|Year : 2014 | Volume
| Issue : 3 | Page : 215-218
Non dentigerous variant of unicystic ameloblastoma: A case report
R Aravindhan1, KT Magesh1, P Suresh Kumar2, T Elangovan1, M Sathyakumar1
1 Department of Oral and Maxillofacial Pathology, SRM Kattankulathur Dental College, Potheri, Kattankulathur, Tamil Nadu, India
2 Department of Oral and Maxillofacial Surgery, SRM Kattankulathur Dental College, Potheri, Kattankulathur, Tamil Nadu, India
|Date of Web Publication||14-Aug-2014|
Department of Oral and Maxillofacial Pathology, SRM Kattankulathur Dental College, Potheri, Kanchipuram, Tamil Nadu
Source of Support: None, Conflict of Interest: None
Unicystic ameloblastoma is one of the placid jaw tumors comprising about 6-15% of ameloblastoma, it stands unexampled when it comes to the pathomorphological features. We discuss a case of unicystic ameloblastoma that is consonant with the nondentigerous multilocular unicystic ameloblastoma. The case was initially misdiagnosed as ameloblastic fibroma in a private diagnostic centre. Upon examining the resected specimen, we derived at the diagnosis of unicystic ameloblastoma, 1.2.3 type. The age of our case is also akin to the previous literature.
Keywords: Ameloblastoma, Odontogenic tumors, Unicystic ameloblastoma
|How to cite this article:|
Aravindhan R, Magesh K T, Kumar P S, Elangovan T, Sathyakumar M. Non dentigerous variant of unicystic ameloblastoma: A case report. SRM J Res Dent Sci 2014;5:215-8
|How to cite this URL:|
Aravindhan R, Magesh K T, Kumar P S, Elangovan T, Sathyakumar M. Non dentigerous variant of unicystic ameloblastoma: A case report. SRM J Res Dent Sci [serial online] 2014 [cited 2022 May 16];5:215-8. Available from: https://www.srmjrds.in/text.asp?2014/5/3/215/138780
| Introduction|| |
Oral health care professionals do encounter a variety of diseases in daily routine, some are harmless, and on the other hand few are potentially lethal. Odontogenic tumors and other lesions related to the jawbones have for years been recognized as a well-defined entity. Odontogenic tumors are comparatively rare, comprising about 1% of all jaw tumors.  Odontogenic tumors are subjected to geographical variation and in India, commonest being the ameloblastoma followed by adenomatoid odontogenic tumor in a study conducted by Sriram et al.  Hence it is of utmost important for the practitioner to have a sound knowledge over these lesions for better patient management.
Ameloblastoma is defined as "True neoplasm of enamel organ type tissue which does not undergo differentiation to the point of enamel formation." Clinically, Ameloblastoma is classified into solid multicystic, unicystic, desmoplastic, and peripheral variants. Of which the unicystic ameloblastoma is a unique cystic variant of ameloblastoma with clinical and radiological features that very closely resembles odontogenic cysts of developmental and inflammatory origin. Its uniqueness is attributed to its clinical behavior and a favorable prognosis rate, though the histologic section presents cells with neoplastic nature.
Literature reveals there is an incidence of 6-15% for the unicystic variant with an increased surge to involve individuals from second decade of life. There is a greater site predilection for mandibular ramus, followed by anterior mandible and maxilla. , Around 52-100% of unicystic ameloblastoma (UA) are associated with impacted tooth. The term "unicystic" is derived from its macro and microscopical appearances indicating single cystic sac lined by an odontogenic epithelium. Radiographically, it presents both unilocular and multilocular radiolucencies. 
UA showing unilocular radiolucencies associated with impacted tooth (dentigerous variant) affects younger individuals compared to UA showing multilocular radioluncencies without impacted tooth (non dentigerous variant).  Also studies reveal that there is a male predilection in dentigerous variant and female predilection in the non dentigerous variant. 
We herewith report a case of nondentigerous variant of unicystic ameloblastoma exhibiting diverse histopathological features.
| Case Report|| |
A 45-year-old female patient came to the Department of Oral and Maxillofacial Pathology, SRM Kattankulathur Dental College and Hospital with a complaint of a swelling in the left side of the mandible for past 2 years. The patient initially noticed a painless peanut sized swelling which was said to have grown to the current size.
Extra oral examination revealed a diffuse swelling in the left lower jaw with an extent from the right symphyseal to left molar region. Mild facial asymmetry was noticed. There were no palpable lymph nodes[Figure 1]. Intra orally, a fixed, non tender swelling scaling 4 x 5 cm was observed to extend from 42-36 regions, obliterating the buccal vestibule. The consistency was between firm to hard. The mucosa over the swelling was intact and there were no evidence of sinus opening or pus discharge [Figure 2]. All the teeth in the lesional area were vital and grade I mobility was recorded. Aspiration was positive. Computed tomography (CT) scan revealed a large multilocular radiolucent lesion with scalloped margins extending from 32-38 region, with thinned out buccal and lingual cortical plates [Figure 3]. A clinical diagnosis of odontogenic keratocyst/ameloblastoma was given. Incisional biopsy was done and reported as ameloblastic fibroma in a private diagnostic centre. Hemimandibulectomy was performed under general anesthesia and patient was advised for facial reconstruction. The resected specimen measured about 8 × 4 × 3 cm in size. Multiple sections were made from different regions of the resected specimen [Figure 4].
