COM August 2005 Diagnosis

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Odontogenic keratocyst (OKC) is an aggressive odontogenic cyst, known for its rapid growth ad its tendency to invade the adjacent tissues, including bone. It has a high recurrence rate and is associated with basal cell nevus syndrome. It affects patients in the age ranges of 20-29 and 40-59, but cases in patients ranging in age from 5 to 80 years have been reported (1). The distribution between sexes varies from equal distribution to a male-to-female ratio of 1.6:1, except in children. Odontogenic keratocysts may occur in any part of the upper and lower jaw, with the majority (almost 70%) occurring in the mandible. They occur most commonly in the angle of the mandible and ramus (2). Radiographically, OKCs present predominantly as unilocular radiolucencies with well-defined or sclerotic borders; they may also present as multilocular radiolucencies, but rarely. OKCs commonly present as unilocular radiolucency with scalloped borders. Teeth associated with OKC are vital. OKCs grow to sizes larger than any other odontogenic cysts. They usually penetrate the bone rather than expand it and grow in an anterior to posterior direction (1-2). Despite this aggressive growth, they often remain asymptomatic, thus growing to large sizes and hollowing the bone. The radiographic and clinical findings of this case are strongly supportive of an OKC. The histology however is not OKC.

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Traumatic bone cyst is best called traumatic bone cavity since this condition does not represent a true cyst. Traumatic bone cavity is not unique to the jawbones; it is also described in the long bones and is known as a simple solitary bone cyst occurring mostly in the humerus or femur, close to the epiphyseal plate (3). For more information, please read case of the month June 2004. Some reports suggest that it is more common in males (4) while others report equal distribution between males and females (3). The long bone counterpart is more common in males by a ratio of 2.5:1. Most reports agree that the average age of occurrence is below 20 years of age (3-4). The mandible is the most commonly affected area, where over 95% of the cases occur, especially in the posterior premolar-molar area. They rarely extend to the ramus and are known to cross the midline anteriorly. In one study, 27% were anterior to the canine and some crossed the midline. They are usually unilocular and radiolucent, typically above the alveolar canal and in many cases with a scalloped superior border spreading between the roots of teeth. The latter are vital and are frequently found hanging within the empty cavity. About 25% of the lesions present in the anterior mandible apical to the canine tooth and usually are round and unilocular, which can be mistaken for a periapical lesion leading to an unnecessary endondontic treatment. This case is in the posterior mandible but is not scalloped and for that reason traumatic bone cavity was considered but with caution. Clinically, surgeons almost always report an empty cavity at entrance; occasionally straw-colored fluid is described to be present. Blood clot is also present occasionally. The bony cavity is scraped to generate bleeding, which is considered the treatment of choice for this condition. Other reports demonstrate healing of traumatic bone cavity after injection of autogenous blood, after aspiration and after endodontic treatment. These lesions may spontaneously heal, but rarely. The clinical finding of a solid tumor and the histology are not supportive of traumatic bone cavity.

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Central ossifying fibroma (COF) is a benign neoplasm of bone origin that presents as a well-demarcated to corticated complete radiolucency to a mixed radiolucent/radiopaque mass with a peripheral radiolucent rim (6). It is a slow-growing, expansile lesion with characteristic downward expansion of the inferior border of the mandible. It can also expand buccally and lingually. The associated teeth are vital. It is common in young adults around 35 years of age and is five times more likely to occur in females than males. It affects the posterior mandible in about 90% of cases. The age of the patient, the location and the radiographic findings can be consistent with the early (radiolucent) stage of a COF. The histology however is not supportive of this entity.

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Ameloblastoma is one of the most common benign neoplasms of odontogenic origin. It accounts for 11% of all odontogenic neoplasms/hamartomas (7-8). It is a slow-growing, persistent, and locally aggressive neoplasm of epithelial origin. It affects a wide range of age distribution but is mostly a disease of adults, at an average age of 33, with equal sex distribution. Reports from Africa and India show a male predilection; it also has a predilection for occurrence in black patients (9). The location and age of this patient can be consistent with an ameloblastoma. The unilocular radiolucency is unusual for the solid type but is consistent with the 10% of the unicystic ameloblastomas that occur in an extra-follicular manner. About 85% of ameloblastomas occur in the posterior mandible; most of these occur in the molar-ramus area, and some occur in the anterior mandible. Three types are described (for details please read the Clinical Case Discussion in October 2004issue of E-PIE). Solid ameloblastoma is characteristically expansile, radiolucent and multilocular and not consistent with this case. The unicystic type is radiographically unilocular but in 90% of the time is associated with the crown of an impacted tooth (7-9). The other 10% are not and can present between teeth as is the case here and for that reason, it should be considered on the differential diagnosis. Ameloblastoma, if not treated, can reach very large sizes, causing facial disfigurement. It loosens, displaces and resorbs adjacent teeth. Ameloblastomas are usually not painful unless infected, in which case it can be mildly painful. Parasthesia and anesthesia are extremely rare, unless the lesion is very large in size. Also, ameloblastoma tends to expand rather than perforate the cortical bone; if the latter occurs with extension into the adjacent soft tissue, it has a higher tendency for recurrence and therefore a worse prognosis than cases in which the ameloblastoma is completely encased by bone (7-9). The solid type is treated with en bloc or resection with clean margins. Curettage is the treatment of choice for the unicystic type. The histology of this case is not supportive of ameloblastoma.

