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Year : 2020  |  Volume : 11  |  Issue : 4  |  Page : 220-223

Unicystic ameloblastoma: An unusual case report

Department of Oral Pathology, Microbiology and Forensic Odontology, SRM Dental College, Chennai, Tamil Nadu, India

Date of Submission17-Nov-2020
Date of Acceptance12-Dec-2020
Date of Web Publication05-Feb-2021

Correspondence Address:
Dr. Ramya Mahalingam
Department of Oral Pathology, Microbiology and Forensic Odontology, SRM Dental College, Bharathi Salai, Ramapuram, Chennai - 600 089, Tamil Nadu
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DOI: 10.4103/srmjrds.srmjrds_117_20

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Ameloblastomas are the second most common tumor that originates from the odontogenic epithelium. The common age of occurrence is usually the third decade of life, with majority of the cases involving the mandible. Unicystic ameloblastoma accounts for about 5%–15% of all ameloblastic lesions with no tendency to metastasize. It is a slow-growing tumor but locally invasive with high rate of recurrence, especially the mural variant. We report a case of mural type of unicystic ameloblastoma in a 32-year-old female patient with added emphasis on its histopathological importance.

Keywords: Metastasis, mural variant, unicystic ameloblastoma

How to cite this article:
Mahalingam R, Gunasekaran N, Bala D, Ravichandran D, Dhilipan P, Sivakumar D. Unicystic ameloblastoma: An unusual case report. SRM J Res Dent Sci 2020;11:220-3

How to cite this URL:
Mahalingam R, Gunasekaran N, Bala D, Ravichandran D, Dhilipan P, Sivakumar D. Unicystic ameloblastoma: An unusual case report. SRM J Res Dent Sci [serial online] 2020 [cited 2021 Mar 2];11:220-3. Available from:

  Introduction Top

Ameloblastomas are considered to be tumors which are relatively rare in occurrence and form a group of epithelial tumors showing both cystic and solid components. They are said to be benign in nature and most commonly locally aggressive.[1] The tumor is found to show an insidious growth pattern exhibiting varied clinical and histopathological patterns leading to a diagnostic dilemma.

The World Health Organization in the year 2017 had classified ameloblastoma under benign epithelial odontogenic tumors and further classified as ameloblastoma – unicystic type and ameloblastoma – extraosseous/peripheral type.

Unicystic ameloblastoma was first described by Robinson and Martinez in the year 1977 and referred to a cyst which histologically exhibits an ameloblast-like epithelium lining a cystic cavity. Radiographically, it appears similar to the cyst associated with unerupted tooth, commonly the dentigerous cyst, and sometimes mimics the envelopmental type of odontogenic keratocyst.[2]

Histopathologically most commonly, it shows a luminal or mural type of growth.[1] The mural type of growth is most often left unnoticed, and hence, analyzing the specimen histopathologically through serial sections is often made mandatory.

Thus, in this case report, we present a case of unicystic ameloblastoma exhibiting the mural type of growth.

  Case Report Top

A 32-year-old female patient came with a chief complaint of pain and swelling in the left lower back tooth region for the past 2 months. The history of presenting illness revealed that the pain was sharp and intermittent in nature and was associated with pus discharge. Medical history revealed no significant data.

Clinical examination revealed mild facial asymmetry on the left side of the face. The extraoral swelling was diffuse and not well circumscribed and was firm in consistency and was fixed.

The intraoral examination revealed a painful swelling in the buccal vestibule extending anteroposteriorly from the distal aspect of 35 tooth to the distal end of 37, measuring 4.5 cm × 2.5 cm in dimension [Figure 1]. The mucosa overlying the swelling did not show any ulceration or erythema, and the swelling was firm and tender on palpation.
Figure 1: Intraoral image showing buccal cortical expansion in relation to the left mandibular alveolus

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Panoramic radiograph revealed a well-defined multilocular radiolucency showing a characteristic soap bubble appearance interspersed with thin cortical bone [Figure 2]. There was evidence of apical root resorption in relation to 35 and displacement of root of 37 with impacted 38.
Figure 2: Orthopantomograph showed well-defined multilocular radiolucency

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The preoperative diagnosis of the lesion was given as ameloblastoma. An incisional biopsy was performed under local anesthesia, and the histopathological diagnosis was unicystic ameloblastoma – luminal type.

Based on the histopathological diagnosis of the incisional biopsy, enucleation of the lesion was performed under general anesthesia. The enucleated specimen was then sent for histopathological examination.

Microscopic examination revealed a cystic cavity with lining epithelium and connective tissue wall. The epithelial lining was 7–8 layer thick and ameloblastomatous in nature showing columnar and hyperchromatic basal cells and loosely arranged star-shaped superficial cells resembling stellate reticulum. The connective tissue wall showed loose to densely arranged collagen fibers and odontogenic epithelial islands [Figure 3] and [Figure 4]. The islands showed peripherally arranged columnar cells resembling ameloblastoma-like cells and centrally placed star-shaped cells resembling stellate reticulum-like cells. The connective tissue wall showed foci of chronic inflammatory cells predominantly lymphocytes were seen. Few extravasated red blood cells were also seen and trabeculae of bone were seen in the periphery. With the above-mentioned features, a diagnosis of unicystic ameloblastoma-mural type (follicular variant) was given.
Figure 3: Ameloblastomatous cystic lining and connective tissue wall

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Figure 4: Mural islands in the connective tissue wall

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Based on the clinical, radiographic, and microscopic features, the final diagnosis was established as unicystic ameloblastoma, mural variant exhibiting follicular pattern. Following treatment, the patient was followed for a period of 3 years with no evidence of recurrence till date.

