Odontogenic Cysts and Tumors

Introduction

• A cyst is an epithelium lined sac containing fluid or semifluid material

• The epithelial cells first proliferate and later undergo degeneration and liquefaction

• Grow by expansion, causing displacement of adjacent teeth

Odontogenic cysts• Originate from residues of the tooth-forming organ• Derived from 3 origins:

- epithelial rests of Serres: odontogenic keratocyst, developmental lateral periodontal and gingival cysts

- reduced enamel epithelium : dentigerous, eruption and paradental cyst

- rests of Malassez : radicular cysts

Radicular Cysts

•Subdivided into : ApicalLateral Residual

•Causes: Develops from a preexisting periapical granuloma, Related to the apex of a nonvital tooth

Clinical features

• High incidence in anterior maxillary teeth

• Usually symptomless

• When enlarged cause expansion of the alveolar arch and may discharge through a sinus

• The rate of expansion 5mm/year in diameter

Histopathology

• Lined by non-keratinized stratified squamous epithelium

• Chronically inflamed fibrous tissue capsule

• Newly formed cysts have irregular epithelial lining with variable thickness. Becomes regular and even in thickness

• The connective tissue capsule becomes more fibrous, less vascular, and with less inflammatory cells

• Metaplasia of epithelial lining may give rise to mucous cells, and rarely ciliated respiratory epithelium

• In some cases the lining contains hyaline eosinophilic bodies, Rushton bodies

• Common cholesterol crystals deposits, which form clefts.

• Cholesterol crystals result from hemorrhage and breakdown of RBCs

Radiographic features

• Round radiolucency at the root apex

• Well defined, surrounded by radiopaque margin

• 40 % of apical radiolucencies are cystic

Contents

• Hypertonic fluid containing:-breakdown products of epithelial, inflammatory, connective tissue elements-serum proteins (5-11 g/dl), Igs higher than serum-water and electrolytes-cholesterol crystals

Residual cyst

• It is a radicular cyst that is retained after the extraction of the related tooth

• May continue growth causing significant bone resorption

Dentigerous cyst

• Encloses part or all of the crown of an unerupted tooth

• Develops from proliferation of the reduced enamel epithelium

• Eruption cyst arises in an extra-alveolar location

Radiographic examination

• Well-defined, unilocular, radiolucent, related to the crown

• Associated with impacted or delayed eruption (most commonly lower 8, upper 3)

Clinical features

• Twice as common in males• Twice as common in mandible• Usually asymptomatic • Large cysts tend to expand the outer plate

Histopathology

• Lining is a thin, regular, 2-5 cells thick, non-keratinized, stratified squamous or cuboidal

• Fibrous CT capsule free from inflammatory cell infiltration

• Occasional cholesterol clefts

Odontogenic keratocyst

• uncommon • 2nd to 3rd decades, or fifth decade• More common in males• Asymptomatic

• Multiple cysts are associated with naevoid basal cell carcinoma syndrome (Gorlin syndrome)

Radiographic features

•3rd molar and ramus of mandible area favored

•Well-defined radiolucency

•Can displace and resorb teeth

•Uni or multi locular

Histopathology

• wall is thin, regular, 5-10 cells thick stratified squamous epithelium

• Characteristic folded wall• Basal cell layer is well defined, contains

columnar or cuboidal cells • Sudden transition between stratum spinosum

and surface cells

Histopathology

• Thin fibrous capsule free from inflammatory cells

• High recurrence due to rupture

• Cyst contains keratinous debris, white cheesy material, protein level 4 g/dl

Gorlin Syndrome

• Gorlin syndrome: autosomal dominant, uncommon

• Manifestations:Skin: multiple naevoid basal cell carcinomasOral: multiple odontogenic keratocystsSkeletal: rib, vertebral anomalies. Polyductyly, cleft lip/palateCNS: calcified falx cerebri brain tumors

Gingival cyst

• Common in neonates

• Also knows as Bohn’s nodules or Epstein pearls

• Disappear by 3 months of age

• Arise from remnants of dental lamina, form keratinizing cysts

Developmental lateral periodontal cyst

• Uncommon

• Canine and premolar region of the mandible

• Derived from either reduced enamel epithelium or rests of dental lamina

• Occasionally multi locular

• Radiographically: well-defined radiolucency

• Large cysts can displace teeth and cause expansion

• Histologically: Lined by non-keratinized squamous or cuboidal epithelium

Paradental cyst

• Arises alongside an unerupted third molar involved with pericoronitis

• Radiographically: well-defined radiolucency related to the neck of the tooth

• Inflammatory origin stimulating proliferation of reduced enamel epithelium

Glandular odontogenic cyst

• Rare• occur in the anterior part of the mandible• Slow growing, painless• Histology: lined by varying thickness of

epithelium• Potentially aggressive, locally invasive with

tendency to recur

Odontogenic Tumors

Odontomes• Definition: non-neoplastic developmental

anomaly or malformation that includes enamel and dentine

• Types:1. Invaginated2. Evaginated3. Enamel pearl (enameloma)4. Double tooth5. Complex odontome6. Compound odontome

