• Most common odontogenic tumor
• Benign
• Locally invasive

Clinicopathological subtypes

1. Solid/multicystic
2. Unicystic
3. Desmoplastic
4. Peripheral/extraosseous

Etiology

• Unknown – Trauma, inflammation, infection

Epidemiology

• 4th-5th decade
• M = F

Site

• Mandible : Maxilla = 4 : 1
• Mandible sites:
  • 70% molar ramus area
  • 20% premolar region
  • 10% incisor region

Clinical

• Slow growing
• Asymptomatic
• Gradual facial deformity and jaw expansion
• Bony hard, non tender ovoid swelling
• Egg shell crackling of bones on palpation in advanced cases
• Late feature: Perforation of bone + spread into soft tissue
• In maxilla – Expansion in sinus may mask true size of tumor

NB: Locally invasive but not metastasize

Diagnosis

• Incisional biopsy
• Radiology:
  • Usually multilocular, unilocular
  • Roots of associated teeth resorbed
  • Associated with unerupted teeth – particularly lower 8 (mimic dentigerous cyst)

Differential diagnosis

• Dentigerous cyst
• Odontogenic myxoma
• KCOT
• CEOT
• CCOT
• AOT

Pathogenesis

Main source of epithelium:

• Enamel organ
• Rests of Malassez
• Rests of Serres
• REE
• Lining of odontogenic cysts

Mechanism of growth and invasion:

• Overexpression of anti-apoptotic proteins – Bcl₂, Bcl_x
• Interface proteins enhance invasive properties – FGF, IL-1, IL-6, MMPs
• P53 downregulated

Histology

• Reversed nuclei polarity
• Tall columnar cells on periphery (ameloblasts)

Classification:

1. Follicular – Discrete, rounded islands or follicles, resemble enamel organ
2. Plexiform – Tangled mass of network of anastomosing strands + irregular masses
3. Acanthomatous – Squamous metaplasia and keratinization of stellate reticulum, keratin pearls
4. Desmoplastic – Extensive fibrosis of interstitial tissue, often anterior mandible
5. Cystic – Large cystic spaces lined by thin epithelium with basal palisading
6. Granular – Central, neoplastic cells – exhibit prominent cytoplasmic granularity
7. Basaloid – Similar to basal cell carcinoma

Management

• Surgical excision with margin of 1.5-2cm of normal bone
• + Reconstruction (Mandible – Titanium/stainless steel, Maxilla – Obturator)
• Good prognosis
• Can recur

Difference between ameloblastoma and ameloblastic fibroma

Ameloblastic fibroma	Ameloblastoma
Younger (1st and 2nd decade)	Older (4th and 5th decade)
Encapsulated	Non encapsulated
Inductive margin	No inductive margin
Not invasive	Invasive
Mixed: Epithelial and mesenchymal tissues	Odontogenic epithelium
Conservative – wide excision	Wide excision (1.5-2cm bone)
1 histologic subtype	7 histological subtypes
Common in maxilla	Common in mandible

Picture