OVERVIEW n General consideration
n Classification
n Description of some common and important odontogenic tumors.
n Odontogenic tumors comprise a complex group of lesions with varied histopathological and clinical features.
n Some tumors are true neoplasms, while some are hamartomas (developmental malformations).
n Some are composed only of odontogenic epithelium, while many are mixed i.e. both epithelium and mesenchyme, while some are composed only of mesenchyme
n CLASSIFICATION
A. TUMORS OF ODONTOGENIC EPITHELIUM: -
1. Ameloblastoma
2. Calcifying epithelial odontogenic tumor
3. Adenomatoid odontogenic tumor
4. Squamous odontogenic tumor
5. Clear cell odontogenic tumor
B. 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
C. TUMORS OF ODONTOGENIC MESENCHYME WITH / WITHOUT DENTAL HARD TISSUE FORMATION: -
1. Odontogenic fibroma
2. Odontogenic myxoma
3. Cementoblastoma
4. Granular cell odontogenic tumor
AMELOBLASTOMA
n Most common odontogenic neoplasm, derived from odontogenic epithelium.
n Slowly growing, locally aggressive, benign neoplasm.
n 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: -
n Slowly growing, painless, hard bony swelling or expansion of jaw.
n Thinning of cortical plates produces “Egg shell crackling”.
n Other symptoms – Tooth mobility root resorption and paresthesia if inferior alveolar nerve is affected.
RADIOLOGICAL FEATURES: -
n Typically rounded, well defined multilocular radiolucency with scalloped margins.
n When loculations are large, the appearance is called as “SOAP BUBBLE” appearance.
n When loculations are smaller, the appearance is called “HONEY COMBED” appearance.
n Buccal & lingual cortical plates are expanded.
n Roots of adjacent teeth displaced / resorbed.
n 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.
- FOLLICULAR
- PLEXIFORM
- ACANTHOMATOUS
- GRANULAR CELL
- DESMOPLASTIC
- BASAL CELL TYPE
- CLEAR CELL TYPE
AMELOBLASTOMA (FOLLICULAR)
n Islands of epithelium resemble dental organ surrounded by mature connective stroma.
n Individual follicles show central mass of stellate reticulum like cells surrounded by a single peripheral layer of ameloblast like cells.
n Nuclei of peripheral cells are reversely polarized.
n Within the islands, cyst formation is common.
AMELOBLASTOMA (PLEXIFORM)
n Instead of islands, long, anastomosing cords and occasional sheets of epithelial cells bounded by columnar / cuboidal cells.
n Cells within cords are more loosely arranged than peripheral cells.
n Supporting stroma is loose and vascular.
n Cyst formation occurs, not inside follicles, but in surrounding stroma.
AMELOBLASTOMA (ACANTHOMATOUS)
n Central area of follicles show extensive squamous metaplasia, often associated with keratin formation.
n DOEAS NOT INDICATE A MORE AGGRESSIVE COURSE OF TUMOR.
n Can be confused with squamous cell carcinoma.
AMELOBLASTOMA (GRANULAR CELL)
- Follicles / sheets of cells show granular cell change.
n These cells have abundant cytoplasm filled with eosinophilic granules.
n Seen in younger persons and appears to be more aggressive clinically.
AMELOBLASTOMA (DESMOPLASTIC)
n This variant is composed of small islands / cords of odontogenic epithelial cells surrounded by a dense, collagenized stroma.
n Peripheral ameloblast like cells are missing / inconspicuous around the islands / cords.
n Occurs in anterior jaw and radiologically looks like a fibro-osseous lesion due to mixed opacity & lucency.
AMELOBLASTOMA (BASAL CELL)
n Least common type.
n Composed of nests / sheets of hyperchromatic basaloid cells.
n No stellate reticulum present centrally and peripheral cells tend to be cuboidal rather than tall columnar.
TREATMENT: -
n Can vary from simple enucleation to curettage to en bloc resection.
n As lesion spreads through medullary spaces, simple enucleation can leave islands of tumor within the jaws, leading to recurrence.
n Marginal resection is the optimal method.
n Rarely can undergo malignant transformation.
UNICYSTIC AMELOBLASTOMA
n 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: -
n Typically seen as well defined, unilocular ‘lucency, many times surrounding the neck of impacted 38 or 48 – impossible to distinguish from dentigerous cyst.
n 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: -
n Three variants are recognized.
1. LUMINAL UNICYSTIC
2. INTRALUMINAL UNICYSTIC
3. MURAL UNICYSTIC
UNICYSTIC - LUMINAL
n Tumor is confined to luminal surface of cyst.
n Seen as fibrous cyst wall with lining comprised totally / partially of ameloblastic epithelium, showing a basal layer of columnar / cuboidal reversely polarized cells.
n Overlying epithelial cells are loosely adhesive, resembling the stellate reticulum of dental organ.
UNICYSTIC - INTRALUMINAL
n This variant shows the tumor from cyst lining protruding into the lumen of cyst.
n Intraluminal projections resemble plexiform ameloblastoma in most cases, though not always.
UNICYSTIC - MURAL
n In this type, the fibrous wall of the cyst is infiltrated with typical follicular / plexiform ameloblastoma.
n Believed to be more aggressive than other two variants.
