Unicystic Ameloblastoma: A Case Report and 4 Years Follow Up

Antoine Berberi *¹, Georges Aad ², Albert Waked ³, Agness Risk ⁴, Nabih Nader ⁵

1. BDS, MSc, PhD, HDR. Professor, Head Department of Oral and Maxillofacial Surgery, Faculty of Dental Medicine, Lebanese University.

2. BDS, DU. Clinical Assistant, Department of Oral Medicine and Maxillofacial Radiology, Faculty of Dental Medicine, Lebanese University.

3. BDS, MSc, Department of Oral and Maxillofacial Surgery, Faculty of Dental Medicine, Lebanese University.

4. BDS, Lebanese University.

5. BDS, CES, DU, Clinical Assistant Professor and Director of the Oral Surgery Master Program, Department of Oral and Maxillofacial Surgery, Faculty of Dental Medicine, Lebanese University.

Corresponding Author: Berberi Antoine, Department of Oral and Maxillofacial Surgery, Dental Faculty, Lebanese University.

Copy Right: © 2023 Berberi Antoine, This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Received Date: January 30, 2023

Published Date: February 10, 2023

DOI: 10.1027/mards.2023.0347

Abstract

Ameloblastoma is an invasive tumor which originates from remnants of the dental lamina and odontogenic epithelium and represents 1 % of all maxillary tumors.

A case of unicystic ameloblastoma and a conservative therapeutic attitude are reported with a four-year follow-up.

The importance of biopsy before surgical excision is underlined.

Keywords: Unicystic, ameloblastoma, impacted, molar, mandible.

Introduction

Ameloblastoma, odontogenic tumors of epithelial origin without induction of mesenchyme that represent 1 % of oral tumors, represent a very particular clinical and radiological entity [1, 2]. The World Health Organization (WHO) classified ameloblastoma in four types: multicystic, peripheral, desmoplastic and unicystic ameloblastomas [1, 2].

The topography of these tumors is variable. They are rarely observed at the level of the maxilla and are found at the level of the mandibular symphysis, but their most frequent situation is at the level of the mandibular angle and can invade the ascending ramus or even the coronoid process [3, 4].

Radiologically, ameloblastoma are described as a radiolucent, multilocular image leading to expansions, 90% of cases present a multilocular aspect and 10% are unilocular. They can be associated with impacted teeth and/or cause root resorption or tooth displacement [5, 6].

The differential diagnosis arises with dentigerous cysts [7]. This is why it is advisable to carry out the histopathological examination of all suspected cases of dentigerous cysts, especially to detect unicystic ameloblastoma, which form from their epithelial lining, without radiological signs indicating this significant variation [4, 8].

Unicystic ameloblastoma, a very rare variety, constitutes 5% of ameloblastoma [9].

Various studies have shown that 15 to 30% of all ameloblastoma form from the wall of a dentigerous cyst [6-8].

On the other hand, 85% of unicystic ameloblastoma are associated with observed dentigerous cysts, all in patients who have not exceeded the third decade [6, 7, 9].

Three histological types are recognizable according to the degree of ameloblastomatous epithelial extension, namely luminal, intraluminal, and mural types [4, 5].

Compared to solid and multi-cystic ameloblastoma, unicystic ameloblastoma are considered to be less aggressive and respond more favorably to conservative management [8, 10].

In this article we present a case of mural ameloblastoma with a conservative therapeutic attitude and a clinical and radiological follow-up of 4 years.

Clinical Case

A 16-year-old female consulted us for left an intra-oral swelling in the retro-molar region with absence of her second mandibular molar. (Figure 1).

Palpation reveals liquid contents of the swelling. Depressibility test indicates the presence of a thin osteo-periosteal shell opposite to the tumefaction. Endo-buccal examination reveals a fluctuating collection filling the bottom of the vestibule facing the mandibular premolars and molars. The wisdom tooth and the second molar were missing from the dental arch. The first molar as well as the second premolar were mobile and sensitive to percussion. No sign of right inferior alveolar nerve paresthesia.

