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    Mandibular Cysts And Odontogenic tumors

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    dr:nana

    Posts : 33
    Join date : 2010-02-26

    Mandibular Cysts And Odontogenic tumors

    Post  dr:nana on Wed Aug 18, 2010 3:44 pm

    Keratinizing and Calcifying Odontogenic Cyst


    The keratinizing and calcifying odontogenic cyst (KCOC), or Gorlin cyst, is not actually a cyst but rather a neoplasm with cystic tendencies. Some KCOC lesions are actually solid. This is a very rare lesion with no age, sex, or location predilections. KCOC may be found anywhere in the jaws, and one fourth of lesions are found in peripheral soft tissue (eg, gingiva). If KCOC is not discovered as an incidental finding on radiographic examination, the earliest clinical presentation usually is a localized swelling.
    These lesions arise from a more mature enamel epithelium than ameloblastoma, and, accordingly, they have less growth potential.
    Radiographic findings
    These are nondescript radiolucencies that may contain flecks of opacity. They may become quite large if not discovered serendipitously.
    Histologic characteristics
    These lesions are lined by an epithelium that is similar in appearance to ameloblastoma (eg, polarized basal layer and SR are present). KCOC appears somewhat similar to the unicystic ameloblastoma, with masses of keratinized squamous epithelial cells within the SR. However, these cells have no nuclei and are called ghost cells. This ghost epithelium eventually herniates into the connective tissue, causing a connective tissue foreign body response that results in dentinoid dystrophic calcification and the formation of granulation tissue. More simply, this lesion represents enamel epithelium that has a tendency to mature but is unable to form enamel. The result is the formation of ghost keratin that may, in turn, induce dentinoid. The similarities between this lesion and the craniopharyngioma have previously been mentioned.
    Treatment
    These lesions are surgically removed and rarely recur after excision.
    Odontogenic Myxoma


    This is a benign infiltrative lesion that is clinically indistinguishable from ameloblastoma. It is found in tooth-bearing areas, and a slight predilection for the mandible exists. It generally appears in the early third to fourth decades of life as a slow-growing expansile lesion. If odontogenic myxoma is left untreated, it is invasive and destructive. It is derived from dental mesenchyme (papilla) or follicle.
    Radiographic findings
    The radiographic appearance of this lesion is not distinctive. It appears quite similar to ameloblastoma (eg, multilocular radiolucency), though some authors believe that the individual loculations are somewhat smaller in odontogenic myxoma (myxofibroma).
    Histologic characteristics
    A few stellate fibroblasts with copious amounts of hyaluronic acid, scant collagen fibrils, and no capsule describe the histologic appearance of this lesion. The hyaluronic acid component stains with Alcian blue, reminding one of the appearance of Wharton jelly. This lesion looks like developing pulp and may be confused with a developing third molar.
    Treatment
    As with ameloblastoma, this lesion is treated with block excision. Recurrences occur although with somewhat less frequency than with ameloblastoma.
    Ameloblastic Fibroma


    Ameloblastic fibroma is a true mixed tumor arising from a combination of 2 embryonic tissues. The epithelial component is able to induce mesenchyme but not to the extent of developing dental hard tissues. It is a relatively uncommon tumor of young people (aged 5-20 y); 75% of ameloblastic fibromas are found in the posterior mandible in the area of a developing tooth. It is benign and expansile, growing as a pushing front rather than invading surrounding tissues.
    Radiographic findings
    This lesion appears as a uniocular or bilocular radiolucency, most often in the posterior mandible. The radiographic appearance is identical to that of unicystic ameloblastoma, and both lesions should be differential diagnoses because they affect similar age groups and have similar clinical and radiographic appearances. Histologic examination differentiates the two.
    Histologic characteristics
    The epithelial component of this lesion is almost identical to that of ameloblastoma; however, the connective tissue component looks like dental pulp. It is a young, cellular, homogenous connective tissue without much dense collagen. The epithelial and connective tissue components grow together inside a capsule.
    Treatment
    The treatment of this lesion is block excision with a border of normal bone. With simple enucleation, recurrence rates of 20-40% have been reported. Sarcomatous change (ameloblastic fibrosarcoma) has also been reported with recurrence or inadequate excision.
    Ameloblastic Fibro-odontoma