The microscopic examination of the hematoxylin and eosin stained section exhibited a large cystic cavity lined by an odontogenic epithelium of varying thickness satisfying the Vicker and Gorlin criteria. All the three patterns namely luminal, intraluminal, and mural invasion of follicular type were evident in the same section. Few of the follicles in the connective tissue stroma shows squamous metaplasia and also cystic degeneration similar to conventional multicystic ameloblastoma[Figure 5],[Figure 6],[Figure 7]. A final diagnosis of UA type 1.2.3 (that includes luminal, intraluminal, and mural variants) was made. Till now no recurrence has been seen and patient is still regularly being followed-up.
|Figure 1: Extraoral examination reveals a diffuse swelling in the left side symphyseal region|
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|Figure 2: Intraoral examination revealed a diffuse swelling in the left side of the anterior mandible obliterating the buccal vestibular region involving the incisors and premolars|
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|Figure 3: Axial view of computed tomography at the occlusal level shows multilocular radiolucent lesion involving the left side body of the mandible and thinning of both buccal and lingual cortices|
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|Figure 5: Section showing luminal proliferation with few odontogenic epithelial rests in the capsule. (H & E, 10×)|
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|Figure 6: section showing intraluminal proliferation of ameloblastic epithelium. (H & E, 10×)|
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|Figure 7: Thin cystic odontogenic epithelium lining the lumen with few ameloblastic follicles (mural type) and numerous bony trabeculae in the fibrocellular capsule (H & E, 4×). Inset: H & E, 40×. Depicts an Ameloblastic follicle|
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| Discussion|| |
Ameloblastoma is a benign epithelial odontogenic neoplasm that arises from the tooth forming apparatus. It was Robinson and Martinez in 1977, introduced the concept of UA. The term unicystic is derived from its clinical, radiological, gross, and microscopical appearances representing monocystic cavity with an ameloblastomatous epithelium either focally or entirely lining the lumen.
The mean age of occurrence was found to be 19 and 33 years for the dentigerous unilocular and nondentigerous multilocular UA respectively. , Dentigerous variant of UA often is associated with an impacted tooth mimicking the dentigerous and other developmental odontogenic cysts. Being locally aggressive and nonresponsive to the tooth extraction or the root canal treatment makes this entity to need a special concern.  Thus it is mandatory to submit all the tissue specimen that was recovered at the time of surgery for histopathological examination.
The genesis of this particular variant is still unclear; as it is of proposed to have de novo origin, arising from the preexisting odontogenic cysts, and or cystic degeneration of solid multicystic ameloblastoma. In the present case, the presence of cystic degeneration of follicles suggests origin from an existing multicystic conventional ameloblastoma. Apart from the cystic degeneration, few follicular cells exhibit squamous metaplasia.
The clinical behavior of UA is distinct from the other types as it poses a favorable prognosis and hence happens to be an incidental finding on routine radiographs.  Based on their nature and extent of tumor cells within the cyst wall, UA are categorized histopathologically by Ackermann et al., in 1988 into three types, type 1 represents simple cystic/luminal, type 2 representing intraluminal, and type 3 being the mural variant. Biological behavior varies between these variants.  Features of all the three hisopathological types of UA were evident in our case.
More recently Philipsen and Reichart  made some modifications in the classification proposed by Ackermann et al., considering:
- Subgroup 1: Luminal UA
- Subgroup 1.2: Luminal and intraluminal
- Subgroup 1.2.3: Luminal, intraluminal, and intramural
- Subgroup 1.3: Luminal and intramural
This classification will be handful for the clinician as far as the patient management is concerned. The first two subgroups can be treated effectively by some conservative approaches including the simple enucleation. The other two, however, should be treated like a conventional solid multicystic ameloblastoma with marginal or segmental resections. The use of Carnoy's solution during the procedure, as an additional measure to minimize the chance of recurrence should be performed cautiously as it poses some damage to the periodontium of the adjacent tooth.  The use of liquid nitrogen cryotherapy over these lesions poses success with minimal recurrence rate, but its role is still questionable.
| Conclusion|| |
The diagnosis of UA was based on clinical, radiological and histopathological features. UA especially the mural variant has strong propensity for recurrence. The true behavior, whatever the type of lesion may be defined clearly upon grossing and microscopic examination of the resected tissue. Hence, pathologists should emphasize the surgeons and clinicians to plan the treatment upon the final diagnosis to have a better prognosis
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]