A panoramic radiograph shows expansive unilocular radiolucency's with a well-demarcated margin extending from the right mandibular second premolar to the right ramus posteriorly. the right mandibular condyle is spared. The lesion caused the expansion of both vertical and horizontal branches with thinning of the basilar rim. From a dental point of view, there is no root resorption of the first mandibular molar, while the left mandibular second molar is included in the lesion and pushed anteriorly down to the root of the first molar and the third molar is also included in the lesion and pushed back towards the right mandibular angle. (Figure 2). The preliminary diagnosis was a dentigerous cyst, keratocyst or a type of ameloblastoma.

In order to decide the extension of the surgical act and the histological nature of the lesion; an incisional biopsy is decided under local analgesia.

The histological examination confirms the diagnosis of a mural ameloblastoma

Following the histological results, it was decided to perform a conservative excision surgery.

An intermaxillary arch retainer is placed preoperatively to prevent a possible fracture of the left mandibular angle and under local analgesia the tumor was excised and both molars removed (Figure. 3a, 3b and 3c).

A paresthesia of the right inferior alveolar nerve is observed postoperatively. She was a passenger.

Histopathological examination reveals the presence of a cystic wall on which are grafted colonies of ameloblasts outside the cystic cavity and highlights a polarization of the basal cells with a displacement of the nucleoli, hyperchromatism and vacuolation of the cytoplasm, which confirms the diagnosis of a cystic ameloblastoma. (Figure 4).

One week later a clinical healing was observed and the control X-ray shows bone healing well underway. (Figure. 5a and 5b).

One month later, the clinical exam and the panoramic X-ray reveals a good healing process and the intermaxillary arch was removed. (Figure. 6a and 6b).

One year later the panoramic X-ray reveal a complete bone healing. (Figure 7).

Four years later the bone apposition is complete and the radiographic examination shows no recurrency. (Figure 8)

Discussion

Ameloblastoma are subdivided into 2 biological/microscopic subtypes:

solid or multilocular ameloblastoma and unicystic ameloblastoma [3,4].

There is a very significant rationale for such a subdivision as treatment and prognosis differ [10]. Solid ameloblastoma is more aggressive and requires more radical treatment than cystic ameloblastoma and shows a high rate of recurrence (50-90%) if treated by curettage [8, 10]. Unicystic ameloblastoma, on the other hand, is an ameloblastoma that has a wide cystic space in which there can be wall growth [5, 9].

It could represent a cystic ameloblastoma which is unilocular or, an odontogenic cyst in which there have been ameloblastic transformations at the level of the epithelial wall [7, 9].  A histological variant of this type is cystic plexiform ameloblastoma in which the cyst wall shows a network of ameloblastic epithelium [11].

Unicystic ameloblastoma are rare and constitute about 10% of all ameloblastoma: which usually are observed in young population with an average of 22 years [9]. They are characterized by slow growth and being moderately aggressive, with the highest localization in the posterior part of the mandible [12, 13].

Radiographically, the lesions usually show expansive unilocular radiolucency's with a well-delimited margin. Around 50–80% of cases are allied with an impacted or unerupted tooth [9,12].

Thus, the clinical and radiographic appearances of unicystic ameloblastoma are in some cases indistinguishable from those of dentigerous cysts [9, 13].

The categorization of unicystic ameloblastoma cannot be made only on the radiological appearance, histological detecting of ameloblastic cells infiltration of the cystic wall or extramural proliferation should be performed [9, 12, 13].

Unicystic ameloblastoma may show a variable, plexiform or follicular epithelial wall, frequently with typically ameloblastic cells in the basal layer in several places. The wall of the cystic area becomes flattened and although a few ameloblastic cells may be seen, it may resemble that of a non-neoplastic cyst [9,13].

Conclusion

The incisional biopsy substantiated to be essential in the choice of our therapeutic attitude. It limited the extent of our surgical excision; which spared our patient a hemi mandibulectomy. The long term follow-up is essential to control bone healing.

Reference

1. Sivapathasundharam B, Biswas PG, Preethi S. The World Health Organization classification of odontogenic and maxillofacial bone tumors: An appraisal. J Oral Maxillofac Pathol. 2019 May-Aug;23(2):178-186. doi: 10.4103/jomfp.JOMFP_211_19. PMID: 31516220; PMCID: PMC6714253.2.

