Ameloblastoma

Dr. Gaurav S. Salunkhe2nd MDS

Oral & Pathology

Ameloblastoma Clinical Case Presentaion

Introduction Ameloblastoma – English word amel, meaning

enamel+ the Greek word blastoma meaning germ.

Odontogenic tumors represent a spectrum of lesion ranging from malignant(rare) and benign neoplasm to dental hematomas all arising from odontogenic residues ie. Odontogenic epithelium and/or ectomysenchyme.

Occasionally an odontogenic tumor develops from a pre-existing developmental cyst (AOT, Ameloblastoma from dentigerous cyst)

Biopsy No. 107/13

Date: 25/03/2013

Case No. 884618

Ref.by: Dr. Bharat Department : OS

Name of the Patient: Kosha Gandhi

Age : 30yrs Sex: Female

Chief Complaint: swelling on the right side of lower jaw since 1 year.

Provisional Diagnosis: Ameloblastoma.

Extra-oral examination

Extra_oral

Intra-oral examination

Panoramic X-Ray

Macroscopic pathologyWe received hemi-mandible of right side

4x

10x

40x

Epithelial network

Cystic degeneration

Bone

Bone

Bone

DIAGNOSISBased on histological features the diagnosis

was given as Plexiform Ameloblastoma.

Ameloblastoma (adamantinoma, adamantoblastoma, multilocular cyst)

It is a true neoplasm of enamel organ type tissue which does not undergo differentiation to the point of enamel formation.

Defined as: ‘USUALLY UNICENTRIC, NONFUNTIONAL, INTERMITTENT IN GROWTH, ANATOMICALLY BENIGN AND CLINICALLY PERSISTENT’. By Robinson.

The term ameloblastoma was suggested by Churchill in 1934 to replace the term Adamantinoma, coined by Malassez in 1885.

Pathogenesis The earlier workers noted the resemblance

between the odontogenic apparatus and the ameloblastoma and suggested that the neoplasm has derived from a portion of this apparatus or from cells potentially capable of forming dental tissues.

Most authors believed that the ameloblastoma to be of varied origin, thus the tumor conceivably may be derived from

1. Cell rest of the enamel organ (remnants of the dental lamina, Hertwig’s sheath, the epithelial rest of Malassez).

2. Epithelium of odontogenic cysts. (dentigerous cyst)

3. Disturbance of developing enamel organ.4. Basal cell of the surface epithelium of the

jaw.5. Heterotopic epithelium in other parts of

the body, specially the pituitary gland.

Biological types Ameloblastoma

Unicystic Multicystic Peripheral

Unicystic ameloblastoma The unicystic ameloblastoma represent those cystic

lesion that shows clinical, radiographic, or gross features of a jaw cyst, but on histologic examination shows a typically ameloblastic epithelium.

The lining part of the cavity may or may not show luminal and or mural tumor growth.

It is variant of ameloblastoma comprising of 10% to 15% of all intra bony ameloblastoma.

The exact histogenesis is not clear.It has been suggested that it arise from as a result

of neoplastic transformation of the epithelial lining of dentigerous cyst or any other type of dental cyst.

A high percentage of these lesions are associated with impacted tooth and most commonly cited provisional diagnosis is dentigerous cyst.

The recurrence rate is low, and thus indicating less aggressive

Unicystic ameloblastoma is characterized by one or more of the following features:

1. Vickers & Gorlin criteria 2. Nodules of tumor projecting intraluminal.3. Epithelium proliferating into connective

tissue.4. Islands of ameloblastoma occurring isolated in

connective tissue wall.

In some instances, the ameloblastic epithelium may be proliferative, with extension of the ameloblastic epithelium into the lumen of the cystic cavity. This feature has been termed as intraluminal proliferation.

This growth resembles Plexiform ameloblastoma, thus some lesion have been referred to as Plexiform unicystic ameloblastoma.

Ackermann classification of UA 1988

Group 1- Luminal unicystic ameloblastoma.Tumor confined to the luminal surface of the

cyst.Group 2- Intra-luminal unicystic

ameloblastoma.Nodular proliferation into the lumen without

infiltration of tumor cells into the connective tissue wall.

Group 3- Mural unicystic ameloblastoma.Invasive islands of ameloblastomatous

epithelium in the connective tissue wall not involving the entire epithelium.

