Year : 2007 | Volume
: 25 | Issue : 2 | Page : 106--110
Unicystic ameloblastoma of the maxilla: A case report
VJ Paikkatt, S Sreedharan, VP Kannan
Department of Pedodontics, Govt. Dental College, Kozhikode, Kerala, India
Dept. of Pedodontics, Govt. Dental College, Kozhikode, Kerala
Unicystic ameloblastoma is believed to be less aggressive and responds more favorably to conservative surgery than the solid or multicystic ameloblastomas. This report is a rare case of unicystic ameloblastoma of the maxilla that was treated by enucleation under suspicion of a radicular cyst related to a dens in dente. The neoplastic nature of the lesion became evident only when the enucleated material was available for histologic examination. With this report, the authors illustrate the importance and complexity of a differential diagnosis of lesions with a cystic aspect in the anterior region of the maxilla, among them - inflammatory radicular cysts, odontogenic keratocysts, adenomatoid odontogenic and unicystic ameloblastoma. Relevant diagnostic problems and choice of treatment of unicystic ameloblastoma are presented along with a review of the literature.
|How to cite this article:|
Paikkatt V J, Sreedharan S, Kannan V P. Unicystic ameloblastoma of the maxilla: A case report.J Indian Soc Pedod Prev Dent 2007;25:106-110
|How to cite this URL:|
Paikkatt V J, Sreedharan S, Kannan V P. Unicystic ameloblastoma of the maxilla: A case report. J Indian Soc Pedod Prev Dent [serial online] 2007 [cited 2021 Jul 28 ];25:106-110
Available from: https://www.jisppd.com/text.asp?2007/25/2/106/33459
Ameloblastomas are benign tumors whose importance lies in its potential to grow to enormous size with resulting bone deformity. Ameloblastomas originate from the epithelium involved with the formation of teeth: enamel organ, odontogenic rests of Malassez, reduced enamel epithelium and odontogenic cyst lining. Ameloblastomas are usually asymptomatic and found on routine dental radiographs; however, they may also present with jaw expansion. Radiographically, ameloblastomas can either be uni or multilocular with well-circumscribed margins. Its slow but relentless growth may cause movement of tooth roots or root resorption. Ameloblastomas are typically differentiated histologically into unicystic intraosseous, multicystic, solid intraosseous (80-90% of all ameloblastomas) or peripheral. The term unicystic ameloblastoma refers to those cystic lesions that show clinical, radiographic or gross features of a jaw cyst but on histologic examination show a typical ameloblastomatous epithelium lining part of the cyst cavity, with or without luminal and/or mural tumor growth. The unicystic ameloblastoma is a less encountered variant of the ameloblastoma. It appears more frequently in the second or third decade with no sexual or racial predilection. It is almost exclusively encountered asymptomatically in the posterior mandible. Treatment for ameloblastomas ranges from en bloc excision to curettage, depending on histology and clinical presentation of the tumor. The report is a rare case of unicystic ameloblastoma of the maxilla in an 11-year-old female.
An 11-year-old girl was referred to the Department of Pedodontics, Govt. Dental College, Kozhikode, Kerala, with a swelling on the right side of the cheek. Present history revealed that the swelling was slowly growing over a period of 2 months and was not associated with pain, tenderness or discharge. However, she had a distorted middle third of the face due to increased size of swelling, extending diffusely from right ala of nose to the right temporal region [Figure 1]. Intraoral examination showed a swelling on the buccal aspect, extending from upper lateral incisor to second premolar, obliterating labial sulcus and palatally extending from midline to distal of second premolar [Figure 2],[Figure 3]. On palpation, the swelling was bony hard, with slight softness on palatal side of 14 and 15 with fluctuance [Figure 3]. Past history and medical history were unremarkable. She was taking no medication and had no history of known drug allergy. Her physical examination revealed no abnormality other than those related to the chief complaint. CT scan report suggested a developmental cyst [Figure 4],[Figure 5]. The IOPA and occlusal view showed a well-defined radiolucency extending from distal of 11 to distal of 15 that appeared to be associated with dens in dente in relation to 12 with open apex [Figure 6],[Figure 7]. On aspiration from area of fluctuance, a yellow straw-colored fluid was obtained and provisional diagnosis of periapical cyst was made. Enucleation of the lesion was performed to completely extirpate the cystic lesion with extraction of 12 [Figure 8],[Figure 9],[Figure 10]. The specimen had size of 4.5 cm 3 dimensions lxbxw [Figure 10]. Surprisingly, the subsequent histopathologic diagnosis was a simple unicystic ameloblastoma [Figure 11]. Histologically, the cyst was lined by ameloblastic epithelium with tall columnar basal layer, subnuclear vacuoles, reverse nuclear polarity and thin layer of edematous, degenerate-appearing stellate cells. The immediate postoperative healing was uneventful.
Unicystic ameloblastoma, a variant of ameloblastoma first described by Robinson and Martinez  in 1977, refers to those cystic lesions that show clinical and radiologic characteristics of an odontogenic cyst but in histologic examination show a typical ameloblastomatous epithelium lining part of the cyst cavity, with or without luminal and/or mural tumor proliferation. This variant is believed to be less aggressive, tends to affect patients at a younger age and its response to enucleation or curettage is more favorable than the classic solid or multicystic ameloblastomas. Based on the character and extent of tumor cell proliferation within the cyst wall, several histologic subtypes of unicystic ameloblastoma are recognized, which include those of simple cystic nature, those with intraluminal proliferative nodules and those containing infiltrative tumor islands in the cyst walls. While the first two groups of lesions may be treated successfully by enucleation or curettage, it has been suggested that recurrence following conservative surgery is more likely to occur in the third group and that these lesions should therefore be treated in the same manner as solid ameloblastomas. 
