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Table of Contents   
CASE REPORT  
Year : 2020  |  Volume : 31  |  Issue : 6  |  Page : 987-990
Paediatric unicystic ameloblastoma – A report of 2 cases


1 Department of Oral Pathology and Microbiology, Manipal College of Dental Sciences, Manipal, Manipal Academy of Higher Education, Karnataka, India
2 Depatment of Oral Pathology and Microbiology, Kusumdevi Sunderlal Dugar Jain Dental College, Kolkata, India
3 Consultant, Craniofacial Services, Hannah Joseph Institute of Neurosciences, Madurai, Tamil Nadu, India

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Date of Submission01-Sep-2018
Date of Decision28-Oct-2019
Date of Acceptance10-Jul-2020
Date of Web Publication22-Mar-2021
 

   Abstract 


Unicytic ameloblastoma is a variant of ameloblastoma encompassing about 6% of ameloblastomas. They represent cystic lesions that reveal clinical and radiographic features of a cyst, but the histopathological features demonstrate a typical ameloblastomatous epithelium lining the cyst. Plexiform unicystic ameloblastoma, a variant of unicystic ameloblastoma refers to the pattern of proliferation where one or more nodules of ameloblastomatous epithelium project from the cystic lining into the lumen demonstrating an edematous plexiform pattern. The lesion is seen more commonly in the third and fourth decades of life with less than 10% of cases being reported in the first decade. Here, we report two cases of unicystic ameloblastoma in paediatric patients. This report also aims to provide an insight on the pathogenesis and treatment aspects of this distinct entity.

Keywords: 1st decade, paediatric management, plexiform, unicystic ameloblastoma

How to cite this article:
Kulkarni S, Sen S, Chandrashekar C, Narayanaswamy V, Radhakrishnan R. Paediatric unicystic ameloblastoma – A report of 2 cases. Indian J Dent Res 2020;31:987-90

How to cite this URL:
Kulkarni S, Sen S, Chandrashekar C, Narayanaswamy V, Radhakrishnan R. Paediatric unicystic ameloblastoma – A report of 2 cases. Indian J Dent Res [serial online] 2020 [cited 2021 Nov 27];31:987-90. Available from: https://www.ijdr.in/text.asp?2020/31/6/987/311663



   Introduction Top


Ameloblastoma is a common benign odontogenic tumor, locally aggressive with a high tendency to recur, consisting of proliferating odontogenic epithelium in a fibrous stroma as defined by WHO.[1] It has been broadly classified into four subtypes, the classic solid/multicystic, extra-osseous/peripheral, desmoplastic and unicystic.[2] Unicystic ameloblastoma (UA) refers to those cystic lesions that on gross and radiographic examination resemble odontogenic cysts, but histologically reveal an ameloblastomatous epithelium lining the cystic cavity.[3] Biologically, this lesion is less aggressive than the multicystic or solid varieties.[2] Plexiform unicystic ameloblastoma (PUA) is a variant of UA that is also referred to as intraluminal unicystic ameloblastoma which shows one or more nodules of amelobastoma that project from the cystic lining into the lumen, demonstrating a plexiform pattern similar to the plexiform pattern of conventional ameloblastoma.[4]

Ameloblastomas most often affect individuals in the third and fourth decades of life and are rare in children. The unicystic variant has been detected in a comparatively younger population but less than 10% of paediatric cases occur in children below the age of 10 years.[5],[6],[7] We herewith report two cases of UA in patients in their first decade. We also attempt to shed light on clinical presentation, pathogenesis and treatment aspects of this lesion.


   Case Report Top


Case 1

A 6-year old boy presented with the chief complaint of an asymptomatic slow-growing swelling in the right lower jaw since six months. Extra-oral examination revealed a diffuse unilateral swelling in the right mandible. Intra-orally, the enlargement extended from the right mandibular canine to the retromolar region with an obliterated mucobuccal sulcus [Figure 1]. The swelling was well defined, firm and non-tender on palpation.
Figure 1: Intraoral view revealing a swelling on the right side of the mandible with obliteration of the mucobuccal sulcus

