Abstract
Ameloblastoma is a true neoplasm of odontogenic epithelial origin. It is the second most common odontogenic neoplasm and only odontoma out numbers it. The tumor is often asymptomatic presenting as slowly enlarging facial swelling or an incidental finding on a radiograph. The physical presence of the tumor may cause symptoms such as pain, ulceration, loosening of teeth or malocclusion. Ameloblastoma is a locally destructive tumor with a propensity for recurrence if not entirely excised. A few cases of malignant change with distant metastasis have been reported in the literature. The treatment of ameloblastoma is still controversial. Unicystic ameloblastoma refers to those cystic lesions that show clinical, radiographic features of a cyst, but on histological examination show a typical ameloblastomatous epithelium. We report a case of unicystic ameloblastoma in the mandible unusual presentation, with review of literature. Key words: Ameloblastoma, odontogenic neoplasm, Unicystic ameloblastoma.

Introduction
According to the WHO 1992 definition, ameloblastoma is a benign but locally invasive polymorphic neoplasm consisting of proliferating odontogenic epithelium, which usually has a follicular or plexiform pattern, lying in a fibrous stroma. WHO histological typing of odontogenic tumors classifies ameloblastoma as intraosseous central, and extra-osseous peripheral types1, the small number of ameloblastomas arising directly from the surface epithelium or from residues of the dental lamina lying outside the bone constitute the peripheral type. The intraosseous ameloblastoma of the jaws occurs most often in the fourth and fifth decades of life. In more than 90% of the cases, the unicystic ameloblastoma is located in the mandible, with 77% located in the molar ramus region2.

Ameloblastoma, theoretically, may arise from the cell rests of the enamel organ, from a developing enamel organ, from the epithelial lining of an odontogenic cyst, or from the basal cells of the oral mucosa3,4. Regezi and Sciubba reported that ameloblastoma accounts for 11% of all odontogenic tumors in the jaw5. The clinicopathological features are benign with a slow growing pattern, but locally invasive. The clinical behaviour may be regarded as lying somewhere between benign and malignant. Radiographic appearances of the early stages of ameloblastoma are not characteristic, a local area of bone destruction of cyst like, often unilocular appearance. In its later stages ameloblastoma presents an expansile lesion with multilocular, rounded radiolucencies. Various treatment methods for the lesion in relation to many factors, such as the tumour size and location, have been suggested. These include enucleation, marginal resection and aggressive resection. When a diagnosis of ameloblastoma is obtained, the treatment must be aggressive and radical. This concurs with the opinion that a resection of the jaw should be approximately 1.5–2 cm beyond the radiological limit. Recurrence following treatment is commonly seen, the average interval for recurrence being 7 years6,7.

Case Report
A 27 year female patient (Fig-1,2) reported to the clinics with a chief complaint of pain in the right lower back region since 2 years with history of extraction of the right lower wisdom tooth 2 years prior, since then the patient had mild and continuous pain. Clinical examination revealed soft brownish ulcerated mass on the right retromolar region, non tender and soft to firm in consistency. No expansion of the buccal or lingual cortical plates was noticed. Past dental and medical history were unremarkable, with no other abnormality on physical examination. Panoramic radiograph revealed 48 missing with large unilocular radiolucency distal to 47 extending superiorly and distally in to the ramus of the mandible with definite margins. A provisional diagnosis of giant cell lesion or odontogenic keratocyst was made and incisional biopsy was performed. Biopsy report from reputed histopathology department was reported as Chronic non-specific inflammation. However enucleation of the lesion was performed to completely extirpate the lesion. The resulting histopalthlogic diagnosis from two sources supportive of unicystic ameloblastoma.