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Adenomatoid odontogenic tumor (AOT) is a rare neoplasm (hamartomas) accounting for less than 3% of all odontogenic tumors. It is benign and slow-growing believed to originate from the remnants of the dental lamina or enamel organ. It was first described by Dreibladt, in 1907, as a pseudoadenoameloblastoma (10). In 1969, Philipsen et al proposed the name adenomatoid odontogenic tumor which was later adopted by the World Health Organization with the understanding that this lesion has a benign and non- aggressive behavior (11). It present either within bone (intra-osseous) in 97.2% of the time or on the gingiva (extra-osseous, also known as peripheral) in 2.8% of the time (12). The intra-osseous is further divided into follicular (most common) and extra-follicular (12). The follicular accounts for 73% of all the AOT cases and is associated with the crown of an unerupted/impacted tooth sharing the same radiographic features with a dentigerous cyst (10-13). It is unilocular, corticated radiolucency around the crown and at times goes beyond the crown to involve the root of the tooth. The second type constitutes about 24% of the cases presenting between teeth, apical or away from teeth known as extra-follicular (12-13). This type presents as a unilocular corticated radiolucency often mistaken for an odontogenic keratocyst, lateral periodontal, residual or periapical cysts (14-15). Our case would be classified as extra-follicular AOT (12). The peripheral variant presents on the gingiva mimicking a reactive gingival swelling (14). Anterior maxilla and mandible are the most common locations for AOT with maxilla being 2:1 especially the maxillary canines accounting for 40% of the cases. It has also been described in the posterior mandible and maxilla but less commonly (10, 12). Also, it is rarely described in deciduous teeth. It is more common in females (2:1) between the ages of 10-19 with almost 70% occurring in the second decade. Sizes are usually small around 1-3 cm in diameter, occasionally however large lesions are described (10). Radiographically, it is usually unilocular and radiolucent with clearly defined to corticated margins (10-13). About 10% demonstrate some degree of calcification. OT is usually an asymptomatic lesion with the exception of mild expansion. The extra-follicular type may cause mild displacement of teeth which is the case in our patient. Root resorption is rarely described. Histologically, it is made up of epithelial cells arranged in two patterns, some are spindle-shaped arranged in whorls, nests and bundles and others are cuboidal and arranged in duct-like structures. This lesion is supported a by thick fibrous connective tissue capsule. Sometimes globules of a homogenous material are described which may represent amyloid. The treatment of choice is conservative removal through simple curettage or enucleation. The thick connective tissue capsule makes separation of the lesion from the tooth and surrounding connective tissue easy allowing the clinician to save the tooth Recurrence has been described but is exceedingly rare (10-13).

Treatment

The procedure was performed under local anesthesia. A full flap incision was made from the anterior mandible and posteriorly to the third molar area in order to expose the entire buccal bone. A thin shell of buccal bone was present overlying the buccally expanded lesion (Fig 2). The buccal bone was partially removed enough to expose the lesion. The tumor was solid and well-circumscribed (Fig 3) and was easily enucleated (Fig 3a). The surgical site was thoroughly irrigated and closed. Two week post operative visit demonstrated a well healing surgical site and residual Parasthesia.

Figure 2. This is an intra-oral photograph demonstrating a full-flap surgical procedure exposing the expanded buccal bone with obliteration of the vestibule.

Figure 3. This is an intra-oral radiograph demonstrating the surgical site with partial enucleation of the fully circumscribed tumor protruding from the bony cavity.

Figure 3a. This is the gross appearance of the enucleated lesion. It is round and fully encapsulated.

References

1. Shear M. Odontogenic keratocysts: natural history and immunohistochemistry. Oral Maxillofacial Surg Clin N Am. 2003; 15: 347-362.
2. Oda D, Rivera V et al. Odontogenic keratocyst: the northwestern USA experience. J Contemp Dent Pract. 2000 Feb 15; 1: 60-74.
3. Stoelinga, PJW. Excision of the overlying, attached mucosa, in conjunction with cyst enucleation and treatment of the bony defect with carnoy solution. Oral Maxillofacial Surg Clin N Am. 2003; 15: 407-414.
4. Kaugars GE, Cale AE. Traumatic bone cyst. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1987; 63: 318-324.
5. Dellinger TM, Holder R et al. Alternative treatments for a traumatic bone cyst: a longitudinal case report. Quintessence Int. 1998; 29: 497-502
6. Su L, Weathers DR, et al. Distinguishing features of focal cemento-osseous dysplasia and cemento-ossifying fibromas: II. A clinical and radiologic spectrum of 316 cases. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1997 Nov; 84: 540-549.
7. Reichart PA, Philipsen HP, Sonner S. Ameloblastoma: biological profile of 3677 cases. Eur J Cancer B Oral Oncol 1995;31B:86–99.
8. Gardner DG. Some current concepts on the pathology of ameloblastomas. J Oral Maxillofac Surg 1996;82:660-669.Omandi BI, Guthua SW, Awange DO et al. Maxillary obturator prosthesis rehabilitation following maxillectomy for ameloblastoma: case series of five patients. Int J Prosthodont. 2004;17:464-468.
9. Batra P, Prasad S et al. Adenomatoid odontogenic tumour: review and case report. J Can Dent Assoc. 2005; 71:250-253.
10. Philipsen HP, Birn H. The adenomatoid odontogenic tumor, ameloblastic adenomatoid tumor or adeno-ameloblastoma. Acta Pathol Microbiol Scand 1969; 75:375–398.
11. Philipsen HP, Reichart PA, Zhang KH, Nikai H, Yu QX. Adenomatoid odontogenic tumor: biologic profile based on 499 cases. J Oral Pathol Med 1991; 20:149–158.
12. Sato D, Matsuzaka K et al. Adenomatoid odontogenic tumor arising from the mandibular molar region: a case report and review of the literature. Bull Tokyo Dent Coll. 2004; 45:223-227.