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Computed tomography (CT) imaging showed a well-defined hypodense area in the right mandible measuring approximately 3 × 7 cm. It extended anteriorly from the symphysis upto the ramus and condylar neck, and was surrounded by well-corticated borders. A hyperdense mass was seen within the hypodense area, suggestive of a developing tooth [Figure 2]. Based on the confluence of the clinical and radiographic findings, a differential diagnosis of dentigerous cyst, odontogenic keratocyst and UA were considered. Taking into account the age of the patient and the advent of differential diagnosis, enucleation with curettage and peripheral ostectomy were performed along with extraction of the involved teeth. The entire specimen along with the extracted teeth was sent for the histopathological evaluation.
Figure 2: Sagittal CT scan of the lesion

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Histopathological examination revealed a large cystic lumen lined by 2–3 layers of epithelial cells, with a superficial layer of round to stellate-shaped cells suggestive of stellate reticulum. The basal layer consisted of hyperchromatic columnar cells which were at places ameloblast-like in appearance, exhibiting a reverse polarity of the nuclei and subnuclear vacuolization [Figure 3]a. Hyalinisation was evident at places in the connective tissue stroma adjacent to the proliferating epithelium. The nodular area of the cystic specimen showed proliferating odontogenic epithelium projecting into the cystic lumen with a plexiform pattern [Figure 3]b. Intervening connective tissue showed marked vascularity and inflammation. Few giant cells, foamy macrophages and psammomatous calcifications were seen at the periphery of the connective tissue capsule. The above features, in correlation with the clinical presentation, were suggestive of PUA.
Figure 3: A cystic lumen lined by odontogenic epithelial cells, with the basal layer comprising of ameloblast-like cells and superficial cells resembling stellate reticulum (a), a nodular area with plexiform pattern projecting into the cystic lumen (b)

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Case 2

A 5-year old girl reported to the dental clinic with the chief complaint of swelling in the left upper region of the jaw since 6 months. Extra-oral examination revealed a diffuse unilateral swelling in the upper left maxilla. Intra-oral examination revealed swelling that was tender on palpation and the overlying mucosa was erythematous.

Cone beam computed tomography (CBCT) and CT imaging were done which revealed erupting canine and a hypodense area with respect to the upper left maxillary jaw. The lesion extended from the region of upper deciduous canine to the deciduous second molar [Figure 4]a, [Figure 4]b. Thus correlating with clinical and radiographic findings, differential diagnosis comprising of dentigerous cyst, odontogenic keratocyst and UA were considered. Enucleation with curettage along with extraction of the involved teeth was done. The entire specimen along with the extracted teeth was sent for the histopathological evaluation.
Figure 4: (a) CBCT, (b) CT scan of the lesion

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The histopathological findings [Figure 5] were similar to those of Case 1, except the proliferating odontogenic epithelium into the cystic cavity was not seen and, in addition, the lesion close to the tooth revealed the lining epithelium resembling the reduced enamel epithelium. The lesion was signed out as unicystic ameloblastoma.
Figure 5: Histopathologic picture of case 2

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   Discussion Top


Unicystic ameloblastoma, a variant of ameloblastoma, was first described by Robinson and Martinez in 1977.[8] These lesions represent 5–23% of ameloblastomas and are frequently found to occur between the second and third decades of life[3] having a marginally younger age of presentation than its solid counterpart. However, its occurrence in children in the first decade of life is rare. The mandibular angle and symphysis remain the most common sites affected in children.[5]

The term UA is used to describe an ameloblastoma, which is essentially a well-defined monocystic cavity, with a lining focally but rarely entirely composed of ameloblastomatous epithelium.[3] However, a diagnosis with specification of the subtype is necessary as it has an implication on the biological behaviour, treatment and prognosis.

The PUA presents as one or more ameloblastomatous nodule projecting into the lumen of the cyst, arranged in a plexiform pattern.[4] The basal cells are usually unremarkable and do not fulfil the criteria of Vickers and Gorlin for ameloblastoma.[9] Thus, the sole basis of its resemblance to plexiform ameloblastoma is the plexiform pattern of epithelial strands.[4] The terms used to designate this entity included 'proliferation of hyperplastic epithelium in the wall of a cyst', 'pseudo-ameloblastomatous change in the wall of a cyst', 'odontogenic papilloma' and 'ameloblastomatoid cyst'.[9] However, the occurrence of this pattern was seen in association with a histological characteristic ameloblastoma in a significant number of cases,[4] including the present case. This led to the conclusion that the plexiform pattern of proliferating epithelium is in fact ameloblastoma, which does not exhibit the usually accepted histologic criteria for this tumour.

