Ameloblastoma pathophysiology

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Shivali Marketkar, M.B.B.S. [2]

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Overview

On gross pathology, the characteristic findings of ameloblastoma may include solid and cystic, mulitcystic 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.

Pathophysiology

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.
• Shown below is the gross specimen of resected left half of mandible initiated at third molar.

Microscopic Pathology

• 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 vacuolization.
• 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)

Shown below is a micrograph of ameloblastoma

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 vacuolization 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

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