Unicystic ameloblastoma Clinical features:1. Mostly seen in younger individuals.2. Mostly seen in mandible.3. Posterior region. Molar-Ramus region

Radiographic features:1. Well defined, radiolucent lesion, with

minimal peripheral sclerotic border.2. Mimics dentigerous cyst.3. Associated with impacted/unerupted 3rd

molar.4. In advance stage thinning of cortical bone

can be seen.

Peripheral ameloblastoma Peripheral ameloblastoma is a

uncommon/rare type of odontogenic tumor.It develops in the soft tissue of the gingiva

and mucosa.It exhibits an innocuous clinical behaviour.It is non-invasive. It accounts for 1-5% of all ameloblastoma.

Peripheral ameloblastoma Clinical features:Mostly seen in younger individual.Males > Females.Mandible> Maxilla.Mostly seen in premolar region.The lesion appears as nodule on the

gingiva or mucosa.Size ranges from 3mm– 2cm in diameter.Recurrence is uncommon, except when it is

incompletely excised.

Honey comb

Histological types

Ameloblastoma

Plexiform

Acanthomatous

Granular Basal cell type

Desmoplastic

Follicular

Histology The epithelial component of the neoplasm proliferate

to form disconnected islands, cords, and strands within the collagenized fibrous connective tissue stroma.

In higher magnification, the darkly staining periphery is composed of tall columnar cells with hyperchromatic nucleus.

The nucleus tends to be round/oval in shape, and the nuclei of the adjacent cell are roughly in the same location within the cytoplasm.

The nuclei are oriented away from the basement membrane, with small clear vacuoles between the nucleus and the basement membrane.

Vickers & Gorlin criteria 1970

Tall columnar cell. Hyperchromatic nucleus.Paliasded nuclei.Reveres polarity of the nuclei.

Sub-nuclear vacuole formation.

Follicular ameloblastoma: Composed of many small discrete islands of

tumor composed of peripheral layer of cuboidal or columnar cells.

Nuclei are generally well polarised.The cells resemble ameloblasts or pre-

ameloblasts.These enclose a central mass of polyhedral,

loosely arranged cells resembling the stellate reticulum.

Plexiform ameloblastoma: The ameloblast like cells are arranged in

irregular masses, or more frequently, as a network of interconnected strands of cells.

Each of these strands is bound by a layer of tall columnar cells, between these layers may be found stellate reticulum like cells, these stellate reticulum like tissue is less prominent in Plexiform ameloblastoma than in the follicular ameloblastoma.

Acanthomatous ameloblastoma:The cells occupying the position of the

stellate reticulum undergo squamous metaplasia.

Sometimes with keratin formation in the central part of the tumor island.

keratin formation

Granular ameloblastoma:There is marked transformation in the

cytoplasm if the cells.The cytoplasm is very coarse, granular,

eosinophilic.

Basal cell type of ameloblastoma:It resembles the basal cell carcinoma of the

skin.It is rarest histological subtype.The epithelial cells are more primitive and

less columnar, and are arranged in sheet, no stellate reticulum like cell are present in the center of the nest.

Desmoplastic ameloblastoma :Half of the Desmoplastic ameloblastoma are

located in the maxilla, and the vast majority occur in the anterior or premolar portion of jaws.

This is in contrast to classical type of ameloblastoma, which are found in the posterior region of mandible.

Maxillary lesion are more insidious than mandibular tumors owing to the proximity of vital structures and maxillary sinus.

Also, the thin cortical bone of the maxilla forms a weak barrier for the spread of the tumor.

Desmoplastic ameloblastoma :Dense collagen stroma, may be hyalinised or

hypocellular.Has greater tendency to grow in thin strands and

cords of epithelium rather than island like pattern.The epithelial component is almost compressed

and fragmented by the dense hyalinised stroma.The peripheral cells are flattened or cuboidal

rather than tall columnar in appearance. Central cells are often scanty.Reverse polarity and subnuclear vacuolisations is

difficult to recognize.

Dense collagen stroma

Compressed epithelial component

Reichart et al. Follicular type had the highest rate of

recurrence, while acanthomatous type has least rate of recurrence.

Plexiform is intermediate

Treatment The type of T/t that have been used

include 1. Radical excision.2. Conservative surgical excision.3. Curettage. ( least desirable – highest rate

of recurrence )4. Electrocautery. 5. Radiation therapy. 6. Combination of surgery & radiation.

REFRENCES:Text book of oral pathology- Shafer 5th

edition.

Text book of oral & maxillofacial pathology- Neville 3rd edition.

Color atlas of oral pathology- Goro Ishikawa

Manual of oral pathology- Dr. Anand Tegginamani.