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 Table of Contents  
Year : 2014  |  Volume : 26  |  Issue : 2  |  Page : 178-181

Plexiform variety of unicystic ameloblastoma mimicking an odontogenic keratocyst: A case report

1 Department of Oral Medicine and Radiology, CSMSS Dental College and Hospital, Aurangabad, Maharashtra, India
2 Department of Oral Medicine and Radiology, Bharati Vidyapeeth Dental College and Hospital, Pune, Maharashtra, India

Date of Submission10-Jun-2014
Date of Acceptance30-Sep-2014
Date of Web Publication30-Oct-2014

Correspondence Address:
Ashwini Sudhakar Jadhav
23 Kastur Kunj, Sharada Colony, Beside Dewang Hostel, Pimple Nilakh, Pune - 411 027, Maharashtra
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0972-1363.143695

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Ameloblastoma is the most common clinically significant odontogenic tumor. Its relative frequency equals the combined frequency of all other tumors. Ameloblastoma is one of the most significant odontogenic tumors because of its incidence and clinical behavior. Unicystic ameloblastoma refers to those cystic lesions that show clinical, radiographical or gross features of a mandibular cyst, but on histological examination show a typical ameloblastomatous epithelium lining of the cyst cavity, with or without luminal and/or mural tumor growth. We present a case of unicystic ameloblastoma in a 25-year male patient, with its management.

Keywords: Adamantinoma, ameloblastoma, unicystic, unilocular

How to cite this article:
Jadhav AS, Marathe SP, Patil SP. Plexiform variety of unicystic ameloblastoma mimicking an odontogenic keratocyst: A case report . J Indian Acad Oral Med Radiol 2014;26:178-81

How to cite this URL:
Jadhav AS, Marathe SP, Patil SP. Plexiform variety of unicystic ameloblastoma mimicking an odontogenic keratocyst: A case report . J Indian Acad Oral Med Radiol [serial online] 2014 [cited 2020 Dec 3];26:178-81. Available from: https://www.jiaomr.in/text.asp?2014/26/2/178/143695

   Introduction Top

Ameloblastoma is a true neoplasm of the enamel organ-type tissue, which does not undergo differentiation to the point of enamel formation. The term 'Adamantinoma' was coined by Malassez in 1885. Later, the term 'ameloblastoma' was applied to this particular tumor by Churchill in 1934. [1] It is a slow-growing tumor, locally aggressive, capable of causing facial deformity. The third and fourth decades of life show a peak incidence, with an equal gender distribution. It is often associated with an unerupted third molar. [2] Sometimes it is detected during routine radiographic examination. Ameloblastomas may occur centrally within the bone or peripherally, without an intraosseous component involving the soft tissue overlying the alveolar ridge. The intraosseous variety is of two types: Solid/conventional/multicystic and unicystic. The growth pattern of the unicystic ameloblastoma is seen in approximately 6% of all ameloblastomas. It tends to occur in the younger population.

   Case Report Top

A 25-year-old male reported to the Department of Oral Medicine and Radiology, with a complaint of a slow-growing swelling in the lower left posterior region of the jaw, since three years. There was a past history of trauma to the upper and lower anterior teeth seven years back, following which a small, peanut-sized, intraoral swelling of sudden onset developed in the lower left posterior region of the jaw. The patient consulted a local dentist, who performed fine needle aspiration cytology (FNAC) of the lesion, which suggested a keratocyst. At the time of reporting to us, he was suffering from dull aching and intermittent type of pain in the lower anterior region of the jaw, since five months. Along with it, there was the presence of a large, painless swelling involving the mandibular anterior and posterior regions of the jaw. Physical examination revealed the presence of a single, large, diffuse extraoral swelling in the left parasymphysis region, which was nontender and the temperature of the overlying skin was normal. On clinical examination a single, well-defined, intraoral swelling was noted on the left side of the mandible involving the body of the mandible and the anterior ramus [Figure 1]. It was nontender, with vestibular obliteration, and pitting was positive. The overlying mucosa was normal. Clinical findings were suggestive of an odontogenic keratocyst of the mandible. Aspiration cytology was performed, which yielded a thick, yellowish, cheesy material. A true mandibular occlusal radiograph showed cortical expansion with interspersed septae. The orthopantomograph (OPG) revealed a large cystic lesion extending from the mesial aspect of 38 to the mesial aspect of 42, with deflection and resorption of the roots [Figure 2]. A computed tomographic (CT) scan showed that the cystic lesion was confined to the mandible and had caused decortications bucally. Septum formation within the lesion was noted [Figure 3] and [Figure 4]. Based on the correlation with the clinical and radiographic findings, a final diagnosis of ameloblastoma was made. Before undergoing surgery, routine hematological investigations were performed, which were within the normal limits. The patient was operated under general anesthesia. Considering the extent of involvement of the lesion, hemimandibulectomy followed by fibula grafting was planned and performed. The resected specimen [Figure 5] showed epithelial proliferation in the form of anastomosing cords and islands. Reversal of polarity with hyperchromatism was observed in the basal cells. The underlying stroma revealed loose bundles of collagen fibers with areas of myxoid and cystic degeneration [Figure 6]. The histological picture was suggestive of a plexiform variety of unicystic ameloblastoma. The patient was then followed up for two months without any evidence of recurrence [Figure 7].
Figure 1: Facial view showing extraoral swelling over the left mandible