Unicystic ameloblastoma requires separate consideration based on clinical, radiographic and pathologic features and its response to treatment.
Unicystic ameloblastoma accounts for 10-15% of all extraosseous ameloblastomas in various studies. Whether unicystic ameloblastoma originates de novo as a neoplasm or whether it is a result of neoplastic transformation of non-neoplastic cyst epithelium has long been debated. Both mechanisms probably occur, but proof, which is involved in individual patient, is virtually impossible to obtain.
Unicystic ameloblastomas are most often seen in young patients, with about 50% of such tumors diagnosed during the second decade of life. More than 90% of unicystic ameloblastomas are found in the mandible, usually in the posterior region. The lesion is often asymptomatic, although a large lesion may cause painless swelling of the jaws.
Three histopathologic variants of unicystic ameloblastoma have been described.  In the first type (luminal unicystic ameloblastoma), the tumor is confined to luminal surface of cyst; while the lesion consists of fibrous cyst wall, with a lining that consists partially or totally of ameloblastic epithelium. This demonstrates a basal layer of columnar or cuboidal cells with hyperchromatic nuclei that show reverse polarity and basilar cytoplasmic vacuolization. The overlying epithelial cells are loosely cohesive and resemble stellate reticulum. The finding thus seems to be related to inflammatory edema.
In the second microscopic variant (intraluminal unicystic ameloblastoma), one or more nodules of ameloblastoma project from cystic lining into lumen of cyst. These nodules may be relatively small or they largely fill the cystic lumen. In some cases, nodules of tumor that project into lumen demonstrates an edematous plexiform pattern that resembles plexiform pattern seen in conventional ameloblastoma. These lesions are referred to as plexiform unicystic ameloblastoma.
In the third variant (mural unicystic ameloblastoma), the fibrous wall of cyst is infiltrated by typical follicular or plexiform ameloblastoma. The extent and depth of ameloblastic proliferation may vary considerably. With any presumed unicystic ameloblastoma, multiple sections through many levels of specimen are necessary to rule out the possibility of mural invasion of tumor cell.
The clinical and radiographic findings in most cases of unicystic ameloblastoma suggest that the lesion is an odontogenic cyst. These lesions are usually treated by enucleation. The diagnosis of ameloblastoma is made only after microscopic examination of presumed cyst. If the ameloblastic elements are confined to the lumen of the cyst, with or without intraluminal tumor extension, then cyst enucleation is the treatment. The patient however should be kept under long-term follow-up.
If specimens show extension of tumor into fibrous cyst wall for any appreciable distance, subsequent management is more controversial. Some surgeons believe that local resection of area is indicated as a prophylactic measure, while others prefer to keep the patient under radiographic observation and delay further treatment until there is evidence of recurrence. Recurrence rate of 10-20% has been reported after enucleation and curettage of unicystic ameloblastoma. This is considerably less than 50-90% recurrence rate noted after curettage of conventional solid and multicystic extraosseous ameloblastoma. ,,,
The probable reason for a bad prognosis is that the unicystic ameloblastoma is generally cystic, well localized and surrounded by a fibrous capsule. However, once the tumor has broached the periphery of the capsule, it can infiltrate the surrounding cancellous bone and therefore may behave more aggressively. Preoperative diagnosis of unicystic ameloblastoma can be difficult or sometimes impossible. This variant of ameloblastoma shows considerable similarities with dentigerous cysts, both clinically and radiographically and some authors have raised the possibility of its origin from a preexisting dentigerous cyst. Furthermore, the epithelial lining of a unicystic ameloblastoma is not always uniformly characteristic and is often lined partly by a nonspecific thin epithelium that mimics the dentigerous cyst lining.  The true nature of the lesion may only become evident when the entire specimen is available for histologic examination. The age of the patient is another influencing factor related to the choice of treatment. As unicystic ameloblastoma tends to affect young adolescent patients, the concern to minimize surgical trauma and permit jaw function and tooth development to proceed reasonably unimpaired should be one of the important aspects in tumor management. To obliviate the problem of deformity, a simple enucleation was performed to remove the whole lesion after the completion of the tooth eruption in this region.
While conservative surgery seems to have been justified in preference to mutilating radical surgery for this young patients, choice of treatment has to be considered in conjunction with other clinical and pathologic factors such as the size, location and growth pattern of the tumor. Whatever surgical approach the surgeon decides to take, long-term follow-up is mandatory, as recurrence of unicystic ameloblastoma may be long delayed. 
The diagnosis of unicystic ameloblastoma was based on clinical, histopathologic and CT features. Unicystic ameloblastoma is a tumor with a strong propensity for recurrence, especially when the ameloblastic focus penetrates the adjacent tissue from the wall of the cyst. The ability to predict this potential occurrence prior to surgery would greatly enhance therapeutic strategies for reducing the incidence. It should be emphasized that despite a clinical diagnosis of periapical disease of endodontic origin, a nonendodontic lesion may be present, as was evident in this case.
Dept. of Oral Pathology, Govt. Dental College, Kozhikode Patient's parents for their consent to present the article for publication.
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