AMELOBLASTOMA (PERIPHERAL)
n Typically presents as non ulcerated, sessile / pedunculated gingival mass.
n Must be differentiated from other more common gingival swellings.
ADENOMATOID ODONTOGENIC TUMOUR
n Earlier, believed to be a variant of Ameloblastoma with glandular elements and was referred to as ADENOAMELOBLASTOMA.
n Now believed to be a separate entity and thought to arise from odontogenic epithelial cells.
CLINICAL FEATURES: -
Age incidence: Young individuals, 1st & 2nd decades.
Sex incidence: More in females, twice more.
Site predilection: Anterior aspect of maxilla.
Signs & symptoms:
n Small, asymptomatic lesion.
n Discovered accidentally during routine dental X-ray examination to ascertain cause for unerupted tooth.
n Larger lesions cause jaw expansion
RADIOLOGICAL FEATURES:
n Typical well defined unilocular ‘lucency attached to an impacted / unerupted tooth, usually canine (FOLLICULAR VARIETY).
n ‘Lucency extends past cervical region & must be distinguished from dentigerous cyst.
Extrafollicular – well defined ‘lucency not related to unerupted tooth.
n In both cases, ‘lucency may contain snowflake like radio opacities.
DIFFERENTIAL DIAGNOSIS: -
n Radiographic appearance can suggest following lesions for provisional diagnosis -
1. Unicystic ameloblastoma
2. CEOT
3. COC
HISTOLOGICAL FEATURES: -
n Lesion is composed of spindle shaped epithelial cells that form sheets, strands or whorls in a scanty stroma.
n Rosette like structures may show a central space which may be empty or contain some eosinophilic amyloid like material.
n Tubular duct like spaces are also seen which show a central space surrounded by reversely polarized cells.
CALCIFYING EPITHELIAL ODONTOGENIC TUMOUR
n Rare tumor, accounts for > 1% of all odontogenic tumors.
n Although odontogenic in origin, its histogenesis is uncertain.
n Tumor cells strongly resemble stratum intermedium of dental organ.
CLINICAL FEATURES: -
Age incidence: 3rd to 5th decades.
Sex incidence: Equal.
Site predilection: 75% cases occur in posterior mandible.
Signs & symptoms: Asymptomatic, slow growing swelling.
RADIOLOGICAL FEATURES:
n Commonly appears as a well defined, scalloped, uni/multilocular ‘lucency, usually associated with an impacted tooth.
n Lesion may also show presence of scattered radiopaque material within the ‘lucency.
DIFFERENTIAL DIAGNOSIS: -
- Odontogenic cysts like dentigerous, OKC, etc.
- Odontogenic tumors like Ameloblastoma, etc.
- Other bony lesion like Central giant cell granuloma, Aneurismal bone cyst etc.
HISTOLOGICAL FEATURES: -
n Tumor shows discrete islands / sheets of polyhedral epithelial cells in a fibrous stroma.
n Nuclei show lot of size variation, even giant nuclei can be seen.
n Tumor islands also enclose large areas of eosinophilic, amorphous, amyloid like material
n The cell outlines of tumor epithelial cells are distinct and intercellular bridges may be noted.
n The amyloid like material usually calcifies to form concentric rings (LEISEGANG RINGS).
ODONTOMA
n Most common odontogenic tumor.
n Considered hamartomas, rather than neoplasm.
n In a fully developed odontoma, mainly enamel and dentin along with variable amounts of pulp and cementum are seen.
CLASSIFICATION: -
n Odontomas are further sub classified into
- COMPOUND ODONTOMA
- COMPLEX ODONTOMA
n Both occur with equal frequency.
Compound – composed of multiple, small, tooth like structures.
Complex – composed of conglomerate mass of enamel and dentin with no anatomic relationship to tooth.
CLINICAL FEATURES : -
Age incidence: First 2 decades.
Sex incidence: None.
Site predilection: Anterior maxilla.
Signs & symptoms:
n Mostly asymptomatic, small, seldom exceeding the size of tooth missing in the region.
n Larger lesions may cause jaw expansion.
ODONTOMA (COMPOUND)
n Gross pathological specimen showing a mass of more than 20 tooth like malformed structures.
n ODONTOMA (COMPOUND)
RADIOLOGICAL FEATURES: -
n This type is composed of multiple, small tooth like structures.
n The entire mass appears surrounded by a radiolucent rim.
n An unerupted tooth is usually associated with both types of odontomes which impedes normal eruption of the tooth.
ODONTOMA (COMPLEX)
RADIOLOGICAL FEATURES:
n Complex odontoma comprises of a single conglomerate mass of tooth like material.
n It bears no anatomic resemblance to any tooth.
n Appears as a ‘opaque mass surrounded by a narrow ‘lucent rim.
ODONTOMA (COMPOUND)
HISTOLOGICAL FEATURES: -
n Microscopically, it shows discrete tooth like denticles in a fibrous stroma.
n Being a decalcified specimen, enamel appears as spaces around normal looking dentin and pulp which bear normal anatomic relationship to each other.
ODONTOMA (COMPLEX)
HISTOLOGICAL FEATURES: -
n Consist of largely tubular dentin enclosing clefts / hollow circular spaces that contained enamel prior to decalcification.
n Thin layer of cementum sometimes may be present at the periphery.
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