    Ameloblastic fibro-odontoma is an extremely rare odontogenic lesion that develops dental hard tissues (eg, dentin, enamel, cementum). It appears most often before age 20 years and has a slight predilection for the premolar area in either jaw. Although these lesions can become quite large, they generally do not have much growth potential.
    Radiographic findings
    Ameloblastic fibro-odontoma appears as a well-demarcated radiolucency with a large central opacity. These lesions almost always are found in association with a tooth. Some similarity exists in radiographic appearance to that of the Pindborg tumor and Gorlin cyst because this is a mixed radiolucent/radiopaque lesion. If located in the anterior mandible, AOT also may be included in the radiographic differential diagnoses.
    Histologic characteristics
    This lesion has the histologic characteristics of ameloblastic fibroma. However, epithelial induction of connective tissue occurs to the point of histodifferentiation, leading to presence of dentin, enamel, and/or cementum in the microscopic presentation.
    Treatment
    Surgical excision of ameloblastic fibro-odontoma is the usual proposed treatment. These lesions do not often recur. The literature contains some support for sarcomatous change with recurrence.
    Complex Odontoma


    Complex odontoma lesions represent further histologic differentiation of the odontogenic pluripotential epithelium. Findings from this lesion resemble those of ameloblastic fibro-odontoma but extended one step further. The epithelium in this lesion has involuted, leaving disorganized dental hard tissues in place. These are common lesions, and they persist throughout life. They are usually detected in adolescence and have a predilection for the mandibular molar regions; however, they can be found in other areas of the jaws.
    Radiographic findings
    These lesions are generally described as sunburst radiopacities surrounded by a thin, uniform, radiolucent rim. Although this description may have some superficial resemblance to the radiographic description of osteosarcoma, the association with a tooth, the clear demarcation of the lesions' borders, and the lack of pain and/or swelling serve to delineate this very benign lesion from osteosarcoma.
    Histologic characteristics
    The histodifferentiation of this lesion is extended one step further than that of ameloblastic fibro-odontoma. In complex odontoma, a physiologic reduction of the ameloblastic epithelium is found. A mixed honeycomb presentation of enamel, cementum, dentin, and pulpal tissue is present. Histodifferentiation but no morphodifferentiation is observed in this lesion.
    Treatment
    Simple removal or radiographic observation is the method of treatment. These lesions do not recur.
    Compound Odontoma


    This is the most common odontogenic tumor. It represents the product of both histodifferentiation and morphodifferentiation of odontogenic tissues, resulting in what appears as a cluster of multiple abortive teeth. It is most commonly found in the maxillary anterior alveolar bone but may be located anywhere within the tooth-bearing segments of the jaws. It is often responsible for preventing normal tooth eruption, thus it is usually discovered during adolescence.
    Radiographic findings
    Multiple tiny toothlike structures are contained within a fine radiolucent rim.
    Histologic characteristics
    Histology of compound odontomas approaches normal tooth structure. Gross clinical examination is usually sufficient for diagnosis.
    Treatment
    Simple removal is the method of treatment. These lesions do not recur.
    Cementoblastoma


    Cementoblastoma, as distinguished from cementoma, is a true neoplasm of cementum. This benign neoplasm is rare and is usually observed in patients younger than 25 years. It is most often found in association with the apex of the mandibular first molars (50% of lesions), and it is never found in association with the anterior dentition. The lesion is usually asymptomatic, although occasionally the associated tooth may be slightly sensitive to percussion.
    Radiographic findings
    A round opaque sunburst mass attached to the apex of a tooth that is well-demarcated and surrounded by a thin radiolucent rim is observed. The lesion obscures the lamina dura. Students sometimes confuse it with condensing osteitis, a common lesion resulting from low-grade periapical irritation that stimulates bone growth. Although the most usual location for the 2 lesions is the same, condensing osteitis does not obscure the periodontal ligament (PDL) space and tends to be more irregular in outline. The mature cementoma, also known as periapical cemental dysplasia, is another common lesion that students may confuse with cementoblastoma. However, cementoma is usually located in the mandibular anterior region and does not obscure the PDL space. Cementomas actually have 3 developmental stages: osteolytic (at which point the lesion appears as a radiolucency), cementoblastic (mixed radiolucent/radiopaque), and mature (radiopaque).
    Histologic characteristics
    Plump cementoblasts separated by cemental partitions form the histology of this encapsulated lesion.
    Treatment
    Removal of attached tooth and tumor is the method of treatment. No recurrences are reported.

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