  Discussion Top

Unicystic ameloblastoma is a rare lesion affecting the jaws. Most commonly, the mandible accounts for about 5%–15% of all ameloblastic lesions.[3],[4] About 50%–80% of the cases of unicystic ameloblastoma are found to be associated with impacted tooth. Various classifications have been put forth to describe different forms of unicystic ameloblastoma. And the commonly considered methods for classification being the ones given by Philipsen et al, Riechart and Ackermann et al and the modifications given by Gardener et al.

Pathogenesis involved in this type of ameloblastoma is unclear but often arises from the odontogenic apparatus or those cells that form the dental tissue. Many authors have highlighted that the possible source of tumor to be cell rest of malassez, cell rest of serres, predominantly from the dentigerous cyst and the surface epithelium of the oral cavity. The genetic basis of this tumor involves various genes, namely the PTCH (patched) gene, SHH (sonic hedgehog), and WNT. These genes encode for a specific protein which are commonly involved in tooth development are altered in various ways resulting in anomalous tooth formation.[5]

Typically unicystic ameloblastoma shows a unilocular radiographic picture which may or may not be associated with an unerupted tooth. Radiographically, the lesion may bear a resemblance to many cysts of the jaw, the most common being dentigerous cyst which is most commonly associated with unerupted tooth. Sometimes, unicystic ameloblastoma can also be misdiagnosed as a radicular cyst considering their radiographic feature. In the current case, the lesion showed a multilocular radiolucency. Multilocular radiolucencies can have a varied differential including odontogenic keratocyst, ameloblastoma, odontogenic myxoma, aneurysmal bone cysts, and so on. In these cases, histopathology becomes the gold standard in the diagnosis of these lesions.

Histological diagnosis of unicystic ameloblastoma requires vigilant analysis. In our initial incisional biopsy report, the histopathologic picture corresponded with the findings of unicystic ameloblastoma – luminal type. However, on microscopic examination of the excisional biopsy specimen, the histopathology report was suggestive of unicystic ameloblastoma – mural type.

This could be explained by partial removal of the tumor contents during the incisional biopsy and hence was not representative for the entire specimen. Mural types are found to recur following conservative management. In order to completely analyze the specimen completely, serial sections are to be made to rule out the presence of any mural pattern of growth into the connective tissue wall.[6]

Appropriate diagnosis of the type of unicystic ameloblastoma is mandatory for the assessment of the prognosis of the lesion and the purpose of treatment planning.[7] Considering unicystic ameloblastomas to be less aggressive than conventional ameloblastomas, they are often treated by enucleation or curettage.[8] However, mural types of unicystic ameloblastomas are found to recur the following conservative management and hence have to be managed in a similar way to that of solid ameloblastomas. The soft-tissue borders at the time of enucleation or curettage may also be examined by frozen sections, to ensure that complete removal of the lesion has been achieved.

  Conclusion Top

Unicystic ameloblastomas often show contrasting histological combinations making the treatment modalities more complex. The luminal and intraluminal types can be treated by simple enucleation, but the mural types require special attention and have to be treated aggressively similar to conventional ameloblastomas. These lesions often require long-term follow-up to check for recurrences. In reference to our case, the patient was followed for a period of 3 years with no evidence of recurrence till date.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Agani Z, Krasniqi HV, Recica J, Loxha MP, Kurshumliu F, Rexhepi A. Maxillary unicystic ameloblastoma: A case report. BMC Res Notes 2016;9:7-10.  Back to cited text no. 1
Gaudinat M, Samama M, Guyon A, Razouk O, Goudot P. Unicystic ameloblastoma mimicking a dentigerous cyst: Short case report. J Oral Med Oral Surg 2018;24:163-6.  Back to cited text no. 2
Figueiredo N, Dinkar A, Khorate M, Meena M. Calcifying epithelial odontogenic cyst of the mandible. J Oral Res Rev 2014;6:57.  Back to cited text no. 3
  [Full text]  
Nagalaxmi V, Sangmesh M, Maloth KN, Kodangal S, Chappidi V, Goyal S. Unicystic mural ameloblastoma: An unusual case report. Case Rep Dent 2013;2013:1-6.  Back to cited text no. 4
Jeddy N, Jeeva S, Jeyapradha T, Lakshmipathy P, Saikrishna P, Ananthalakshmi R. The molecular and genetic aspects in the pathogenesis and treatment of ameloblastoma. J Dr NTR Univ Heal Sci 2013;2:157.  Back to cited text no. 5
Panneerselvam K, Kavitha B, Panneerselvam E, Parameswaran A. Mural unicystic ameloblastoma mimicking odontogenic cyst. J Family Med Prim Care 2020;9:2524.  Back to cited text no. 6
Garcia NG, Oliveira DT, Rodrigues MT. Unicystic ameloblastoma with mural proliferation managed by conservative treatment. Case Rep Pathol 2016;2016:1-4.  Back to cited text no. 7
Gupta N, Saxena S, Rathod VC, Aggarwal P. Unicystic ameloblastoma of the mandible. J Oral Maxillofac Pathol 2011;15:228-31.  Back to cited text no. 8
  [Full text]  


  [Figure 1], [Figure 2], [Figure 3], [Figure 4]


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