Michael Castillo, MD

Odontogenic lesions may be often incidentally found when they are small.  However, when large, they may be associated with secondary infection or missing/impacted teeth.  As the lesion enlarges teeth may become misdirected and bone may become expanded. 

Modalities for diagnosing these lesions include screening dental intraoral x-rays, panorex and CT scans.  Panorex is the most useful, however it is important to remember that patients must remain sitting for several seconds and lesions outside focal length will not show up.  CT scanning is helpful for very large lesions and to determine if bone is eroded by lesion.

Odontogenic cysts are classified as developmental, inflammatory or pseudocysts (nonepithelial).  Developmental cysts may be further classified as odontogenic or nonodontogenic.  Odontogenic developmental cysts include follicular cysts, odontogenic keratocysts, eruption cysts, alveolar cyst of infants, gingival cyst of adults, and developmental lateral periodontal cysts.  Nonodontogenic cysts include nasopalatine duct cysts, midpalatal cyst of infants, and nasolabial cysts.  Inflammatory cysts include radicular cysts, periapical cysts, and lateral periodontal cysts.  Pseudocysts do not have an epithelial lining and include idiopathic bone cavities, aneurismal bone cysts, and mucus retention cysts. 

In contrast to odontogenic cysts, odontogenic tumors are classified by histogenesis and are divided into epithelial, mesenchymal and mixed tumors. 

Inflammatory cysts are the most common cysts of the jaw.  They are often initiated by dental disease, resulting after bacterial invasion of the dental pulp.  They are termed “radicular” cysts because they are associated with the root of the involved tooth.  When along apex of root they are known as “Periapical” cyst (65% of cysts).  When along the side of the root they are known as “lateral periodontal” cysts.  Treatment involves treating the source of infection, considering a root canal to remove necrotic pulpal tissue or extraction of the tooth.

Follicular cysts are also known as dentigerous cysts.   “Follicular” is a more correct term as it is felt to develop from the tooth follicles.  These are the second most common cyst (24%).    They are associated with the crown of unerupted teeth.  They form when fluid accumulates between the reduced enamel epithelium and the tooth crown.  Follicular cysts almost always involve permanent teeth - most frequently third molars and maxillary canines (often impacted). They are usually asymptomatic.  Males are affected more often than females.  Treatment is via enucleation and curettage. 

Odontogenic keratocysts (OKC) are diagnosed by histological diagnosis.  Clinically and radiographically they can appear like a follicular or radicular cyst.  They have a high recurrence rate which makes proper diagnosis key to treatment.  Males are affected more than females.  The mandible is affected more than the maxilla.  The mandibular third molar and ramus areas are most frequently involved.  There are specific histologic features that allow for OKC diagnosis, including:

-Thin squamous epithelium 6-8 cells thick

-Prominent columnar or cuboidal basal cell layer with dense nuclear staining

-Corrugated surface layer of parakeratin

-Thin connective tissue wall

-Satellite budding and outpouching of cyst lining

These histologic appearances can account for the lesion’s high recurrence rate.  On resection they are often filled with foul-smelling white exudate (similar to epidermoid cysts - which are also keratinizing).  Treatment is difficult with recurrence rates from 10 to 60%.   They are often multilocular lesions with thin and friable cyst lining and have higher mitotic rates than other cysts.  In addition the cyst may have epithelial “budding” that are left behind.  Also, the OKC may perforate the cortex and cystic epithelium that is left in soft tissue may be difficult to remove.   Initial treatment should begin with enucleation with curettage.  It is possible to attempt chemical curettage with Carnoy’s solution (tissue fixative with Etoh, chloroform and ferric acid).  If the lining is removed in fragments the recurrence rate can be greater than 50%.  If the lesion recurs, more aggressive treatment is warranted, such as marginal mandibular resection.

