Journal of Indian Academy of Oral Medicine and Radiology

: 2017  |  Volume : 29  |  Issue : 4  |  Page : 345--349

Nonexpansile Unicystic Ameloblastoma: A Rare Case Report

Supreet Jain1, Salona Kalra2, Ravleen Nagi1, Sumit Tiwari3,  
1 Department of Oral Medicine and Radiology, New Horizon Dental College and Research Institute, Bilaspur, Chhattisgarh, India
2 Department of Oral Medicine and Radiology, Triveni Institute of Dental Sciences Hospital and Research Centre, Bilaspur, Chhattisgarh, India
3 Department of Oral and Maxillofacial Surgery, New Horizon Dental College and Research Institute, Bilaspur, Chhattisgarh, India

Correspondence Address:
Dr. Supreet Jain
Department of Oral Medicine and Radiology, New Horizon Dental College and Research Institute, Sakri, Bilaspur, Chattisgarh


Ameloblastoma is the most common benign odontogenic tumor that has the potential to grow into a large size. Unicystic ameloblastoma (UA) is a variant of the solid or multicystic ameloblastoma. It is a rare (relative frequency 5–22%) benign, locally invasive odontogenic tumor of young age that mimics clinically and radiographically as an odontogenic cyst. Radiographically it may present as unilocualr or multilocular with cortical plate expansion. Conventional radiograph has less advantage to determine their extension into soft tissue. Hence, conventional tomography, cone-beam computed tomography, and magnetic resonance imaging may be used to determine expansion, root resorption and relation with adjacent structures. It has low recurrence rate after conservative therapy. Here, we present a rare case of nonexpansile UA with an unusual presentation in a young male patient.

How to cite this article:
Jain S, Kalra S, Nagi R, Tiwari S. Nonexpansile Unicystic Ameloblastoma: A Rare Case Report.J Indian Acad Oral Med Radiol 2017;29:345-349

How to cite this URL:
Jain S, Kalra S, Nagi R, Tiwari S. Nonexpansile Unicystic Ameloblastoma: A Rare Case Report. J Indian Acad Oral Med Radiol [serial online] 2017 [cited 2022 Oct 6 ];29:345-349
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WHO (1992) defined ameloblastoma as “a benign locally invasive polymorphic neoplasm consisting of proliferating odontogenic epithelium which usually has a follicular or a plexiform pattern lying in a fibrous stroma.”[1] Ameloblastomas are of three biologic variants: Cystic (unicystic), solid (multicystic), and peripheral. Unicystic ameloblastoma (UA) or cystogenic ameloblastoma was first described by Robinson and Martinez in 1977.[2] UA is the less encountered variant of the ameloblastoma, referring to those cystic lesions that show clinical and radiographic characteristics of an odontogenic cyst but in histological examination show a typical ameloblastomatous epithelium lining part of the cyst cavity, with or without luminal and/or mural tumor proliferation.[3] Ackermann et al. classified UA into mural ameloblastoma, luminal ameloblastoma, and ameloblastoma arising in dentigerous cysts (DCs). The relative frequency of occurrence of UA is between 5% and 22%.[4] UA commonly occurs in the second or third decade with no sexual or racial predilection. It is an asymptomatic lesion, frequently seen in the posterior mandible simulating odontogenic cyst.[5]

It has been suggested that epithelial deadhesion or intrinsic production of proteinases; enzymes that normally degrade central zone of the enamel organ after tooth development may be the cause of cystic degeneration of neoplasm. Recently, Kahn suggested human papilloma virus as a causative agent in the development of UA.[1] Here, we present a rare case of nonexpansile UA with an unusual presentation in a young male patient.

 Case Report

A 22-year-old male patient reported to the Department of Oral Medicine and Radiology with a complaint of pain in his lower right back teeth region since 2 days. Pain was dull and intermittent and aggravated on chewing. Patient had a history of trauma in his upper lip in an accident 5 years ago. All vitals were within normal limits. Extraoral examination revealed no gross asymmetry. Paresthesia was present over the right side of the jaw and lower lip region. Intraorally, there was mesioangular tilted 48 with recession and periodontal pocket in relation to 47 and 48 [Figure 1]a. On palpation, there was no cortical plate expansion. Paresthesia was present over right vestibular region and right half of tongue. On the basis of history and examination, a provisional diagnosis of keratocystic odontogenic tumor was made and differential diagnosis of DC, traumatic bone cyst (TBC) was given. Panoramic radiograph revealed a well-defined, unilocular radiolucency surrounded by corticated borders associated with 48 involving the right body of mandible extending from distal aspect of root of 45 till cementoenamel junction of 48 anteroposteriorly and superoinferiorly from alveolar crest mesial to 48 till lower border of mandible of approximately 5 × 4 cm in size. External root resorption was seen in 46 and 47. Inferior alveolar canal appeared to be discontinuous at apex of 47 and 48 region [Figure 1]b. Radiographic diagnosis of DC and differential diagnosis of keratocystic odontogenic tumor (KCOT), TBC, and UA was given. Blood investigations revealed that all parameters were within normal limits. Fine needle aspiration cytology showed straw-colored fluid [Figure 1]c. Surgical enucleation of cyst along with extraction of 46, 47, and 48 was done under general anesthesia and specimen was sent for histopathological examination [Figure 2]a and [Figure 2]b. Histopathological examination revealed cystic lumen lined by odontoblastic epithelium proliferating towards cystic capsular area forming anastomizing cords lined by tall columnar cells and centrally stellate reticulum like cells [Figure 3]a,[Figure 3]b,[Figure 3]c. The final diagnosis made was UA. Later after 6 months follow-up, patient was asymptomatic with no sign of recurrence [Figure 4]a and [Figure 4]b.{Figure 1}{Figure 2}{Figure 3}{Figure 4}