Invaginated odontome

• Invagination of the enamel organ into the dental papilla early in odontogenesis

• Permanent maxillary lateral incisor

• Three main types:1: confined to the crown2: extends into the root3: extends through the root apex

Histopathology

• Enamel and dentin lining the cavity are often defective and poorly mineralized

• The cavity is occupied with food debris and bacteria

Evaginated odontome

• Uncommon• Extra cusp like tubercles• Easily fractured, exposing the pulp

Complex odontome

• Disorderly arranged dental tissues

• Limited growth potential

• 2nd and 3rd decades, in the molar region of the mandible

• Painless, slow-growing

Radiographic examination

• well-defined radiolucent lesion, proceeds to radiopaque

• When mature it is surrounded by a translucent zone

Histopathology

• Developing lesions contain varying amounts of soft tissue and show features of stages of odontogenesis

Compound odontome

• Consists of numerous small denticles• 1st and 2nd decades of life and in anterior maxilla• Less growth potential than the complex type

Radiographic examination

• Mixed radiopaque/radiolucent bodies

Ameloblastoma

• Rare• Benign, locally invasive• Derived from odontogenic epithelium• More common in africans • Two variants: unicystic peripheral• 80% occur in mandible

Radiographic examination

• Multiloculated radiolucency, resorption of roots around it

• May become associated with unerupted 3rd molars

Histopathology

• 2 patterns:• Follicular: epithelium arranged into discrete

follicles resembling tooth germ• Plexiform type: epithelium is arranged in

tangled network and irregular masses

• The ameloblast-like cells express amelogenin, however, enamel and dentine are not formed

• Behavior: locally invasive, infiltrate cancellous bone without bone destruction initially

• High recurrence rate

Unicystic ameloblastoma

• Occur at younger age than other variants• Mainly in mandibular third molar region

• Histologically: ameloblastomatous lining with reversed polarity nuclei

• Radiographically: unilocular radilucency, usually associated with an unerupted tooth

• distinguishable from dentigerous cyst on by histopathological examination

Squamous odontogenic tumor

• Rare• Radiographically: well-circumscribed

radiolucency • Sclerotic border associated with roots of teeth• Histologically: irregularly shaped islands of

well-differentiated squamous epithelium in a stroma of mature fibrous tissue

• Derived from epithelial cells of Malassez.

Calcifying epithelial odontogenic tumour

• Rare• Benign• Wide age range• Mandible > maxilla• Mostly seen in molar and premolar region• 50% associated with an unerupted tooth• Some extraosseous case have been reported

Radiographic features

• Irregular radiolucent area• May or may not be clearly demarcated• Contains radiopaque bodies due to

calcification• Less aggressive than ameloblastoma

Histopathology

• Sheets and strands of polyhedral epithelial cells

• Abundant eosinophilic cytoplasm• Prominent intercellular bridges• Nuclear pleomorphism

Adenomatoid odontogenic tumour

• Presents usually in 2nd or 3rd decades• Majority in the anterior maxilla • Slowly growing swelling

Radiographic features

• Well defined radiolucency• Faint radiopacities due to calcifications• May simulate a dentigerous cyst _often

associated with an unerupted tooth

Histopathology

• Well encapsulated lesion• Maybe partly or wholly cystic• Central spaces contain eosinophilic material• Small foci of calcification

Ameloblastic fibroma

• Rare• Benign• Neoplasm of epithelial and mesenchymal

elements• Well circumscribed

Histopathology

• Proliferating strands of odontogenic epithelium in highly cellular fibroblastic tissue with peripheral layer of columnar cells

• Appearance similar to ameloblastoma

Calcifying cystic odontogenic tumour

• Grossly cystic• Mostly intraosseous• Radiographically: well-defined, uni or multi

locular, radiolucent, with radiopaque areas

Histopathology

• Basal layer of ameloblast-like cells, masses of swollen keratinized epithelial cells (ghost cells)

Odontogenic fibroma

• Derived from mesenchymal dental tissues

• 2 types:• Central type: uncommon, well demarcated,

cementum-like and dentine-like foci• Peripheral type: fibrous epulis, fibrous tissue

with cementum or dentinoid material

Odontogenic myxoma

• Locally invasive• More common than odontogenic fibroma• Radiographically:

Multilocular (soap-bubble appearance)Well definedRoots show resorption

Histopathology

• Non-encapsulated Infiltrative growth patternStellate cells with anastomosing processes

Cementoblastoma

• Mostly patients under 25 years of age• Usually molar and premolar area of mandible• Attached to the root of the tooth - vital• Slowly enlarging, sometimes causing pain

• Radiographically: well demarcatedmottled, radiopaque radiolucent margin, root resorption

• Histologically: cementum-like tissue, surrounded by sheets of uncalcified matrix