Tumors And Cysts Of The Dentoalveolar Structures

About 9 percent of all tumors in the oral cavity are odontogenic and may differentiate toward epithelial or the odontogenic ectomesenchymal line and are classified accordingly (Table 2-5). They are predominantly benign with rare exceptions.

Ameloblastoma is a locally aggressive, usually intraosseous tumor of odontogenic epithelium most commonly involving the posterior part of mandible and sometimes the posterior maxilla. The tumor affects both sexes at all ages, with a higher incidence in the third to fifth decades. The tumors are usually multicystic with solid areas (Figure 2-49). Various histologic types are described, the most common being follicular and plexiform. The uncommon uni-cystic variant may be radiologically misinterpreted as an odontogenic cyst. The peripheral ameloblas-

Figure 2-47. A, A neglected basal cell carcinoma of the skin of face. The patient was a 73-year-old woman who had the lesion for many years. The eye is identified in the right side of the photograph. B, Microphotograph shows nests of cellular blue basaloid cells with peripheral pallisading, central small cyst formation and a single keratin pearl. The tumor is connected to the overlying epidermis.

Figure 2-47. A, A neglected basal cell carcinoma of the skin of face. The patient was a 73-year-old woman who had the lesion for many years. The eye is identified in the right side of the photograph. B, Microphotograph shows nests of cellular blue basaloid cells with peripheral pallisading, central small cyst formation and a single keratin pearl. The tumor is connected to the overlying epidermis.

Figure 2-48. Sebaceous carcinoma. The tumor shows sebaceous differentiation with large cells with multiple small vacuoles. The smaller cells with hyperchromatic nuclei can show brisk mitosis. Ker-atinization is identified.

toma is extraosseous, located in the gingiva or buccal mucosa. The unicystic peripheral and desmo-plastic ameloblastoma have lower recurrence rates than the conventional multicystic ameloblastoma. Rare metastasis after prolonged illness punctuated by multiple surgeries and/or radiotherapy is known (malignant ameloblastoma). Odontoameloblastoma is an extremely rare, composite, true neoplasm consisting of an ameloblastoma and hard dental tissue eg, dentine, cementum or enamel. The clinical behavior is similar to ameloblastoma.

The ameloblastic fibroma is essentially a solid intraosseous fibrous lesion with scattered foci of attenuated ameloblastic epithelium. Ameloblastic fibrodentinoma (dentinoma) and fibro-odontoma are similar to ameloblastic fibroma, but the former

Table 2-5. BENIGN TUMORS OF THE ODONTOGENIC TISSUE

Tumors related to Odontogenic Epithelium Ameloblastoma: central and peripheral Squamous odontogenic tumor Clear cell odontogenic tumor Calcifying epithelial odontogenic tumor

Tumors related to Odontogenic Mesenchyme Odontogenic fibroma: central and peripheral Odontogenic myxoma/fibromyxoma Cementifying tumors

Cementoblastoma (cementoma) Cementifying and cemento-ossifying fibroma Mixed Tumors related to Odontogenic Epithelium and Mesenchyme Ameloblastic fibroma Ameloblastic fibrodentinoma Ameloblastic fibro-odontoma Odontoameloblastoma Odontoma: complex and compound Adenomatoid odontogenic tumor Calcifying odontogenic cyst demonstrates additional formation of dentine, and the latter both dentine and enamel. The tumors show variable radio-opacity depending upon the amount of dentine and enamel formation.

Squamous odontogenic tumor is an intraosseous infiltrative tumor composed of islands of well-differentiated squamous cells, sometimes with central cystic change. Most behave in a benign fashion requiring curettage only. The clear cell odontogenic tumor consists of islands of clear epithelial cells. Most tumors are benign though locally aggressive, and clinical behavior appears to be slightly worse than ameloblastoma. Rarely, primary intraosseous squamous cell carcinoma

Figure 2-49. Ameloblastoma. The central cystic portion of the tumor contains a loose reticulum of stellate cells. There is a peripheral layer of tall columnar cells with dark nuclei resembling the inner dental epithelium.

and clear cell adenocarcinoma (odontogenic carcinoma) occur and are believed to arise in intraosseous remnants of the odontogenic epithelium. They may be seen in association with an odontogenic cyst (type 1), ameloblastoma (type 2) or may arise de novo (type 3), and may be keratinizing or non-keratinizing.

