Ameloblastoma

By:

Mohamed Saber

Ameloblastoma

DefinitionEtiologyOriginTypesClinical features(incidence)Clinical presentaionRadiographic presentation Histopathological findingsDifferential diagnosistreatment

It is a benign but invasive epithelial odontogenicneoplasm.

Consisting of proliferating odontogenicepithelium lying in fibrous stroma

etiology

Unknown , but possible causal factors suggested :

Truama or inflamation

Oral infection,extraction,injury to teeth or jaws

Irritation resulting from eruption of the third molar

Origin of ameloblastoma

The precise point of origin of ameloblastoma is unknown ,the origin might be from:

Epithelial rests of serre or malassez

Epithelial lining of non neoplastic odontogeniccyst(dentigerous cyst)

Direct from oral epithelium

types

Conventional solid or multicystic 94%

Unicystic(mural) 5%

Peripheral or extraosseous 1%

incidence

It’s the most common epithelial odontogenicneoplasm.

It comprises about 1% of all oral tumors.

Mandible>maxilla 85%:15%

in mandible:

70% in molar-ramus area, 20%in premolar area,

10% in incisor region

incidence

In the maxilla:

Tumor found in the posterior region

Age predilection :

Fourth and fifth decades

The tumor can occur in children or in old age

Clinical presentation

In the early stages : ameloblastoma grows slowly &silently without clinical signs.

in advanced stages:

neoplasm expand cortical plates thinning of bone (egg shell crackling )erodes them invades the soft tissue

At this point ameloblastoma present clinically as a smooth surfaced local expansion of the jaw producing asymmetry.

Clinical presentation

Lesion may be composed of solid tumor,cysticareas,or booth.

Tipping or loosening of teeth,involvement of inf. Alveolar nerve may occur.

Draining sinuses,unhealed extraction sockets associated with granulation tissue within the socket,bleeding ,trismus& other dental problems may be the chief complain

Clinical presentation

Max. ameloblastoma:

Nasal obstruction is 1st symptoms

Potentially lethal if sinus involved or tumor invade the bone into soft tissues due to:

Bone is not compact, easily invaded

Proximity to: nasal cavity&sinuses

orbital&pharyngeal tissues

vital structures at base of skull

This factors also complicate comlete removal

Radiographic presentation

Ameloblastoma is osteolytic lesion

Unilocular or multilocul radiolucency

Multilocular lesion may be :

Honey combed (small loculation)

Soap bubble (large loculation)

Crtical bone may be spread &expanded or destroyed.

Unerrupted tooth may be present(resembling dentigerous cyst)

Radiographic presentation

Root resorption of associated teeth.

Maxillary tumors produce a monocystic cavity in most instances.

Histopathological findings

Ameloblastoma can be classified into:

Follicular ameloblastoma or plexiformameloblastoma.

Variant s of follicular ameloblastoma:

Cystic type

Basal cell type

Acanthomatous type

Dysmoplasatic type

Histopathological findings

Follicular ameloblastoma:

Made of epithelial follicles resembling enamel organ in mature fibrous c.t. stroma.

Epithelial follicles consist of peripheral tall columnar cells(ameloblast like cells)& central core of loosely arranged angular cells (the stellate reticulaum like cells)

Histopathological findings

Plexiform ameloblastoma:

The epithelium is arranged in a network of anastomosing strands and cords with the same cell layers as follicular ameloblastoma.

Differential diagnosis

Other odontogenic tumors:

Ameloblastic fibroma,odontogenic myxoma.

Non odontogenic tumors:

Central giant cell granuloma,aneurysmal bone cyst.

Odontogenic cysts:

Dentigerous cyst,odontogenic keratocyst

Treatment

Treatment of ameloblastoma ranges from conservative curettage to radicular resection.

Treatment varies according to site,size&characteristics of the ameloblastoma

Curettage

En-block resection

Segmental resection

curettage

It is the removal of the tumor by scraping it from the surrounding normal tissue.

It is the least desirable form of therapy.

Failure of curettage is due to extension of tumor cell nests beyond the clinical& radiographic margins of the lesion,therefore it is impossible to eradicate by scraping procedure.

En –block resection

It is removal of the tumor with a rim of uninvolved bone safe margin,but with maintaining the continuity of the jaw.

It is frequently used for ameloblastoma,althoughthere is a diffuse invasion of cancellous spaces of bone marrow by finger like projections,tumortissue doesn’t invade the haversian system of compact bone,thus compact bone of mandible can be eroded but it is less likely to be invaded.

Segmental resection

Segmental resection including hemimaxillectomy& hemimanibulectomy has been the most commonly used treatment for ameloblastoma.

Most authors who advocate this method have had the least number of recurrence.

Unicystic(mural) ameloblastoma

Its formed in the wall of a dentigerous cyst

Its ranked next to dentigerous cyst as the most frequently occuring pathologic pericoronalradiolucency.

The terms mural or unicystic are used to identify this type ,although unicystic ameloblastomacan occur in other locations &not contacted to teeth

Unicystic(mural) ameloblastoma

It represent about 5% of all ameloblastoma.The conventional ameloblastoma and mural ameloblastoma are similar in predilection for gender(males&females equally affected)& Site(mand. 3rd molar region)However the mural variety occur in younger age gp.(2nd &3rd decades)Can be related to other types of cyst(radicular,primordial,residual--,globulomaxillary)

Unicystic(mural) ameloblastoma

in early stage asymptomatic,undetected untilepericoronal radiolucency is seen on routine radiograph.

Slowly enlarged,slight non tender sweelingappear clinically.

If bone destruction occur,palpation discloses softer areas.

Unicystic(mural) ameloblastoma

Radiographically:

If haziness&thinning of hyperostoticradioopaque rim of pericoronal radiolucency

Tumor invade the capsule of the cyst &start to infiltrate the bone trabeculae .

management

Before undertaking surgical procedure of pericoronal radiolucency, differential diagnosis bet. mural(unicystic) &conventional ameloblastoma should be completed.

At surgery the cyst should be enucleated,and if mural mass is discovered flag it with suture to enable the pathologist for further investigation.

management

If pathologist examination establishes the mass as ameloblastoma that has not penetrated the basement membrane no further surgery is done.

If the neoplasm has penetrated the basement membrane more the bone should be removed with curettage.

In all cases careful periodic follow- up is always indicated.

Peripheral(extraosseous) ameloblastoma

Origin: basal layer of oral epith.&extraosseousportion of epith. Rests of serre.

Site: commonly affect gingiva & alveolar mucosa

mandible> maxilla

Micoscopically it looks like acanthomatous type of basal cell carcinoma of the skin.

Management: excision.

Behavior: less invasive than intraosseousameloblastoma.