Discussion
Unicystic ameloblastoma, a variant of ameloblastoma first described by Robinson and Martinez in 1977, refers to those cystic lesions that show clinical and radiologic characteristics of an odontogenic cyst but on histological examination show a typical ameloblastomatous epithelium lining part of the cyst cavity, with or without luminal and/or mural tumor proliferation8,9. Unicystic ameloblastoma is a rare type of ameloblastoma, accounting for about 6% of ameloblastomas. It usually occurs in a younger age group, with about 50% of the cases occurring in the second decade of life10. More than 90% are located in the mandible. Between 50 and 80% of cases are associated with tooth impaction, the mandibular third molar being most often involved, with swelling and facial asymmetry, pain being an occasional presenting symptom11. Mucosal ulceration is rare, but may be caused by continued growth of the tumor effects like tooth mobility, occlusal alterations and failure of eruption of teeth12. The above case reported was unusual clinical presentation with a soft non tender mass and the incisional biopsy report was non specific chronic inflammatory lesion. However, outcome of the lesion was unicystic ameloblastoma. Histologically, the minimum criterion for diagnosing a lesion as unicystic ameloblastoma is the demonstration of a single cystic sac lined by odontogenic (ameloblastomatous) epithelium often seen only in focal areas. Unicystic ameloblastoma should be differentiated from odontogenic cysts because the former has a higher rate of recurrence than the later. Ackermann classified this entity into the following three histologic groups:
Group I: Luminal UA (tumor confined to the luminal surface of the cyst)
Group II: Intraluminal/plexiform UA (nodular proliferation into the lumen without infiltration of tumor cells into the connective tissue wall), and
Group III: Mural UA (invasive islands of ameloblastomatous 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 intramural13
The unicystic ameloblastomas 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 multicystic ameloblastoma. Following enucleation, vigorous 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. Late recurrence following treatment is commonly seen, the average interval for recurrence being 7 years. 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 application, and 18% by marsupialization followed by enucleation14,15,16.
Conclusion
Unicystic ameloblastoma is a tumour with a strong propensity for recurrence, especially when the ameloblastic focus penetrates the adjacent tissue from the wall of the cyst. Often the clinical picture of the lesion is misleading as it was in the above case reported. This makes the clinician to consider unicystic ameloblastoma as one of the possibility. The ability to predict this potential occurrence prior to surgery would greatly enhance therapeutic strategies for reducing the incidence. References

1. Kramar IR, Pindborg JJ, Shear M. WHO international classification of tumours: histological typing of odontogenic tumours. Berlin: Springer-Verlag, 1992.

2. Ackermann GL, Altini M, Shear M: The unicy stic ameloblastoma: A clinicopathological study of 57 cases. J Oral Pathol 17:541, 1988

3. Leider AS, Eversole LR, Barkin ME: Cystic ameloblastoma: A clinico-pathologic analysis. Oral Surg Oral Med Oral Pathol 60:624, 1985.

4. Crawley WA, Levin LS. Treatment of the ameloblastoma: a controversy. Cancer 1978: 42: 357– 363

5. Williams TP. Management of ameloblastoma: a changing perspectiv e. J Oral Maxillof ac Surg 1993: 51: 1064– 1070.

6. Neville BW, Damm DD, Allen CM, Bouquot JE. Oral and Maxillofacial Pathology. Philadelphia: W. B. Saunders 1995: pp. 512–520.

7. Small IA, Waldron CA. Ameloblastomas of the jaws. J Oral Surg 1955: 8: 281– 297.

8. Takahashi K, Miyauchi K, Sato K. Treatment of ameloblastoma in children. Br J Oral Maxillofac Surg 1998;36:453-6.

9. Robinson L, Martinez MG. Unicystic ameloblastoma: A prognostically distinct entity. Cancer 1977;40:2278-85

10. Olaitan AA, Adekeye EO: Clinical features and management of ameloblastoma of the mandible in children and adolescents. Br J Oral Maxillofac Surg 34:248, 1996.

11. Reichart PA, Philipsen HP, Sonner S: Ameloblastoma: Biological profile of 3677 cases. Oral Oncol Eur J Cancer 31B:86, 1995.

12. Williams TP. Unicystic ameloblastoma- A case report of the mandible. J Oral Maxillof ac Surg 1997: 55(4): 345-348.

13. Rakesh S RAmesh, Suraj Manjunath, Tanveer H UStad, Saira Pais, K Shiva Kumar. Unicystic ameloblastoma of the mandible – an unusual case report and review of literature. Head Neck Oncology Jan 2010;2:1-4

14. Small IA, Waldron CA. Ameloblastomas of the jaws. J Oral Surg 1955: 8: 281– 297.

15. Olaitan AA, Adeola DS, Adekeye EO. Ameloblastoma: clinical features and management of 315 cases from Kaduna, Nigeria. J Craniomaxillofac Surg 1993: 21: 351–355.

16. Adek eye EO. Ameloblastoma of the jaws: a survey of 109 Nigerian patients. J Oral Surg 1980: 38: 36–41.


LEGENDS

1. Patient photo showing no gross asymmetry
2. Patient on profile view
3. Growth with ulceration on the right retromolar region
4. OPG showing radiolucency in the right ramus with missing 48
5. Incisional biopsy of the lesion
6. Specimen
7. Excisional biopsy of the lesion showing hallowing of the ramus
8. Post operative sutures in place

Fig-1

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