UA is a rare benign odontogenic tumor commonly occurring in the 2–3 decades of life and has recurrence rate of less than 25%.[2] It has typically unilocular radiographic appearance, macroscopically cystic in nature and has better response to conservative treatment, thus making it a unique entity.[1] The lesion is mostly asymptomatic. Commonly associated symptoms are painless swelling with expansion of cortical plates, unilocular lesion with sclerotic borders, impacted teeth, displacement, tipping, external root resorption, and root divergence. It mostly involves mandibular posterior body and ramus area and has no sex predilection.[5],[6],[7] In our case, tumor was seen in the right mandibular molar area and the patient had pain and paresthesia, but there was no swelling and expansion of cortical plates which was an unusual presentation for this case and lead us to give a provisional diagnosis of KCOT. Review of clinical and radiological features of few cases from literature has been summarized in [Table 1].{Table 1}

Preoperative diagnostic evaluation includes imaging and possible biopsy. Ameloblastomas on dental X-rays (pantomography) or plain films show a lytic lesion with scalloped margins, resorption of tooth roots, and impacted molars (unicystic).[8],[9] Although conventional radiograph helps to study the interface between the tumor and normal bone, it has less advantage to determine their expansion and extension into soft tissue. Hence, conventional tomography, cone-beam computed tomography (CBCT), and magnetic resonance imaging (MRI) may play a significant role. Computed tomography (CT) is the most useful diagnostic imaging modality for the evaluation of cortical destruction (revealing a window for biopsy), cortical plate expansion, root resorption, soft tissue extension, and relation with adjacent structures.[8] The appearance on CBCT is same as in plain films, then also CBCT is highly recommended as it aids in assessing the periphery, relationship to the adjacent structures and can also detect perforation in the outer cortex. MRI scores more over CT for appreciating soft tissue projections into cystic cavity. MRI is useful for ameloblastomas arising from the maxilla as it helps to characterize extension to the orbit, paranasal sinuses, and skull base. T1-weighted images have intermediate signal, and T2-weighted images have intermediate to high signals.[10] Currently, there is an emerging interest in the applications of ultrasonography (USG), a noninvasive, real time modality to procure information of blood flow and also to distinguish cystic and solid components within the tumors. PET-CT is generally used for metastatic ameloblastoma, where it may aid with staging of the distant metastasis.[8],[9] Radiographically, it may appear as a pericoronal unilocular, pericoronal scalloped, periapical unilocular, inter-radicular, and multilocular radiolucency.[6],[11] Clinical and radiological features of UA may mimic other odontogenic cysts and tumors thus making it difficult to diagnose. The differential diagnosis for this lesion is discussed in [Table 2].[5],[12]{Table 2}

Histopathologically, the minimum criteria for diagnosing UA are the demonstration of a single cystic sac lined by odontogenic (ameloblastomatous) epithelium often seen only in focal areas.[4] Ackermann et al. classified the histological subtypes into three patterns, namely luminal (type 1, tumor confined to luminal surface of cyst), intraluminal (type 2, nodular proliferation into the lumen without infiltration of tumor cells into connective tissue wall), and mural patterns (type 3, invasive islands of ameloblastic epithelium into the connective tissue not involving the entire epithelium).[7],[13] In the present case, lesion was associated with impacted tooth and was of mural type with cystic lumen lined by odontoblastic epithelium proliferating towards cystic capsular area thus forming anastomizing cords. UA is less aggressive, has lower recurrence rate, and responds favorably to conservative treatments such as marsupilization, enulceation and curettage, enucleation followed by application of carnoy's solution, thermal or chemical cauterization, cryotherapy, and even radiotherapy or chemotherapy.[1],[10],[14] In our case, surgical enucleation under general anesthesia was done and patient was regularly followed up. In the present case, patient was asymptomatic after 6 months follow-up.


UA although less aggressive than multicystic ameloblastoma, should be included in the differential diagnosis of swellings of maxillofacial region. In most cases, UA has been reported to cause jaw expansion but our case was unique as there was no expansion of cortical plates and dentists should familiarize themselves with such cases to prevent their under-diagnosis in clinical practice. Complete clinical, radiological, and histological examination contributes to the final and prompt diagnosis of the lesion. Although conservative treatment is preferred for patients, long-term follow-up of patients is mandatory to prevent recurrence of lesion and for better prognosis.

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.

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Conflicts of interest

There are no conflicts of interest.


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