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Figure 2: Cropped OPG showing a large unilocular cystic lesion crossing the midline

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Figure 3: Sagittal section (CT) showing decortication of the buccal cortical plate

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Figure 4: 3-D reconstruction (CT) with interspersed septa

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Figure 5: Resected mandible section

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Figure 6: Photomicrograph showing intramural nodules with islands of infiltrating ameloblastomatous tissue

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Figure 7: Postoperative picture after two months, with normal mouth opening

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   Discussion Top

Unicystic ameloblastoma (UA) accounts for 10-15% of all extraosseous ameloblastomas, according to various studies. Whether unicystic ameloblastoma originates de novo as a neoplasm or whether it is a result of neoplastic transformation of the non-neoplastic cyst epithelium has long been debated. Both mechanisms probably occur, but the proof, which is involved in an 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. This was consistent with our patient too, who was aged 25 years. More than 90% of UAs 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. In our case, the patient is a male, with involvement of the mandibular posterior region. Few of the UAs are associated with an impacted tooth (dentigerous type), but this is not true in our case (non-dentigerous type).

The radiographic appearance is peculiar, with a circumscribed radiolucency in association with the crown of a tooth. It appears as a single cyst-like, unilocular radiolucency in the mandibular posterior region, with smooth, well-defined borders, as was present in our case. However, it may also appear as a multilocular radiolucency. The unilocular variant has an average age of onset of 22 years and the multilocular type, 33 years. The mural variety is associated with pericoronal radiolucency around the tooth with a hyperostotic rim surrounding it.

The differential diagnoses pertaining to the present case include central giant-cell granuloma, odontogenic keratocyst, and traumatic bone cyst. Central giant-cell granuloma lesions are merely found anterior to the molar and have a female predilection. Odontogenic keratocysts are associated with the mandibular third molar area and ascend upward to involve the ramus and coronoid process of the mandible. It does not cause cortical expansion, as has been seen in this case. Traumatic bone cysts have a history of prior trauma to the region, with a well-corticated radiolucency of not more than 3 cm in diameter.

Microscopically, there should be a single cystic sac lined by ameloblastomatous epithelium, mostly in the focal areas, for diagnosing a lesion as a UA. Owing to the high recurrence rate of UA, it should be differentiated from odontogenic cysts. [3] Ackermann, [4] in a clinicopathological study of 57 cases of unicystic ameloblastomas, described the following classifications based on the histological features:

Group I: Luminal UA (tumor confined to the luminal surface of the cyst)

Group II: Intraluminal/plexiform UA (nodular proliferation into the lumen without infiltration of the tumor cells into the connective tissue wall)

Group III: Mural UA (invasive islands of ameloblastomatous epithelium in the connective tissue wall not involving the entire epithelium).