Basal cell nevus syndrome, which is also known as Gorlin’s syndrome, should be considered in patients who present with multiple keratocysts.  This is an autosomal dominant disorder with complete penetrance.  Clinical features include the following:

-Skeletal abnormalities
-Bifid ribs, fused vertebrae, scoliosis
-Soft-tissue abnormalities
-Multiple basal cell carcinomas
-palmar pitting
-epidermoid cysts
-Characteristic face with frontal and temporoparietal bossing of skull
-ocular hypertelorism
-calcified falx cerebri

Nonodontogenic cysts comprise 5% of jaw cysts.  They arise from epithelium trapped during development of oral cavity and face and are also known as fissural cysts.   They are not associated with tooth development.   Because no fusion occurs during embryological development, the mandible will not have any of these cysts.  The nasopalatine duct cyst (a.k.a incisive canal cyst) is the most common.  It forms from cystic degeneration of the oronasal ducts connecting the nasal cavity to oral cavity during development.   It will appear as a round to ovoid or heart-shaped, radiolucent, lesion lying between the central incisors.   The midpalatal cyst occurs in the midline of the hard palate and is usually asymptomatic.  The nasolabial cyst is a soft tissue cyst of the upper lip.  It is almost exclusive to females and is treated with local excision or intranasal marsupialization. 

Nonepithelial cysts (pseudocysts) are typically termed “cysts” but have no epithelial lining.  Idiopathic bone cavities (solitary bone cyst) are theorized to develop after hemorrhage and subsequent degeneration of a clot without bony filling.  This leads to an empty bone cavity.  Most often the posterior body or ascending ramus is involved. Teenagers are most commonly affected.  It will appear as a “scalloped” lesion as it grows around and between tooth roots.  It is treated with a biopsy to rule out other lesions.  Aneurismal bone cysts are felt to be a reactive process, secondary to a primary lesion of the bone that initiates a vascular malformation.  They are firm, nonpulsatile lesions and are often painful.  It sill appear as a lesion with sclerotic/irregular bone margins.  Treatment is with enucleation. 

Ameloblastomas are the most common epitelial odontogenic tumors.  They are benign, but infiltrative lesions characterized by slow growth capable of massive deformity.  They can be considered the intraoral analogue of the cutaneous basal cell carcinoma. The posterior mandible is the favored site, but 20% may occur in maxilla.  17% are associated with an impacted tooth or dentigerous cyst.  Several histologic variations are noted (cystic, acanthomatous, plexiform, basal cell, granular cell) but have no prognostic significance.  They may rarely metastasize hematogenously - known as “metastasizing ameloblastoma” or ameloblastic carcinoma. 

Ameloblastomas may be solid or multicystic (92%), peripheral (2%) or unicystic (6%).  Solid ameloblastomas are generally slow growing, without eroding through mucosa.  It is rarely painful and treatment has a recurrence rate of greater than 50% if only treated with enucleation/curettage.  Rather it is recommended to resect these lesions with 1 - 1.5 cm margins.  Peripheral ameloblastoma occurs in the soft tissue overlying alveolar bone.  Histologically it resembles the intraosseous forms, but is much less aggressive than solid/multicystic ameloblastoma.  Treatment is by local excision through the periosteum.  Unicystic ameloblastoma typically involves a young population.  It will appear initially as an odontogenic cyst and is therefore often treated via only enucleation/curettage.  Careful follow up is necessary as it may recur 10-20% of time.

Calcifying epithelial odontogenic tumors (CEOT) are also known as Pindborg tumors.  They are histologically distinct from ameloblastomas and most present as asymptomatic swellings.  They are typically slow growing lesions and most often affect patients of middle ages.  Radiographically they appear as a diffuse lucency with scattered flecks of calcification.  Treatment is similar to ameloblastoma with recommendation for 1 cm margins. 

Odontogenic adenomatoid tumor are also known as adenoameloblastoma or adenomatoid odontogenic tumor.  This was originally felt to be a subtype of amelloblastoma, though clinically, microscopically and behaviorally it is now known to be different.  It is noninvasive and some classify it as a hamartoma and not a neoplasm.  Histologically it has a ductlike arrangement of epithelial cells.  Typically younger patients are involved.  Women are more frequently involved than men.  Two-thirds are found in the maxilla, most frequently near the maxillary canines.  Radiographically they appear as a lucency with focal radiopacities.  Treatment is with enucleation and recurrence is very rare. 

Odontogenic myxoma is a benign tumor but may be aggressive.  It involves the mandible  as frequently as the maxilla.  Radiographically it appears as a honeycombed, radiolucent lesion.  It can mimic dental pulp histologically.  In fact, pathologists may err in calling developing dentition a myxoma.  It is important for the pathologist to understand the clinical and radiographic presentation of the patient to prevent such an error.

