Mandible-Maxilla
Benign tumors
Ameloblastoma - unicystic variant

Authors: Kelly Magliocca, D.D.S., M.P.H. and Anthony Martinez, M.D. (see Authors page)

Revised: 21 July 2016, last major update June 2016

Copyright: (c) 2002-2016, PathologyOutlines.com, Inc.

PubMed Search: Unicystic variant

Cite this page: Ameloblastoma - unicystic variant. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/mandiblemaxillaunicystic.html. Accessed June 26th, 2017.
Definition / general
  • 20% of all ameloblastomas
  • Mean age 25 years (younger than classic type), range 8 - 60 years, 2/3 male
  • > 90% in mandible, 63% at angle and ascending ramus
  • Recurrence related to fibrous wall invasion: 36% recur with vs. 7% without; recurrence may be long delayed
  • May be associated with nevoid basal cell carcinoma (Gorlin) syndrome (Fam Cancer 2012;11:411)
Radiology description
  • Expansile lesion, often unicystic or unilocular radiographically
    • Variable association with impacted tooth
    • Often displaces teeth, but may also resorb teeth
Radiology images

Images hosted on other servers:

Cystic tumor penetrating cortex

Case reports
Treatment
  • Treatment of luminal and intraluminal variants is controversial, and dependent on the radiographic presentation and confidence that mural unicystic ameloblastoma has been excluded
Gross description
  • Cystic sac or fragments of cyst wall, up to several centimeters in size
  • Often requires the specimen be entirely submitted in order to exclude mural ameloblastoma
Microscopic (histologic) description
  • Single cystic lesion lined by ameloblastic epithelium that shows typical features of ameloblastoma in some areas, including columnar basal cells in palisading arrangement with vacuolated cytoplasm, hyperchromatic nuclei polarized away from basement membrane
  • Suprabasal cells loosely textured and noncohesive resembling stellate reticulum, epithelial invagination, epithelial edema and separation
  • May have intraluminal plexiform patterns
  • Tumor islands may invade fibrous capsule with subepithelial hyalinization

  • Microscopic variants (may result in treatment differences – controversial)
    • Luminal: cystic odontgenic epithelium with characteristic features (above) lining fibrous connective tissue wall
    • Intraluminal: cystic odontgenic epithelium with characteristic features (above) lining fibrous connective tissue wall, with tumor extending into the cystic luminal space
    • Mural: cystic odontgenic epithelium with characteristic features (above) lining fibrous connective tissue wall but with the additional finding of definite ameloblastoma tumor islands within the fibrous connective tissue wall
Microscopic (histologic) images

Images hosted on other servers:

Edematous epithelium with basal cell palisading

Unicystic ameloblastoma (figure 3)

Differential diagnosis
  • Calcifying cystic odontogenic tumor
    • Benign cystic tumor of odontogenic origin aka “Gorlin cyst” or “Calcifying odontogenic cyst”
    • Can have “ameloblastic” features: columnar or cuboidal basal cells with lumen lined by tissue resembling stellate reticulum
    • Will have ghost cells or anucleate epithelial cells

  • Keratocystic odontogenic tumor
    • Benign cystic tumor of odontogenic origin aka “Odontogenic Keratocyst”
    • Can have prominent and hyperchromatic basal layer, typically palisading is present
    • Absent is stellate reticulum-like layer

  • Dentigerous cyst
    • Benign odontogenic cyst with limited potential for recurrence
    • Radiographically must be situated around an impacted tooth
    • Can have basal palisading and focally an appearance of stellate-reticulum-like material
    • In limited sample, may not be distinguishable from unicystic ameloblastoma

  • Macrocystic degeneration of conventional ameloblastoma (limited biopsy sample requires inclusion of this entity in differential diagnosis)
    • Basal palisading, with reverse polarity, hyperchromatic basal layer
    • Stellate reticulum-like layer
    • Larger sample can be helpful in distinguishing type