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 Table of Contents  
CASE REPORT
Year : 2016  |  Volume : 28  |  Issue : 4  |  Page : 420-423

Unicystic ameloblastoma of mandible: Nondentigerous variant – A rare case report


1 Department of Oral Medicine and Radiology, Sri Venkata Sai Institute of Dental Sciences, Mahabubnagar, Telangana, India
2 Department of Oral and Maxillofacial Surgery, Sri Venkata Sai Institute of Dental Sciences, Mahabubnagar, Telangana, India
3 Department of Oral and Maxillofacial Pathology, Sri Venkata Sai Institute of Dental Sciences, Mahabubnagar, Telangana, India

Date of Submission23-Mar-2016
Date of Acceptance23-Dec-2016
Date of Web Publication21-Feb-2017

Correspondence Address:
Dr. Swapna Tipirisety
Department of Oral Medicine and Radiology, Sri Venkata Sai Institute of Dental Sciences, Appannapally, Mahabubnagar, Telangana - 509 002
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0972-1363.200644

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   Abstract 

Ameloblastomas are benign epithelial odontogenic tumors. The World Health Organization (2005) classified ameloblastomas into solid/multicystic, extraosseous/peripheral, desmoplastic and unicystic types. Unicystic ameloblastoma (UA) is a less frequently occurring tumor and accounts for 10 to 15% of all the intraosseous ameloblastomas. Ninety percent of the UAs are found in the mandible with predominance towards molar-ramus region. Approximately 50–80% of UAs are associated with impacted tooth (dentigerous variant). This case report is an effort to bring forth a case of UA in a 35-year-old female who presented with an asymptomatic swelling involving the right and left parasymphsis region through the midline, which is uncommon for UA and is not associated with an impacted tooth (nondentigerous variant). The lesion was confirmed by histopathological evaluation, treated by complete enucleation and curettage with extraction of teeth number 31 to 35 and 41 to 45, followed by chemical cauterization with 5% Carnoy's solution, and rehabilitated with fixed partial denture after 7 months.

Keywords: Ameloblastomatous epithelium, Carnoy's solution, enucleation, impacted tooth, unicystic


How to cite this article:
Kubbi JR, Tipirisety S, Dubbudu R, Oruganti RV. Unicystic ameloblastoma of mandible: Nondentigerous variant – A rare case report. J Indian Acad Oral Med Radiol 2016;28:420-3

How to cite this URL:
Kubbi JR, Tipirisety S, Dubbudu R, Oruganti RV. Unicystic ameloblastoma of mandible: Nondentigerous variant – A rare case report. J Indian Acad Oral Med Radiol [serial online] 2016 [cited 2019 Oct 17];28:420-3. Available from: http://www.jiaomr.in/text.asp?2016/28/4/420/200644


   Introduction Top


Unicystic ameloblastoma (UA) was first described as a distinct variant of ameloblastoma by Robinson and Martinez in 1977.[1],[2],[3] More than 90% of UAs occur in the mandible, usually in the posterior region.[4] Approximately 50–80% of UAs are associated with impacted tooth, the mandibular third molar being the most commonly involved.[5] The present case is of significant importance because of its uncommon location and absence of an impacted tooth. To the best of our knowledge, very few cases of UA of mandible crossing the midline have been reported in literature.


   Case Report Top


A 35-year-old female patient presented with a chief complaint of swollen gums in the lower front tooth region for one and half year. Swelling was small in size initially, which gradually progressed to the present size, and was not associated with pain. Past medical and dental history was insignificant. Extraoral examination revealed an ill-defined swelling of size approximately 3 × 4 cm, involving the right and left parasymphysis region through the midline. Superoinferiorly, the swelling extended from the mentolabial sulcus (causing its obvious obliteration) to the inferior border of the mandible [Figure 1]a. The surface of the swelling appeared normal. The swelling was nontender and soft-to-firm in consistency. Intraoral examination revealed an ill-defined swelling of size approximately 3.5 × 6 cm extending from 35 to 45, superiorly up to the gingival crevice, inferiorly obliterating the labial and bilateral buccal vestibules [Figure 1]b and [Figure 1]c. Swelling slightly extended into the lingual vestibule causing its obliteration [Figure 1]d. The overlying mucosa on the labial aspect appeared to be stretched. On palpation, the swelling was nontender and soft in consistency on labial and buccal aspect, and hard in consistency on the lingual aspect. Palpation revealed expansion of labial, buccal and lingual cortical plates with egg shell crackling sign on the labial aspect. Grade I and II mobility was noticed with 43, 44, 45, and 31, 32, 33, 34, 35, 41, 42, respectively. A provisional diagnosis of central gaint cell granuloma was made. Clinical differential diagnosis of a variant of ameloblastoma was made. Thermal pulp vitality test revealed 31, 32, 33, 34, 35, 41, 42, 43, 44 and 45 to be nonvital. On aspiration, a clear straw-colored fluid was obtained from the labial aspect.
Figure 1: (a) Extraoral photograph showing facial asymmetry over the chin region. (c-d) intraoral clinical photographs

