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Unicystic ameloblastoma of the mandible - an unusual case report and review of literature
Rakesh S Ramesh*, Suraj Manjunath, Tanveer H Ustad, Saira Pais, K Shivakumar
Ameloblastoma is a true neoplasm of odontogenic epithelial origin. It is the second most common odontogenic neoplasm, and only odontoma outnumbers it in reported frequency of occurrence. Its incidence, combined with its clinical behavior, makes ameloblastoma the most significant odontogenic neoplasm. Unicystic ameloblastoma (UA) refers to those cystic lesions that show clinical, radiographic, or gross features of a mandibular cyst, but on histolo- gic examination show a typical ameloblastomatous epithelium lining part of the cyst cavity, with or without lumi- nal and/or mural tumor growth. It accounts for 5-15% of all intraosseous ameloblastomas. We report a case of unicystic ameloblastoma in a 30-year-old female, and review the literature.
Many benign lesions cause mandibular swellings, and these can be divided into those of odontogenic and nono- dontogenic origin. Lesions include ameloblastoma, radi- cular cyst, dentigerous cyst, keratocystic odontogenic tumour, central giant cell granuloma, fibro-osseous lesions and osteomas . The most common tumour of odontogenic origin is ameloblastoma, which develops from epithelial cellular elements and dental tissues in their various phases of development. It is a slow-growing, persistent, and locally aggressive neoplasm of epithelial origin. Its peak incidence is in the 3rd to 4th decades of life and has an equal sex distribution. It is often asso- ciated with an unerupted third molar . It may be detected during the course of routine radiography.
The vast majority of ameloblastomas arise in the mandible, and the majority of these are found in the angle and ramus region. There are three forms of ame- loblastomas, namely multicystic, peripheral, and unicys- tic tumors . Multicystic ameloblastoma is the most common variety and represents 86% of cases. Peripheral tumors are odontogenic tumors, with the histological characteristics of intraosseous ameloblastoma that occur solely in the soft tissues covering the tooth-bearing parts of the jaws. Unicystic tumors include those that have been variously referred to as mural ameloblasto- mas, luminal ameloblastomas, and ameloblastomas
arising in dentigerous cysts . The goal of treatment ameloblastoma is to achieve complete excision and appropriate reconstruction. We present a case of a large unicystic mandibular ameloblastoma in a 30 year old female.
A 30 year old lady presented with a slowly growing swelling on the right side of the face since one year (Fig- ure 1). There was no associated pain, difficulty in open- ing the mouth, chewing or articulating. On physical examination, there was a hard non-tender mass, mea- suring 8 cm by 5 cm arising from the right side of the mandible, involving the ramus, angle and body upto the right lower 1st premolar tooth. The oral mucosa was normal. No neck nodes were palpable. Systemic exami- nation was normal. An orthopantomogram (OPG) was done, which showed large cystic lesion in the right side of mandible (Figure 2). CT scan showed that the cystic lesion was confined to the mandible, with a thinned out cortex (Figure 3). The patient was taken up for surgery under general anaesthesia. A segmental mandibulectomy was done via a lip split incision (Figures 4, 5), and pri- mary closure achieved. The resected specimen had his- topathologic features consistent with unilocular ameloblastoma (Figure 6).
Unilocular ameloblastoma (UA) is a rare type of amelo- blastoma, accounting for about 6% of ameloblastomas. It
* Correspondence: email@example.com
Department of Surgical Oncology, St Johns Medical College Hospital, Sarjapur Road, Bangalore 560034, India
Ramesh et al. Head Neck Oncology 2010, 2:1 http://www.headandneckoncology.org/content/2/1/1
© 2010 Ramesh et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
usually occurs in a younger age group, with about 50%
of the cases occurring in the second decade of life.
More than 90% are located in the mandible [5-7].
Between 50 and 80% of cases are associated with tooth impaction, the mandibular third molar being most often involved. The‘dentigerous’ type occurs 8 years earlier on average than the ‘non-dentigerous’ variant. Patients most commonly present with swelling and facial asym- metry, pain being an occasional presenting symptom.
Mucosal ulceration is rare, but may be caused by
continued growth of the tumor. Small lesions are some- times discovered more on routine radiographic screen- ing examinations or as a result of local effects (like tooth mobility, occlusal alterations and failure of erup- tion of teeth) produced by the tumor . Histologically, the minimum criterion for diagnosing a lesion as UA is the demonstration of a single cystic sac lined by odonto- genic (ameloblastomatous) epithelium often seen only in focal areas. UA should be differentiated from odonto- genic cysts because the former has a higher rate of
Figure 1 Swelling right side of face.
Figure 2 OPG showing cystic lesion.
recurrence than the latter . In a clinicopathologic study of 57 cases of unicystic ameloblastoma, Acker- mann  classified this entity into the following three histologic groups:
Group I: Luminal UA (tumor confined to the lumi- nal surface of the cyst)
Group II: Intraluminal/plexiform UA (nodular prolif- eration into the lumen without infiltration of tumor cells into the connective tissue wall), and
Group III: Mural UA (invasive islands of ameloblas- tomatous epithelium in the connective tissue wall not involving the entire epithelium).
Another histologic subgrouping by Philipsen and Reichart  has also been described:
Subgroup 1: Luminal UA
Subgroup 1.2: Luminal and intraluminal
Subgroup 1.2.3: Luminal, intraluminal and intramural Subgroup 1.3: Luminal and intramural
Figure 3 CT scan showing lesion in right hemimandible.
Figure 4 Lip split approach - mandibotomy.
Ramesh et al. Head Neck Oncology 2010, 2:1 http://www.headandneckoncology.org/content/2/1/1
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The UAs diagnosed as subgroups 1 and 1.2 can be treated conservatively (careful enucleation), whereas subgroups 1.2.3 and 1.3 showing intramural growths require treated radical resection, as for a solid or multi- cystic ameloblastoma . Following enucleation, vigor- ous curettage of the bone should be avoided as it may implant foci of ameloblastoma more deeply into bone.
Chemical cauterization with Carnoy’s solution is also
advocated for subgroups 1 and 1.2. Subgroups 1.2.3 and 1.3 have a high risk for recurrence, requiring more aggressive surgical procedures. This is because the cystic wall in these cases has islands of ameloblastoma tumor cells and there may be penetration into the surrounding cancellous bone [10-12]. Late recurrence following treat- ment is commonly seen, the average interval for recur- rence being 7 years. Recurrence is also related to
Figure 5 Resection complete.
Figure 6 Resected specimen.
histologic subtypes of UA, with those invading the fibrous wall having a rate of 35.7%, but others only 6.7%
. Recurrence rates are also related to the type of initial treatment. Lau et al  reported recurrence rates of 3.6% for resection, 30.5% for enucleation alone, 16% for enucleation followed by Carnoy’s solution appli- cation, and 18% by marsupialization followed by enu- cleation (where the lesion reduced in size).
Conflict of interests
The authors declare that they have no competing interests.
Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.
The authors are grateful to Dr. Arun Shet for review of the manuscript.
RSR participated in the surgical excision and drafted the manuscript SM conceived the study and participated in drafting manuscript and co- ordination
THU obtained consent and photographs and participated in the literature search
SP participated in surgical excision and in drafting manuscript SK performed the surgical excision and participated in literature search All authors read and approved the final manuscript.
Received: 1 November 2009
Accepted: 14 January 2010 Published: 14 January 2010
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Cite this article as: Ramesh et al.: Unicystic ameloblastoma of the mandible - an unusual case report and review of literature. Head & Neck Oncology 2010 2:1.
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