PUA is seen predominantly in the mandible with only one case being reported in the maxilla.[10] Intraoral displacement of the adjacent teeth may be seen and occasionally there may be associated partial anodontia or delayed eruption due to an impediment in the eruption process.

A unilocular radiolucency is a usual radiographic finding of PUA along with the displacement or resorption of the roots of neighbouring teeth.[4] Association with an impacted tooth is another typical trait.[4] These features simulate other entities such as a dentigerous cyst and odontogenic keratocyst. CT scan and magnetic resonance imaging (MRI) are helpful in determining and delineating the extent of the lesion. However, imaging is not pathognomonic and microscopic examination remains the mainstay of diagnosis.

The pathogenesis of UAs remains elusive. Some believe they arise due to the cystic degeneration of solid ameloblastoma following epithelial dysadhesion due to defective desmosomes or due to the intrinsic production of proteinases, which degrade the central zone of the enamel organ after tooth development.[2] Others believe they arise due to ameloblastomatous change in a pre-existing cyst.[11]

It is believed that UA is a biologically less aggressive type of ameloblastoma with a relatively low recurrence rate than the solid variant.[8] UA cases show longer disease-free survival period compared to the other variants. However, the management of UA remains controversial. Most surgeons believe in a conservative approach to this lesion and perform enucleation, surgically shelling the entire lesion out of the bone, succeeded by a regular follow up regime. This method is particularly relevant in children, where the preservation of facial bone structure is of paramount importance for both physical and psychological development.[7] However, a recurrence rate of 10.7% to 25% has been reported following treatment only by enucleation or curettage in cases where mural growth is present.[7] Infiltration of the tumor into the cystic wall constitutes a so-called solid component indicating a radical surgical approach when treating mural ameloblastoma.[12]

The correlation of clinical and histological parameters with proliferative marker Ki-67 showed that invading islands of mural or intramural variants have significantly higher Ki-67 labelling index than PUA. Lectin histochemistry of ameloblastomas, conducted to understand the biologic behaviour, revealed that the PUA exhibited the same cell membrane glycoproteins as the other variants of ameloblastoma, but expressed in less intensity and this suggests less aggressiveness compared to other variants of ameloblastoma.[13] Elevated neovascularisation and extracellular matrix metalloproteinase (MMP2 and MMP9) expression have been reported in the mural ameloblastomas.[14] These are probably the indicators of the aggressive nature of the mural variant and radical treatment involving marginal or segmental resection is justified.

In view of the growth potential and bone regeneration capacity in children, a conservative treatment is recommended in the first instance[15],[16] and an aggressive therapy for any recurrence. It is also suggested that a conservative treatment may be augmented by physicochemical treatment such as liquid nitrogen cryospray or Carnoy's solution, but long-term studies of these techniques are yet to be carried out.[16],[17] Although the possibility of a unicystic lesion might be inferred from an incisional biopsy, accurate diagnosis only can be made by thorough sampling of the entire specimen.[18]


   Conclusion Top


This paper brings to light two cases of unicystic ameloblastoma occurring in the first decade. Excisional biopsy should be advocated for all unilocular lesions and the treatment approach should be tailored based on the existing clinical situation and histological evidence. A conservative approach to treatment is important, particularly in paediatric patients as the growth of the jaws is not complete and injudicious radical resections may lead to deformity and dysfunction. The treatment modality gets complicated in paediatric patients due to factors such as continuous facial growth, greater percentage of cancellous bone, increased bone turnover and the presence of unerupted teeth. A regular post-surgical follow up is recommended for these patients.