2. Vered M, Wright JM. Update from the 5th Edition of the World Health Organization Classification of Head and Neck Tumors: Odontogenic and Maxillofacial Bone Tumours. Head Neck Pathol. 2022 Mar;16(1):63-75. doi: 10.1007/s12105-021-01404-7. Epub 2022 Mar 21. PMID: 35312978; PMCID: PMC9019005.3

3. Kreppel M, Zöller J. Ameloblastoma-Clinical, radiological, and therapeutic findings. Oral Dis. 2018 Mar;24(1-2):63-66. doi: 10.1111/odi.12702. PMID: 29480593.4

4. Evangelou Z, Zarachi A, Dumollard JM, Peoc'h M, Komnos I, Kastanioudakis I, Karpathiou G. Maxillary Ameloblastoma: A Review With Clinical, Histological and Prognostic Data of a Rare Tumor. In Vivo. 2020 Sep-Oct;34(5):2249-2258. doi: 10.21873/invivo.12035. PMID: 32871747; PMCID: PMC7652510.

5. Arora S. Unicystic Ameloblastoma: A Perception for the Cautious Interpretation of Radiographic and Histological Findings. J Coll Physicians Surg Pak. 2015 Oct;25(10):761764-764. doi: 10.2015/JCPSP.761764. PMID: 26454399.

6. Alves DBM, Tuji FM, Alves FA, Rocha AC, Santos-Silva ARD, Vargas PA, Lopes MA. Evaluation of mandibular odontogenic keratocyst and ameloblastoma by panoramic radiograph and computed tomography. Dentomaxillofac Radiol. 2018 Oct;47(7):20170288. doi: 10.1259/dmfr.20170288. Epub 2018 Jun 5. PMID: 29791200; PMCID: PMC6196060.

7. Barrett AW, Sneddon KJ, Tighe JV, Gulati A, Newman L, Collyer J, Norris PM, Coombes DM, Shelley MJ, Bisase BS, Liebmann RD. Dentigerous Cyst and Ameloblastoma of the Jaws. Int J Surg Pathol. 2017 Apr;25(2):141-147. doi: 10.1177/1066896916666319. Epub 2016 Sep 24. PMID: 27621276.

8. Effiom OA, Ogundana OM, Akinshipo AO, Akintoye SO. Ameloblastoma: current etiopathological concepts and management. Oral Dis. 2018 Apr;24(3):307-316. doi: 10.1111/odi.12646. Epub 2017 Mar 9. PMID: 28142213.

9. Panneerselvam K, Kavitha B, Panneerselvam E, Parameswaran A. Mural Unicystic Ameloblastoma mimicking Odontogenic Cyst. J Family Med Prim Care. 2020 May 31;9(5):2524-2527. doi: 10.4103/jfmpc.jfmpc_178_20. PMID: 32754536; PMCID: PMC7380812.

10. Hendra FN, Natsir Kalla DS, Van Cann EM, de Vet HCW, Helder MN, Forouzanfar T. Radical vs conservative treatment of intraosseous ameloblastoma: Systematic review and meta-analysis. Oral Dis. 2019 Oct;25(7):1683-1696. doi: 10.1111/odi.13014. Epub 2019 Jan 1. PMID: 30548549.

11. Deore SS, Dandekar RC, Mahajan AM, Patil R, Prakash N. Plexiform unicystic ameloblastoma: a rare variant of ameloblastoma. Case Rep Dent. 2014;2014:146989. doi: 10.1155/2014/146989. Epub 2014 Aug 14. PMID: 25202458; PMCID: PMC4150428.

12. Kalmegh PP, Hande AH, Gawande MN, Patil SK, Sonone AM. Unicystic Ameloblastoma (UA): A Case Series. Cureus. 2022 Nov 3;14(11):e31039. doi: 10.7759/cureus.31039. PMID: 36475180; PMCID: PMC9719033.

13. da Silva YS, Sohal KS, Stoelinga PJW, Grillo R. A meta-analysis on the presentation of Unicystic Ameloblastoma in the jaws and the consequences for their treatment. J Stomatol Oral Maxillofac Surg. 2022 Oct;123(5):e433-e438. doi: 10.1016/j.jormas.2022.01.004. Epub 2022 Jan 10. PMID: 35017129.