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AMELOBLASTOMA

Odontogenic tumors comprise a complex group of lesions with varied histopathological and clinical features.

Some tumors are true neoplasms, while some are hamartomas (developmental malformations).

Some are composed only of odontogenic epithelium, while many are mixed i.e. both epithelium and mesenchyme, while some are composed only of mesenchyme

 

 

 

TUMORS OF ODONTOGENIC EPITHELIUM: –

1. Ameloblastoma

2. Calcifying epithelial odontogenic tumor

3. Adenomatoid odontogenic tumor

4. Squamous odontogenic tumor

5. Clear cell odontogenic tumor

 

TUMORS OF ODONTOGENIC EPITHELIUM & MESENCHYME WITH / WITHOUT DENTAL HARD TISSUE FORMATION: –

1. Ameloblastic fibroma & Ameloblastic fibrosarcoma.

2. Ameloblastic fibro odontoma

3. Odontoameloblastoma

4. Odontoma – Compound & Complex

 

TUMORS OF ODONTOGENIC MESENCHYME WITH / WITHOUT DENTAL HARD TISSUE FORMATION: –

1. Odontogenic fibroma

2. Odontogenic myxoma

3. Cementoblastoma

4. Granular cell odontogenic tumor

 

AMELOBLASTOMA

The ameloblastoma is a true neoplasm of enamel organ type tissue which does not undergo differentiation to the point of enamel formation. According to Robinson, ameloblastoma is a tumor that is “usually unicentric,non-functional ,intermittent in growth, anatomically benign and clinically persistent.

Most common odontogenic neoplasm, derived from odontogenic epithelium.

Slowly growing, locally aggressive, benign neoplasm.

Occurs in 3 different types with differing clinical, radiological and histological features.

1. CONVENTIONAL / MULTICYSTIC

2. UNICYSTIC

3. PERIPHERAL

 

AMELOBLASTOMA – CONVENTIONAL

CLINICAL FEATURES: –

Age incidence: 3rd & 4th decades.

Sex incidence: Slightly more in males.

Site predilection: 80% ameloblastomas occur in posterior  mandible, followed by maxillary molar         region.

 

 

Signs & symptoms: –

 

 

 

 

 

 

 

 

 

 

 

 

Slowly growing, painless, hard bony swelling or expansion of jaw.

Thinning of cortical plates produces “Egg shell crackling”.

Other symptoms – Tooth mobility  root resorption and paresthesia if inferior alveolar nerve is affected.

 

 

RADIOLOGICAL FEATURES: –

 

Typically rounded, well defined multilocular radiolucency with scalloped margins.

When loculations are large, the appearance is called as “SOAP BUBBLE”appearance.

When loculations are smaller, the appearance is called “HONEY COMBED”appearance.

Buccal & lingual cortical plates are expanded.

Roots of adjacent teeth displaced / resorbed.

As it spreads through medullary spaces, radiographic margins are not accurate indication of bone involvement.

 

 

 

 

 

 

 

 

 

DIFFERENTIAL DIAGNOSIS: –

ODONTOGENIC KERATOCYST

FIBROUS DYSPLASIA

OSSIFYING FIBROMA

CENTRAL GIANT CELL GRANULOMA

HISTOPATHOLOGICAL FEATURES: -Many subtypes are seen.

1.       FOLLICULAR

2.       PLEXIFORM

3.       ACANTHOMATOUS

4.       GRANULAR CELL

5.       DESMOPLASTIC

6.       BASAL CELL TYPE

7.       CLEAR CELL Type

 

AMELOBLASTOMA (FOLLICULAR)

 

 

Islands of epithelium resemble dental organ surrounded by mature connective stroma.

Individual follicles show central mass of stellate reticulum like cells surrounded by a single peripheral layer of ameloblast like cells.

Nuclei of peripheral cells are reversely polarized.

Within the islands, cyst formation is common.