Philipsen and Reichart [5] have suggested another histological subgrouping, which is as follows:

Subgroup 1: Luminal UA

Subgroup 1.2: Luminal and intraluminal

Subgroup 1.2.3: Luminal, intraluminal, and intramural

Subgroup 1.3: Luminal and intramural

The UAs under subgroups 1 and 1.2 can be treated conservatively (with careful enucleation), whereas, those under subgroups 1.2.3 and 1.3, showing intramural growths, require radical resection, similar to a solid or multicystic ameloblastoma. [5] As the foci of the ameloblastoma may embed deeply into the bone during vigorous curettage, it must be avoided after enucleation. Subgroups 1 and 1.2 UAs can be treated with Carnoy's solution (chemical cauterization). As the cystic wall in UAs in subgroups 1.2.3 and 1.3 have islands of ameloblastomatous tumor cells, which may have penetrated into the surrounding cancellous bone, there is a high risk of recurrence, and hence, require more aggressive surgical procedures. [6],[7],[8],[9] The average recurrence period for UAs is seven years. The recurrence rate differs with the histological subtypes of UA, with 35.7% recurrence seen in UAs showing invasion of the fibrous wall and the other types showing a recurrence rate of only 6.7%. [9] The type of initial treatment also decides the recurrence rate. According to Lau et al., [10] there is a recurrence rate of 3.6% for resection, 30.5% for enucleation alone, 16% for enucleation followed by Carnoy's solution application, and 18% for marsupialization followed by enucleation.

As in our case, the lesion was very extensive and had crossed the midline, irrespective of its histopathological variety, the management plan was modified. Whether the lesion is of type I or II, it is always better to manage a case with conservative treatment.

   Acknowledgments Top

The authors would like to acknowledge the valuable guidance and help from the Department of Oral and Maxillofacial Surgery, Bharati Vidyapeeth Dental College and Hospital, Pune, and Department of Oral Pathology, Bharati Vidyapeeth Dental College and Hospital, Pune.

   References Top

Kahn MA. Ameloblastoma in young persons: A clinicopathologic analysis and etiologic investigation. Oral Surg Oral Med Oral Pathol 1989;67:706-15.  Back to cited text no. 1
Gerzenshtein J, Zhang F, Caplan J, Anand V, Lineaweaver W. Immediate mandibular reconstruction with microsurgical fibula flap transfer following wide resection for ameloblastoma. J Craniofac Surg 2006;17:178-82.  Back to cited text no. 2
Konouchi H, Asaumi J, Yanagi Y, Hisatomi M, Kawai N, Matsuzaki H, et al. Usefulness of contrast enhanced-MRI in the diagnosis of unicystic ameloblastoma. Oral Oncol 2006;42:481-6.  Back to cited text no. 3
Philipsen HP, Reichart PA. Classification of odontogenic tumors and allied lesions. In: Philipsen HP, Reichart PA, editors. Odontogenic tumors and allied lesions. London: QuintessencePub Co Ltd; 2004. p. 21-3.  Back to cited text no. 4
Philipsen HP, Reichart PA. Unicystic ameloblastoma. In: Philipsen HP, Reichart PA, editors. Odontogenic tumors and allied lesions. London: Quintessence Pub Co Ltd; 2004. p. 77-86.  Back to cited text no. 5
Chana JS, Chang YM, Wei FC, Shen YF, Chan CP, Lin HN, et al. Segmental mandibulectomy and immediate free fibula osteoseptocutaneous flap reconstruction with endosteal implants: An ideal treatment method for mandibular ameloblastoma. Plast Reconstr Surg 2004;113:80-7.  Back to cited text no. 6
Li TJ, Kitano M, Arimura K, Sugihara K. Recurrence of unicystic ameloblastoma: A case report and review of the literature. Arch Pathol Lab Med 1998;122:371-4.  Back to cited text no. 7
Li TJ, Browne RM, Matthews JB. Expression of proliferating cell nuclear antigen (PCNA) and Ki-67 in unicystic ameloblastoma. Histopathology 1995;26:219-28.  Back to cited text no. 8
Li T, Wu Y, Yu S, Yu G. Clinicopathological features of unicystic ameloblastoma with special reference to its recurrence. Zhonghua Kou Qiang Yi Xue Za Zhi 2002;37:210-2.  Back to cited text no. 9
Lau SL, Samman N. Recurrence related to treatment modalities of unicystic ameloblastoma: A systematic review. Int J Oral Maxillofac Surg 2006;35:681-90.  Back to cited text no. 10


  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]


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