The calcifying epithelial odontogenic tumor (Pindborg tumor) presents as a painless slow-growing mass of variable radiolucency, most commonly in the posterior lower jaw, in adults between the ages of 20 to 60 years. It may be associated with an unerupted tooth. One-third of cases may present in the maxilla. Microscopically, the tumor shows sheets of polyhedral, sometimes pleomorphic epithelial and clear cells in a fibrous stroma. Characteristically, large globular masses of acidophilic amyloid-like material and variable degrees of calcification may be seen. The clinical behavior is similar to ameloblastoma. The adenoma-toid odontogenic tumor occurs commonly in the anterior maxilla in the second decade of life. The presence of a capsule, duct-like structures and dentine are characteristic. Enucleation may be adequate treatment. Calcifying odontogenic cyst has a cystic component lined by odontogenic epithelium containing characteristic "ghost" epithelial cells, and a mesenchymal component which may contain dental hard tissue. It usually presents as an intraosseous lesion in the second decade of life and may not be a true neoplasm.

Odontoma is a developmental anomaly occurring in association with the crown of a developing tooth in young individuals. The complex odontoma consists of a disordered mixture of dentine, enamel, cementum and odontogenic epithelium whereas the same components are more orderly with tooth-like formations in the compound odontoma.

Mesenchymal odontogenic tumors are usually tumors of young people affecting the mandible. The odontogenic fibroma may be intraosseous (central) or in the gingiva (peripheral) and contains odonto-genic epithelium. Myxoma is locally destructive and extends through the bone into the soft tissue, making complete surgical resection difficult. Cementoblas-toma (cementoma) consists of large fusing globules and masses of cementum associated with the root of a tooth. A special variant, the gigantiform cemen-toma is a bilateral deposition of cementum in both jaws of young black women with an autosomal dominant inheritance pattern.

Most cysts of the jaw are not true neoplasms. They may arise in the odontogenic epithelium or in developmental fissures. A diagrammatic representation of the different odontogenic cysts is depicted in Figure 2-50.

The most common cyst is the periapical or radicular cyst, an incidental radiologic discovery. The cyst is usually less than 1 cm in size with stratified squamous lining associated with inflammation.

The dentigerous cyst is a destructive cyst associated with the crown of an unerupted and displaced permanent tooth (Figure 2-51). Rarely, neoplastic transformation to ameloblastoma can occur.

Odontogenic keratocyst is another destructive uni- or multiloculated cystic lesion in the posterior mandible and maxilla (Figure 2-52). These cysts

Figure 2-50. Schematic diagram of odontogenic cysts by location.
Figure 2-51. Dentigerous cyst. The cyst is lined by stratified squamous epithelium with an admixture of mucus-secreting cells. The lumen contains hemorrhagic debris showing cholesterol clefts.

have a high propensity for destructive growth and recurrence. They may be associated with the nevoid basal cell carcinoma syndrome, an autosomal dominant condition with high penetrance described by Gorlin and Goltz.59 Other components of the syndrome include skeletal abnormalities, ectopic calcification and dyskeratotic pitting of the hands and feet.

Fissural or developmental cysts are believed to arise in the epithelium entrapped between the bony parts of the jaw bones during embryologic development. The different types are depicted in the diagram (Figure 2-53). The most common is the midline nasopalatine cyst which may be within the bone or in the soft tissue. The lateral nasolabial cyst is also a soft-tissue cyst. The other types of cysts are intraosseous.

Figure 2-52. Odontogenic keratocyst. The cyst is lined by stratified squamous cells showing kera-tinization toward the surface.

Nasolabial

Globulomaxillary

Globulomaxillary

Nasolabial

Nasopalatine

Median palatal

Figure 2-53. Schematic diagram of the fissural cysts.

Nasopalatine

Median palatal

Figure 2-53. Schematic diagram of the fissural cysts.

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  • dora
    Is the mandible part of dentoalveolar structures?
    10 months ago

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