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Mandibular occlusal radiograph [Figure 2]a revealed expansion of the right and left buccal cortical plates and floating tooth appearance in the anterior region because of loss of labial and lingual cortical plates in this region. Orthopantomogram disclosed a large well-defined unilocular radiolucency with sclerotic border of size approximately 3 × 7 cm extending from the lower left first molar to right first molar causing severe root resorptions with 31, 32, 33, 34, 35, 41, 42, 43, 44 and 45. Mild displacement with mesial inclination was noticed with 41, 42 and 43. Mild displacements with distal inclination of 31 and mesial inclination of 33 were noticed [Figure 2]b. Computed tomography (CT) revealed a large osteolytic lesion in the anterior and to some extent in the posterior region of mandible with floating tooth appearance in the anterior region [Figure 2]c,[Figure 2]d,[Figure 2]e. Based on the radiographic features, radiographic differential diagnoses of a variant of ameloblastoma and keratocystic odontogenic tumor (KCOT) were made.
Figure 2: (a) Mandibular occlusal radiograph showing expansion of bilateral buccal cortical plates and floating tooth appearance in the anterior region. (b) Orthopantomograph showing unilocular well-defined radiolucent lesion from 36 to 46 and severe root resorption in 31, 32, 33, 34, 35, 41, 42, 43, 44, and 45. (c) Axial CT view showing a large osteolytic lesion involving the anterior and to some extent the posterior region of mandible. (d, e) Reconstructed 3D view showing a large osteolytic lesion of mandible with floating tooth appearance in the anterior region

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An incisional biopsy of the lesion was carried out which revealed a microscopic diagnosis of infected cystic capsule. Root canal treatment was performed in 36 and 46 before surgery. Under general anesthesia, enucleation and curettage of the lesion was performed to completely remove the cystic lesion with extraction of teeth numbered 31–35 and 41–45, followed by chemical cauterization with 5% Carnoy's solution [Figure 3]a and [Figure 3]b. The excised specimen showed a well-defined cystic lumen lined by stratified squamous odontogenic epithelium exhibiting basal tall columnar ameloblast-like cells and superficial stellate reticulum-like tissue. Lining epithelium showed mural proliferation into the underlying connective tissue with subepithelial eosinophilic hyalinization. The underlying connective tissue stroma showed delicate-to-dense collagen fibre bundles with chronic inflammatory cell infiltrate composed of lymphocytes and blood capillaries [Figure 3]c and [Figure 4]a. The deeper connective tissue revealed few ameloblastic follicles showing typical tall columnar peripheral ameloblast-like cells and central stellate reticulum-like tissue [Figure 4]b. Based on the above microscopic features, a final diagnosis of UA (mural) of the mandible was made. The patient was rehabilitated with fixed partial denture after 7 months. Patient is on regular follow-up since a year with no signs of recurrence, both clinically and radiographically [Figure 5]a and [Figure 5]b.
Figure 3: (a) Intraoperative image. (b) Volume of gross specimen. (c) Photomicrograph (10×) H and E stained sections showing stratified squamous odontogenic epithelium exhibiting proliferation of lining epithelium into the underlying connective tissue with basal tall columnar ameloblast-like cells (yellow arrow) and superficial stellate reticulum like tissue (orange arrow)

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Figure 4: (a) Photomicrograph (20×) H and E stained sections showing mural proliferation of lining epithelium into the underlying connective tissue with subepithelial eosinophilic hyalinization (yellow arrow). (b) Photomicrograph (10×) H and E stained sections showing deeper connective tissue with few ameloblastic follicles (yellow arrows) showing typical peripheral tall columnar ameloblast-like cells and central stellate reticulum like tissue

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Figure 5: (a) One year follow-up intraoral clinical photograph showing rehabilitation with fixed partial denture. (b) One year follow-up radiograph

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   Discussion Top


According to Robert and Diane, UA may arise from reduced enamel epithelium, or may occur as a transformation of dentigerous cyst into UA, or due to cystic degeneration of solid/multicystic ameloblastoma.[2],[4] Usually UA occurs in young individuals (second to third decades of life)[3] with 50% of these lesions diagnosed during the second decade of life.[6],[7] Approximately 50–80% of UAs are associated with impacted tooth mostly mandibular third molars termed as dentigerous variant, and the one which is not associated with impacted teeth is termed as nondentigerous variant. The “dentigerous” variant occurs approximately 8 years earlier than the “nondentigerous” variant. UAs are usually asymptomatic.[3]

Radiographically, six patterns have been identified for UA, ranging from well-defined unilocular-to-multilocular ones, but mainly divided into unilocular and multilocular patterns with predominance towards unilocular pattern in all studies of UA, especially in cases associated with impacted tooth.[4],[5] The unilocular-to-multilocular ratio is 4.3:1 for the dentigerous variant, and for the nondentigerous variant, this ratio is 1.1:1.[3] It is very difficult to differentiate the dentigerous variant of UA both clinically and radiographically from odontogenic cysts when compared to the nondentigerous variant. The nondentigerous variant of UA may resemble residual cyst or KCOT.[4]