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.
Gardner DG, Heikinheimo K, Shear M, Philipsen HP, Coleman H. Ameloblastomas. In: Barnes L, Eveson JW, Reichart P. Sidransky D, editors. World Health Organization Classification of Tumors. Pathology and Genetics. Head and Neck Tumours. Lyon: IARC Press; 2005. p. 296-300.  Back to cited text no. 1
    
2.
Hertog D, Bloemena E, Aartman IH, van-der-Waal I. Histopathology of ameloblastoma of the jaws; some critical observations based on a 40 years single institution experience. Medicina Oral Patología Oral Y Cirugía Bucal 2012:17:76-82.  Back to cited text no. 2
    
3.
Oliveira-Neto HH, Spíndula-Filho JV, Dallara MC, Silva CM, Mendonça EF, Batista AC. Unicystic ameloblastoma in a child: A differential diagnosis from the dentigerous cyst and inflammatory follicular cyst. J Dent Child (Chic) 2007;74:245-9.  Back to cited text no. 3
    
4.
Gardner DG, Corio RL. Plexiform unicystic ameloblastoma: A variant of ameloblastoma with a low recurrence-rate after enucleation. Cancer 1984;53:1730-5.  Back to cited text no. 4
    
5.
Ord RA, Blanchaert RH Jr, Nikitakis NG, Sauk JJ. Ameloblastoma in children. J Oral Maxillofac Surg 2002;60:762-70.  Back to cited text no. 5
    
6.
Castro-Silva II, Israel MS, Lima GS, de Queiroz Chaves Lourenço S. Difficulties in the diagnosis of plexiform ameloblastoma. Oral Maxillofac Surg 2012;16:115-8.  Back to cited text no. 6
    
7.
Scariot R, da Silva RV, da Silva Felix W Jr, da Costa DJ, Rebellato NL. Conservative treatment of ameloblastoma in child: A case report. Stomatologija 2012;14:33-6.  Back to cited text no. 7
    
8.
Robinson L, Martinez MG. Unicystic ameloblastoma: A prognostically distinct entity. Cancer 1997;40:2278-85.  Back to cited text no. 8
    
9.
Gardner DG. Plexiform unicystic ameloblastoma: A diagnostic problem in dentigerous cysts. Cancer 1981;47:1358-63.  Back to cited text no. 9
    
10.
Gardner DG, Morton TH Jr, Worsham JC. Plexiform unicystic ameloblastoma of the maxilla. Oral Surg Oral Med Oral Pathol 1987;63:221-3.  Back to cited text no. 10
    
11.
Dunsche A, Babendererde O, Lüttges J, Springer IN. Dentigerous cyst versus unicystic ameloblastoma-differential diagnosis in routine histology. J Oral Pathol Med 2003;32:486-91.  Back to cited text no. 11
    
12.
Aguirre A, Takai Y, Meenaghan M, Neiders ME, Natiella JR. Lectin histochemistry of ameloblastomas and odontogenic keratocysts. J Oral Pathol Med 1989;18:68-73.  Back to cited text no. 12
    
13.
Sah P, Menon A, Kamath A, Chandrashekar C, Carnelio S, Radhakrishnan R. Role of immunomarkers in the clinicopathological analysis of unicystic ameloblastoma. Disease Markers 2013;35481-8.  Back to cited text no. 13
    
14.
Huang IY, Lai ST, Chen CH, Chen CM, Wu CW, Shen YH. Surgical management of ameloblastoma in children. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2007;104:478-85.  Back to cited text no. 14
    
15.
Pogrel MA, Montes DM. Is there a role for enucleation in the management of ameloblastoma? Int J Oral Maxillofac Surg 2009;38:807-12.  Back to cited text no. 15
    
16.
Zhang J, Gu Z, Jiang L, Zhao J, Tian M, Zhou J, Duan Y. Ameloblastoma in children and adolescents. Br J Oral Maxillofac Surg 2010;48:549-54.  Back to cited text no. 16
    
17.
Gardner DG. Some current concepts on the pathology of ameloblastomas. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1996;82:660-9.  Back to cited text no. 17
    
18.
Ackermann GL, Altini M, Shear M. The unicystic ameloblastoma: A clinicopathologic study of 57 cases. J Oral Pathol 1988;17:541-6.  Back to cited text no. 18
    

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Correspondence Address:
Dr. Raghu Radhakrishnan
Professor, Department of Oral Pathology and Microbiology, Manipal College of Dental Sciences, Manipal, Manipal Academy of Higher Education, Manipal - 576 104, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijdr.IJDR_670_18

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    Figures

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



 

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