 

AMELOBLASTOMA (PLEXIFORM)

 

 

Instead of islands, long, anastomosing cords and occasional sheets of epithelial cells bounded by columnar / cuboidal cells.

Cells within cords are more loosely arranged than peripheral cells.

Supporting stroma is loose and vascular.

Cyst formation occurs, not inside follicles, but in surrounding stroma.

 

AMELOBLASTOMA (ACANTHOMATOUS)

 

 

Central area of follicles show extensive squamous metaplasia, often associated with keratin formation.

DOEAS NOT INDICATE A MORE AGGRESSIVE COURSE OF TUMOR.

Can be confused with squamous cell carcinoma.

 

 

AMELOBLASTOMA (GRANULAR CELL)

 

 

Follicles / sheets of cells show granular cell change.

These cells have abundant cytoplasm filled with eosinophilic granules.

Seen in younger persons and appears to be more aggressive clinically.

 

 

AMELOBLASTOMA (DESMOPLASTIC)

 

 

This variant is composed of small islands / cords of odontogenic epithelial cells surrounded by a dense, collagenized stroma.

Peripheral ameloblast like cells are missing / inconspicuous around the islands / cords.

Occurs in anterior jaw and radiologically looks like a fibro-osseous lesion due to mixed opacity & lucency.

 

AMELOBLASTOMA (BASAL CELL)

 

 

Least common type.

Composed of nests / sheets of hyperchromatic basaloid cells.

No stellate reticulum present centrally and peripheral cells tend to be cuboidal rather than tall columnar.

 

TREATMENT: –

Can vary from simple enucleation to curettage to en bloc resection.

As lesion spreads through medullary spaces, simple enucleation can leave islands of tumor within the jaws, leading to recurrence.

Marginal resection is the optimal method.

Rarely can undergo malignant transformation.

 

UNICYSTIC AMELOBLASTOMA

Controversy, whether it arises de novo or as neoplastic transformation of odontogenic cyst lining.

CLINICAL FEATURES: –

Age incidence: Young individuals.

Sex incidence: males.

Site predilection: 90% cases occur in post  mandible.

Signs & Symptoms: Asymptomatic swelling of jaws. Many lesions contain a tooth inside.

 

RADIOLOGICAL FEATURES: –

Typically seen as well defined, unilocular ‘lucency, many times surrounding the neck of impacted 38 or 48 – impossible to distinguish from dentigerous cyst.

Occasionally, may be seen unassociated with teeth – then they nay be diagnosed as OKC or a radicular cyst.

 

DIFFERENTIAL DIAGNOSIS: –

Odontogenic cysts like – Dentigerous, OKC, radicular etc.

Odontogenic tumors like – Ameloblastoma, AOT, CEOT etc.

HISTOPATHOLOGICAL FEATURES: –

Three variants are recognized.

1. LUMINAL UNICYSTIC

2. INTRALUMINAL UNICYSTIC

3. MURAL UNICYSTIC

UNICYSTIC – LUMINAL

 

 

Tumor is confined to luminal surface of cyst.

Seen as fibrous cyst wall with lining comprised totally / partially of ameloblastic epithelium, showing a basal layer of columnar / cuboidal reversely polarized cells.

Overlying epithelial cells are loosely adhesive, resembling the stellate reticulum of dental organ.

 

UNICYSTIC – INTRALUMINAL

 

 

This variant shows the tumor from cyst lining protruding into the lumen of cyst.

Intraluminal projections resemble plexiform ameloblastoma in most cases, though not always.

 

UNICYSTIC – MURAL

 

 

In this type, the fibrous wall of the cyst is infiltrated with typical follicular / plexiform ameloblastoma.

Believed to be more aggressive than other two variants.

AMELOBLASTOMA (PERIPHERAL)

 

 

Typically presents as non ulcerated, sessile / pedunculated gingival mass.

Must be differentiated from other more common gingival swellings.

 

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