Based on the clinicopathologic study performed in 57 cases of UA, Ackermann classified this entity into 3 histologic groups, namely, luminal, intraluminal/plexiform, and mural.[3],[8] In another histologic subgrouping (modified after Ackermann et al.) by Philipsen and Reichart, UA was classified into 4 subtypes, namely, subtype 1 luminal UA, subtype 1.2 luminal and intraluminal UA, subtype 1.2.3 luminal, intraluminal, and intramural UA, and Subtype 1.3 luminal and intramural UA.[5]

There are different treatment modalities for UA which include enucleation, curettage, marsupialization and marginal resection.[2] The present scientific literature recommends that UA should be treated in a conservative manner (enucleation, curettage, and marsupialization) when compared to solid or multicystic ameloblastomas on account of their less aggressive biological behavior. The response of the UA to conventional treatment is favorable.[2],[3] Subtypes of UA 1 and 1.2 can be treated conservatively (careful surgical enucleation), whereas subtypes 1.2.3 and 1.3 should be treated aggressively (radical resection).[5],[6]

Recurrence depends on histological variant and treatment type. Mural UA has the highest recurrence rate. According to Li et al., the recurrence rate for mural UA is 35.7%.[9] According to Lau et al., resection, enucleation, enucleation along with application of Carnoy's solution, marsupialization, followed by enucleation have recurrence rates of 3.6%, 30.5%, 16%, and 18%, respectively.[6] Because UA is cystic, well-localized and surrounded by fibrous capsule, the prognosis is good. However, when it breaches the periphery of the fibrous capsule it behaves more aggressively.[10] Because the recurrence of UA is long delayed, long-term postoperative follow-up is required.[3],[10]


   Conclusion Top


UA shares clinical and radiographic features with other odontogenic lesions, and hence the diagnosis cannot be based on clinical and radiographic features alone. In the present case, the final diagnosis of UA was made only after the histopathological examination. Thus histopathological examination is mandatory for arriving at a final diagnosis of UA. Long-term postoperative follow-up is mandatory because the recurrence of UA may be long delayed.

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

Nil.

Conflicts of interest

There are no conflicts of interest.

 
   References Top

1.
Robinson L, Martinez MG. Unicystic ameloblastoma: A prognostically distinct entity. Cancer 1977;40:2278-85.  Back to cited text no. 1
    
2.
Babu N, Charles NS, Rai R, Mathur S, Runwal SH. Unicystic ameloblastoma of mandible treated with an innovative approach: A clinical case report. J Clin Diagn Res 2015;9:11-3.  Back to cited text no. 2
    
3.
Figueiredo NR, Meena M, Dinkar AD, Malik S, Khorate M. Unicystic ameloblastoma presenting as multilocular radiolucency in the anterior mandible. J Den Res Dent Clin Dent Prospect 2015;9:199-204.  Back to cited text no. 3
    
4.
Bajpai M, Agarwal D, Bhalla A, Kumar M, Garg R, Kumar M. Multilocular unicystic ameloblastoma of mandible. Case Rep Dent 2013;2013:835892.  Back to cited text no. 4
    
5.
Singh A, Shaikh S, Samadi FM, Shrivastava S, Verma R. Maxillary unicystic ameloblastoma: A review of the literature. Natl J Maxillofac Surg 2011;2:163-8.  Back to cited text no. 5
[PUBMED]  Medknow Journal  
6.
Ramesh RS, Manjunath S, Ustad TH, Pais S, Shivakumar K. Unicystic ameloblastoma of the mandible- An unusual case report and review of literature. Head Neck Oncol 2010;2:1:1-5  Back to cited text no. 6
    
7.
Paikkatt VJ, Sreedharan S, Kannan VP. Unicystic ameloblastoma of the maxilla: A case report. J Indian Soc Pedod and Prev Dent 2007;25:106-10.  Back to cited text no. 7
    
8.
Bhushan NS, Rao NM, Navatha M, Kumar BK. Ameloblastoma arising from a dentigerous cyst: A case report. J Clin Diagn Res 2014:8:23-5.  Back to cited text no. 8
    
9.
Samuel S, Mistry FK, Chopra S, Pillai A. Unicystic ameloblastoma with mural proliferation: Conservative or surgical approach? BMJ Case Rep 2014;2014:bcr2014206273.  Back to cited text no. 9
    
10.
Saravanakumar B, Parthiban J, Aarthi Nisha V, Sarumathi T, Prakash CA. Unicystic ameloblastoma of the mandible– Report of two cases with review of literature. J Clin Diagn Res 2014;8:7-9.  Back to cited text no. 10
    


    Figures

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



 

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