REMEMBER TWO TERMS

Pathogenesis

• The stimulus initiating the process is unknow.
• Although most authorities believe it can be derived from:
  1. 1. Remnants Of Enamel Organ – Remnants Of Dental Lamina or Remnants of Hertwig’s epithelial root sheath (epithelial rests of Malassez)
  2. 2. Epithelium of odontogenic cysts (particularly Dentigerous cyst) & Odontoma
  3. 3. Disturbances of enamel organ
  4. 4. Basal cells of surface epithelium of jaws
  5. 5. Heterotopic epithelium in other parts of the body especially pituitary gland
• Presently thought to be most likely result of alteration/mutation in genetic material of cells that are embryologically pre-programmed for tooth development

Based On Clinical & Radiographic Features It Is Classified As

• Conventional solid or multicystic (about 75% to 86% of all cases)
• Unicystic (about 13% to 21% of all cases)
• Peripheral (extraosseous) (about 1% to 4% of all cases)

Radiographic Features

• Classically – Multilocular cyst-like lesion of jaw. Compartmental appearance with septa of bone extending into radiolucent tumor mass (honeycomb or soap bubble appearance)
• Sometimes unilocular
• Periphery smooth
• In advanced lesion – jaw expansion – thinning of cortical plate

Ameloblastoma Basics Video Lecture – https://youtu.be/fJYesDgxQSQ

Histopathology Ameloblastoma – 6 Patterns:-

• Follicular (most common)
• Plexiform (2nd most common)
• Acanthomatous
• Granular cell
• Basal cell
• Desmoplastic

FAMOUS PEOPLE ARE GREAT BELLY DANCERS:-

• FAMOUS - Follicular (most common)
• PEOPLE - Plexiform (2nd most common)
• ARE - Acanthomatous
• GREAT - Granular cell
• BELLY - Basal cell
• DANCERS - Desmoplastic

Tumor has two components :-

• Epithelial component - disconnected islands, strands & cords in stroma
• Stromal Component – Moderately to densely collagenized

Let’s Now See The 6 Histopathologic Patterns/subtypes: –

• Most tumours show more than one type of histopathologic patterns. Lesions are subclassified based on predominant pattern present. According to a study by Reichart et al 1995, these histologic subtypes may have prognostic implications for recurrence.

1. Follicular Ameloblastoma –

• Most common & recognizable subtype
• Epithelial component in the form of small discrete tumor islands present in stromal tissue.
• These epithelial tumor islands will show 2 parts: –
  • 1. CENTRAL MASS OF CELLS – STELLATE RETICULUM LIKE CELLS (angular to polyhedral in shape)
  • 2. PERIPHERAL LAYER OF CELLS – AMELOBLAST LIKE CELLS
• These peripheral layer of cells (ameloblast like cells) under high magnification show certain characteristics described by Vickers & Gorlin
• These peripheral layer of cells (ameloblast like cells) under high magnification show certain characteristics described by Vickers & Gorlin
• Vickers & Gorlin Criteria (1970) (Important)
  • 1. Tall columnar cell
  • 2. Hyperchromatic nucleus (stain more intensely than normal)
  • 3. Palisaded nuclei
  • 4. Reverse polarity of the nuclei (nuclei of the cells located at the opposite pole to the basement membrane)
  • 5. Sub-nuclear vacuole formation
• Sometimes cystic degeneration seen within epithelial islands of follicular ameloblastoma.

Follicular Ameloblastoma (Low Magnification)

Follicular Ameloblastoma High Magnification

2. Plexiform Meloblastoma –

• 2nd most common
• Word plexiform means network or plexus
• Thus, plexiform ameloblastoma shows epithelial component in form of a network or plexus; there is a network of inter anastomosing strands. Each of these strands is bounded by:-
  • Peripheral layer of cells are cuboidal to columnar, and will not strictly follow Vickers & Gorlin Criteria.
  • Central mass of cells are stellate reticulum-like (angular to polyhedral in shape). These stellate reticulum-like cells are not as prominent as seen in follicular type.
• Areas of cystic degeneration may be seen in stroma and not within epithelial component.

3. Acanthomatous Ameloblastoma –

• Squamous metaplasia, often associated with keratin formation, occurs in the central portions of the epithelial islands of a follicular ameloblastoma, the term Acanthomatous ameloblastoma is used.

4. Granular Cell Ameloblastoma –

• In this type, cytoplasm becomes coarse granular eosinophilic appearance (usually of stellate reticulum-like cells, often extends to include peripheral cuboidal or columnar cells)
• Granules represent lysosomal aggregates ultra-structurally

5. Basal Cell Ameloblastoma –

• Resembles basal cell carcinoma of skin
• Rarest type
• Least common
• Epithelial tumour cells are more primitive, less columnar, arranged in sheets

6. Desmoplastic Ameloblastoma –

• Dense collagenous stroma
• Thin cords of epithelium
• Epithelium compressed & fragmented by dense stroma
• Central cells scant
• Peripheral cells are flattened or cuboidal rather than tall columnar
• Most desmoplastic ameloblastomas display occasional classic islands of follicular ameloblastoma among the predominant strands and cords. Without these classic islands of ameloblastoma, the diagnosis can be difficult.

Treatment & Prognosis –

• Complete surgical removal & Long term follow up due to high recurrence rate
• Most preferred Surgical excision (radical over conventional)
• The growth pattern of the neoplasm, categorized as conventional or unicystic, is more important than the histopathologic subtype in treatment decision

References –

• Shafer’s Textbook Of Oral Pathology
• Neville – Oral & Maxillofacial Pathology
• Image – Wikipedia & Wikimedia Commons