathologic features: Abundant collagenous/fibromyxoid stroma; exhibiting spindle/ovoid cells resembling dental papilla; odontogenic epithelium composed of cuboidal/columnar cells with clear cytoplasm; reversal nuclear polarity; resembles inner enamel epithelium in periphery of the tumor.

Malignant Odontogenic Tumors

• Ameloblastic Carcinoma:

  • Rare malignant ameloblastoma. Rapid growth; metastasis.
  • Radiographic features: Aggressive; poorly defined margin.
  • Histopathologic features: Ameloblastoma features plus cytologic malignant features (increased nuclear-to-cytoplasmic ratio, nuclear hyperchromatism, mitoses).

• Sclerosing Odontogenic Carcinoma:

  • Locally aggressive. Perineural and vascular invasion, cortical bone loss.
  • Radiographic features: Not specific.
  • Histopathologic features: Thin cords/strands/small epithelial nests in densely sclerotic stroma. High stroma density may obscure epithelium. Nuclear pleomorphism is present.

• Clear Cell Odontogenic Carcinoma:

  • Wide age range (20-86 years); female predilection; mandibular involvement prevalent. Slow growth; painful jaw swelling with poorly defined radiographic appearance.
  • Radiographic features: Not specific.
  • Histopathologic features: Predominant clear cells histologically; three possible morphological patterns: biphasic, consisting of nests of clear cells with cells having faint eosinophilic cytoplasm. Monophasic, composed only of clear cells. Ameloblastomatous exhibiting ameloblast-like cells in the periphery of tumor cell islands.

• Ghost Cell Odontogenic Carcinoma:

  • Extremely rare, destructive, aggressive malignant tumor; can originate de novo, or from pre-existing calcifying odontogenic cyst or dentinogenic ghost cell tumor.
  • Clinical features: 4th-5th decades; higher occurrence in males; maxilla.
  • Histopathologic features: Ghost cells prominent in epithelial islands; ameloblastoma-like epithelium is evident with ghost cells; cytologic malignancy presence; dentinoid formation.

• Primary Intraosseous Carcinoma-NOS:

  • Difficult differentiation from carcinomas invading bone from overlying tissues or from metastasized tumors; may arise from reduced enamel epithelium, or odontogenic cysts.
  • Clinical features: 55-60 years; male predominant; common in posterior mandible; painless or painful jaw swelling with intact overlying mucosa.
  • Radiographic features: Destructive jaw lesions.
  • Histopathologic features: Squamous carcinomas with well to moderate differentiation, with or without inflammatory infiltrate. Diagnosis of exclusion; exclude other mimickers (malignant odontogenic subtypes, metastatic lesions).

• Odontogenic Carcinosarcoma:

  • Associated with both mesenchymal and epithelial malignant cells.
  • EX= ameloblastic carcinosarcoma.
  • Results from transformation from the epithelial and mesenchymal components of ameloblastic fibroma.

• Odontogenic Sarcoma:

  • Appear in third decade; associated with bland-looking epithelial and malignant mesenchymal cells.
  • Includes ameloblastic fibrosarcoma, ameloblastic dentinosarcomas, and ameloblastic fibroodontosarcomas.