Ameloblastoma pathophysiology

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Shivali Marketkar, M.B.B.S. [2], Vamsikrishna Gunnam M.B.B.S [3]

Ameloblastoma Microchapters
Home
Overview
Historical Perspective
Classification
Pathophysiology
Causes
Differentiating Ameloblastoma from other Diseases
Epidemiology and Demographics
Risk Factors
Screening
Natural History, Complications and Prognosis
Diagnosis
Diagnostic Study of Choice
History and Symptoms
Physical Examination
Laboratory Findings
Electrocardiogram
X-Ray
CT
MRI
Echocardiography and Ultrasound
Other Imaging Findings
Other Diagnostic Studies
Treatment
Medical Therapy
Surgery
Primary Prevention
Secondary Prevention
Cost-Effectiveness of Therapy
Future or Investigational Therapies
Case Studies
Case #1
Ameloblastoma pathophysiology On the Web
Most recent articles
Most cited articles
Review articles
CME Programs
Powerpoint slides
Images
American Roentgen Ray Society Images of Ameloblastoma pathophysiology All Images X-rays Echo & Ultrasound CT Images MRI
Ongoing Trials at Clinical Trials.gov
US National Guidelines Clearinghouse
NICE Guidance
FDA on Ameloblastoma pathophysiology
CDC on Ameloblastoma pathophysiology
Ameloblastoma pathophysiology in the news
Blogs on Ameloblastoma pathophysiology
Directions to Hospitals Treating Ameloblastoma
Risk calculators and risk factors for Ameloblastoma pathophysiology

Overview

Ameloblastoma arise from remnants of ameloblast or dental lamina, dentigerous cysts, or basal layer of oral mucosa. There is evidence that suppression of matrix metalloproteinase-2 may inhibit the local invasiveness of ameloblastoma. On gross pathology, the characteristic findings of ameloblastoma may include solid and cystic, multicystic and intraosseous or extraosseous, or rarely unicystic. On microscopic histopathological analysis, stellate reticulum, giant cells, subepithelial hyalinization, and columnar basal cells in palisading arrangement with vacuolated cytoplasm are characteristic findings of ameloblastoma. The exact pathophysiology of ameloblastoma is not fully understood. It is thought that ameloblastoma is the result of either suppression of matrix metalloproteinase-2 that may inhibit the local invasiveness of ameloblastoma, or there is also some research suggesting that α5β1 integrin may participate in the local invasiveness of ameloblastoma. Genes involved in the pathogenesis of ameloblastoma include BRAF V600E.

Pathophysiology

Pathogenesis

• Ameloblastoma arise from remnants of ameloblast or dental lamina, dentigerous cysts, or basal layer of oral mucosa.
• Ameloblasts, which are part of the odontogenic epithelium, are responsible for enamel production and eventual crown formation.
• There is evidence that suppression of matrix metalloproteinase-2 may inhibit the local invasiveness of ameloblastoma, however, this was only demonstrated in vitro.
• There is also some research suggesting that α5β1 integrin may participate in the local invasiveness of ameloblastomas.
• The ameloblastoma is an ectodermal odontogenic tumor of the jaw which apparently originates from the Malassez rests in the periodontium, from the gingival epithelium, from the enamel organs, or from ordinary dental cysts (dentigerous cysts, follicular cysts, or radicular cysts).

Genetics

Genes involved in the pathogenesis of ameloblastoma include:

• BRAF V600E

Gross Pathology

On gross pathology the following are the characteristic findings of ameloblastoma:

• Solid and cystic
• Multicystic and intraosseous or extraosseous
• Rarely may be unicystic

Microscopic Pathology

On microscopic examination, the following characteristic findings of ameloblastoma are present:

• Stellate reticulum - star-shaped cells, found in a developing tooth
• Giant cells may or may not be present
• Subepithelial hyalinization may or may not be present
• Seen deep to the basement membrane
• Suprabasal cells loosely textured and noncohesive, resembling stellate reticulum
• The plexiform type has epithelium that proliferates in a "Fish Net Pattern"
• The follicular type will have outer arrangement of columnar or palisaded ameloblast like cells and inner zone of triangular shaped cells resembling stellate reticulum in bell stage. The central cells sometimes degenerate to form central microcysts
• No enamel or dentin formation
• 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 perpendicular to the basement membrane (key feature)
  • Subnuclear vacuolation
• The following are the different histopathological variants of ameloblastoma:
  • Intraosseous (follicular, plexiform, acanthomatous, multicystic, unicystic, granular cell [lysosomes by EM], basal cell, desmoplastic)
  • Extraosseous (follicular, plexiform, basal cell)

The image shows the characteristic features:

• Islands of cells with palisaded nuclei that have 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 perpendicular to the basement membrane

• Subnuclear vacuolation in palisading cell - vacuoles at the basement membrane aspect
• Loose stroma around the islands of cells
• Star-like cells at the centre of the islands of cells (stellate reticulum)

Video

{{#ev:youtube|VW5aSalmyF0}}