Odontogenic tumours and cysts

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This article covers odontogenic tumours and cysts, which is a subset of oral pathology and can be grouped under the heading of head and neck pathology.

The general topic of head and neck pathology is covered in the head and neck pathology and head and neck cytopathology articles.

Tooth histiology 101

Teeth develop from a combination of:

  1. Epithelium (downward growth).
  2. Mesenchyme.

Identifying stuff

Pulp:

  • Paucicellular.
  • Pale staining.

Enamel:

  • Hyperchromatic (dark purple).
  • "Fish scale" appearance.

Enamel 101

  • Arises from reduced enamel epithelium.

Reduced enamel epithelium

Microscopic

Features:

  • Bilayered epithelium consisting of:
    • Cuboidal/columnar cells with:
      • Moderate eosinophilic cytoplasm.
      • Round (slightly irregular) centrally place nuclei.

Notes:

  • Transforms into squamous epithelium. (???)

Compound odontome

General

  • Usually diagnosed clinically.
  • Benign.

Microscopic

Features:

  • ???

Radicular cyst

  • AKA periapical cyst.

Clinical

  • Non-vital tooth - key feature.
    • The tooth that has lost its nerve.

Microscopic

Features:

  • Squamous epithelium - always non-keratinized.
  • +/-Giant cells.
  • +/-Cholesterol clefts.

DDx:

  • Dentigerous cyst (history is the key to differentiate).

Notes:

  • Keratinized epithelium: think keratocytic odontogenic tumour.

Dentigerous cyst

Clinical

  • Unerupted tooth - usually wisdom teeth.
    • Young adults.

Gross

  • Lesion at crown of tooth.

Microscopic

Features:

  • Squamous epithelium - always non-keratinized.
  • +/-Giant cells.
  • +/-Cholesterol clefts.

DDx:

  • Radicular cyst (history is the key to differentiate).

Notes:

  • Keratinized epithelium: think keratocytic odontogenic tumour.

Keratocystic odontogenic tumour

General

Clinical

Features:[2]

  • Most common presentation: swelling.
  • Location: usually mandible.
  • May mimic ameloblastoma radiologically.

Microscopic

Features: [3]

  • Stratified epithelium resembling squamous epithelium - typically 8-10 cell layers thick - with relatively uniform thickness ("ribbon-like appearance").
  • Artefactual separation of epithelium from the basement membrane.
  • Parakeratosis (keratinized cells with nuclei) -- key feature.
  • Palisaded basal cell layer.
  • Lacks rete ridges.

DDx:

  • Odontogenic cyst.
    • Orthokeratinized odontogenic cyst (has orthokeratosis instead of parakeratosis).
      • Orthokeratosis = keratinized cells no nuclei; parakeratosis = keratinized cell with nuclei.

Images:

Ameloblastoma

General

  • Osteous lesion.

Classification

Location:

  1. Intra-osseous.
    • Locally aggressive.
  2. Peripheral.
    • Benign.

Subclassification of intra-osseous type

Histology:

  1. Solid/multicystic.
    • More commonly reoccur.
  2. Unicystic.
    • Unlikely to reoccur.
    • Classically found in younger individuals.

Microscopic

Features:[4]

  • Stellate reticulum - star-shaped cells, found in a developing tooth.[5]
  • Tall columnar cells.
    • Palisaded nuclei with reverse polarization.
      • Reverse polarization of nuclei = nuclei distant from the basement membrane/nuclei at pole opposite of basement membrane.
      • Palisaded nuclei = picket fence appearance; columnar-shaped nuclei with long axis aligned perpendicular to the basement membrane -- key feature.
    • Subnuclear vacuolization.
  • +/-Giant cells.
  • +/-Subepithelial hyalinization (eosinophilic acellular amorphous material).
    • Seen deep to the basement membrane.
  • Variable morphology (see below - morphology).

DDx (nuclear palisading):

  • Adenomatoid odontogenic tumour.
  • Ameloblastic fibroma.

Images:

=Morphology

  • Not prognostic.

Morphologic variants:

  • Follicular ameloblastoma (classic appearance).
  • Plexiform ameloblastoma (does not have prominent pallisading).
  • Acanthomatous ameloblastoma.
  • Desmoplastic ameloblastoma.
  • Basaloid ameloblastoma.

Adenomatoid odontogenic tumour

General

  • Paedatric population.

Microscopic

Features:

  • Palisaded nuclei.
  • Whorled epithelium.

Notes:

  • No stellate reticulum.

DDx: Ameloblastoma.

Ameloblastic fibroma

General

  • Paedatric population.

Microscopic

Features:

  • Palisaded nuclei.
  • Fibrous stroma.

Notes:

  • No stellate reticulum.

DDx: Ameloblastoma.

Odontogenic myxoma

General

  • Benign tumour of mesenchymal origin.
  • Often reoccurs.
  • Radiologic DDx includes ameloblastoma.

Gross

  • Gelatinous mass.

Microscopic

Features:

  • Paucicellular lesion with pale staining.

See also

References

  1. ↑ Madras, J.; Lapointe, H. (Mar 2008). "Keratocystic odontogenic tumour: reclassification of the odontogenic keratocyst from cyst to tumour.". J Can Dent Assoc 74 (2): 165-165h. PMID 18353202.
  2. ↑ Habibi, A.; Saghravanian, N.; Habibi, M.; Mellati, E.; Habibi, M. (Sep 2007). "Keratocystic odontogenic tumor: a 10-year retrospective study of 83 cases in an Iranian population.". J Oral Sci 49 (3): 229-35. PMID 17928730.
  3. ↑ Thompson LDR. Head and neck pathology - (Foundations in diagnostic pathology). Goldblum JR, Ed.. Churchill Livingstone. 2006. ISBN 0-443-06960-3.
  4. ↑ URL: http://www.pathconsultddx.com/pathCon/diagnosis?pii=S1559-8675%2806%2970616-7. Accessed on: March 9, 2010.
  5. ↑ URL: http://en.wikipedia.org/wiki/Stellate_reticulum. Accessed on: March 9, 2010.
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