“Cementoma” is a broad classification for lesions that result from cementum.  All are benign.  Cementoblastoma (true cementoma) is a neoplasm of cementoblasts that produces a mass of cemental tissue at the tooth root.  The mandible is more often affected than the maxilla.  It appears as a well circumscribed, dense, radiopaque lesion, attached to the tooth root.  Treatment is by tooth removal – these lesions do not recur.

Odontomas can be considered as a “Compound” odontoma  (resembles normal teeth) or a

“complex” odontoma (disorganized).   Histologically they are composed of enamel, dentin, pulp and connective tissue.  Treatment is by enucleation.

Ameloblastic fibromas often affect children and young adults (mean age 12).  They often affect mandibular molars and can be mistaken for ameloblastoma by the pathologist.  The pathologic key is that unlike ameloblastoma this lesion has epithelial and mesenchymal (fibroma) components.  It is well demarcated from surrounding bone.  Recurrence after treatment is uncommon.

Related jaw lesions, for the purpose of this discussion, include:
-Fibrous dysplasia
-Ossifying fibroma
-Giant cell lesions

Fibrous dysplasia (FD) occurs when normal medullary bone has been replaced by an abnormal fibrous connective tissue proliferation.  Monostotic fibrous dysplasia occurs in only one bone (more common - 80% of cases) while polyostotic fibrous dysplasia occurs when  more than one bone is involved.  McCune-Albright syndrome is polyostotic FD with cutaneous melanotic pigments and endocrine abnormalities (often precocious sexual development in females).  Clinically, patients are asymptomatic with slow enlargement of the involved bone.  The maxilla is more often involved than the mandible.  Most often the buccal cortical plate expands, while the palate and lingual surfaces appear uninvolved.  Onset is often in the first or second decade of life.  Malignant transformation (<1%) when it occurs is suggested by rapid enlargement of the lesion or new pain.  Classic radiographic description is of a radiopaque lesion with numerous bony trabecula giving a “ground-glass” appearance.  FD has very poorly defined margins.  Histologically there is a cellular, fibrous connective tissue proliferation with irregularly shaped trabeculae of immature bone.  It shares many features with ossifying fibroma, therefore, the physician must consider clinical, radiographic and histologic features together for proper diagnosis.  Treatment of FD varies.  Typically FD stabilizes or slows after puberty.  Small lesions may only require biopsy to rule out other lesions and periodic follow up.   FD to the orbital region may require optic nerve decompression if there is progressive or rapid vision loss.  Surgery for FD may include resection of bone with recontouring and replantation to provide proper contour. 

Ossifying fibroma is a benign neoplasm from undifferentiated periodotal ligament tissues.  Clinically, it is a slow growing, expansile lesion that replaces normal bone as it enlarges.  It is most common to the body of the mandible with a peak incidence occurring at 20-40 years old.  Only rarely will patients present with pain, paresthesia, or mucosal ulcerations.  Most commonly it presents as a single lesion.  Radiographically, in contrast to FD, there is a well-circumscribed border.  It can begin as a radiolucent lesion that becomes radiopaque as mineralization occurs.  Histologically, there will be irregular trabeculae of woven bone with osteoblasts present (unlike FD).  Treatment is by intraoral excision by enucleation while attempting to preserve teeth and neurovascular structures. 

Recurrence is rare and these lesions have no malignant potential.

Central giant cell granulomas have been known, in the past, as “reparative” granulomas.  However, some feel that “granuloma” is a misnomer  and call it central giant cell lesion instead.  It is a non-neoplastic lesion of fibrous tissue with foci of hemorrhage, multinucleated giant cells and occasional trabeculae of woven bone.  Clinically, young patients are most often affected (75% less then 30).  It can present either aggressively or nonaggressively.  Aggressive lesions are painful and have rapid growth and cortical perforation.  Nonaggressive lesions are more common  and often asymptomatic.  Radiographically they have a multilocular radiolucency with a well demarcated border.  Histologically there is a proliferation of spindled fibroblasts in a collagenous stroma with numerous vascular channels and multinucleated giant cells.  The differential diagnosis should include giant cell tumor, hyperparathyroidism and cherubism.  Treatment involves aggressive curettage with removal of bony margins, while considering more aggressive resection for “aggressive” lesions.  Recurrence occurs 20% of the time and aggressive lesions are more likely to recur. 

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