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 Table of Contents  
CASE REPORT
Year : 2018  |  Volume : 30  |  Issue : 2  |  Page : 169-172

Acanthomatous Ameloblastoma: A Rare Entity


1 Oral Medicine and Radiology, Kiran Dental Hospital, KPHB Colony, Hyderabad, India
2 Seattle's Union Gospel Mission Community Clinic, Seattle, Washington, USA
3 Department of Oral Medicine and Radiology, Mamata Dental College and Hospital, Khammam, Telangana, India
4 Faculty of Dentistry, AIMST Dental Institute, AIMST University, Semeling, Bedong, Malaysia

Date of Submission18-Jan-2018
Date of Acceptance17-Feb-2018
Date of Web Publication16-Jul-2018

Correspondence Address:
Dr. Kotya Naik Maloth
Department of Oral Medicine and Radiology, Mamata Dental College and Hospital, Khammam - 507 002, Telangana
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jiaomr.jiaomr_57_18

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   Abstract 


Ameloblastoma is a slow-growing and locally aggressive true neoplasm of enamel organ-type tissue which does not undergo differentiation to the point of enamel formation. It is most commonly seen in the posterior region of mandible, less commonly in anterior region, and rarely crossing the midline. It occurs in age ranging from 20 to 50 years with equal frequencies between sexes. It has a high recurrence rate due to its capacity to infiltrate marrow spaces with pseudopods without concomitant resorption of trabecular bone. As a result, the margins of the tumor are not clearly evident radiographically or grossly during operation, and the lesion frequently recurs after inadequate surgical removal. Here, we report a rare case of acanthomatous ameloblastoma present in a young male in the anterior mandibular region crossing the midline, along with an added emphasis on its review.

Keywords: Acanthomatous, ameloblastoma, mandible, neoplasm, tumor


How to cite this article:
Vallamchetla K, Chitty S, Maloth KN, Ugrappa S. Acanthomatous Ameloblastoma: A Rare Entity. J Indian Acad Oral Med Radiol 2018;30:169-72

How to cite this URL:
Vallamchetla K, Chitty S, Maloth KN, Ugrappa S. Acanthomatous Ameloblastoma: A Rare Entity. J Indian Acad Oral Med Radiol [serial online] 2018 [cited 2019 Jul 19];30:169-72. Available from: http://www.jiaomr.in/text.asp?2018/30/2/169/236733




   Introduction Top


Broca in 1868 was the first to report ameloblastoma, and the first detailed description was given by Falkson in 1879. Malassez in 1885 coined the term “adamantinoma,” implying the formation of hard tissue. Churchill in 1934 suggested an alternate name called “ameloblastoma.”[1] In 1977, Robinson defined ameloblastoma as, “it is usually unicentric, nonfunctional, intermittent in growth, anatomically benign and clinically persistent.” The World Health Organization (1991) defined ameloblastoma as a benign but locally aggressive tumor with a high tendency to recur, consisting of proliferating odontogenic epithelium lying in a fibrous stroma.[2] Ameloblastoma is most commonly seen in the posterior mandible but may also arise in the maxilla and anterior aspect of the jaws. The radiographic appearance ranges from a unilocular to a multilocular radiolucency, soap bubble, and honey comb appearance. There are also four different macroscopic subtypes: solid or multicystic, unicystic, desmoplastic, and peripheral.[3] This classification may have a prognostic value.[4] There are six histologic subtypes of ameloblastoma: follicular, plexiform, acanthomatous, granular, basal cell, and desmoplastic.[1],[4],[5] They can be found combined or isolated and that are not related to prognosis of the tumor. But according to Gumgum and Hogoren, the plexiform pattern is less aggressive and has a significantly lower recurrence rate.[6] Ameloblastomas rarely metastasize.[7]


   Case Report Top


An 18-year-old male patient reported to the department with complaint of swelling in his lower front teeth region for 4 months. The swelling had gradually increased in size and attained the present size. He gave no history of pain, paresthesia, discharge, fever, trauma, and loss of appetite. On extraoral examination, a diffuse swelling of size approximately 5 × 4 cm was present in the lower one-third of the face extending from left to the right corner of the mouth mesiodistally and from lower lip to the inferior border of the mandible and extending beyond it by 1 cm superioinferiorly, with obliteration of the lower mentolabial sulcus [Figure 1]a. On palpation, the swelling was nontender and soft in consistency. Crepitus was felt in the right and left corners of the chin. On intraoral examination, there was a diffuse swelling of size 5 × 2 × 2 cm extending from mesial of 36 to mesial of 46 crossing the midline, mesiodistally, and superioinferiorly from the marginal gingiva of 34, 33, 32, 31, 41, 42, and 43 to the depth of labial vestibule and alveolingual vestibule on the labial and lingual sides, respectively, and anterioposteriorly totally about 2 cm in relation to the lower anterior teeth. On palpation, it was soft in consistency and crepitus was felt in relation to 35, 34, 33, 32, 42, 43, and 44. No palpable pulsations were felt and no discharge was seen. Teeth 31, 41, and 42 showed pathological migration [Figure 1]b. Chair side investigations were performed; pulp vitality test showed no response for 34, 33, 43, and 44, while delayed response for 35 and 45. On needle aspiration, 2 mL of clear yellowish fluid was aspirated. Hence, provisional diagnosis was given as radicular cyst in relation to 35–45 with a differential diagnosis of ameloblastoma, odontogenic keratocyst, odontogenic myxoma, central giant cell granuloma, aneurysmal bone cyst, and traumatic bone cyst was considered.
Figure 1: Profile picture reveals a diffuse swelling at chin region (a); intraoral picture reveals obliteration of labial vestibule (b)

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Routine hematological investigation was performed which was non-contributory. Mandibular topographic [Figure 2] view revealed labiolingual expansion of the mandibular cortical plates with multilocular radiolucency. Panoramic radiograph [Figure 3] revealed a well-defined, corticated multilocular radiolucency centered on the lower anterior extending from mesial of 36 to mesial of 46 with root resorption in 34, 33, 32, 31, 41, and 42. There was thinning of the inferior mandibular border. Computed tomography scan was suggestive of a lytic expansile multilocular lesion [Figure 4]. Incisional biopsy was performed which revealed numerous epithelial cell nests present in connective tissue stroma. At the periphery, the follicle was lined by a single layer of tall columnar ameloblast-like cells with reverse polarity. Center island showed loosely arranged polygonal or angular cells resembling stellate reticulum; some follicles showed cystic degeneration of central stellate reticulum-like cells. Many follicles showed squamous metaplasia, suggestive of acanthomatous ameloblastoma [Figure 5]. Thus, on clinical, radiographical, and histopathological findings, final diagnosis given of acanthomatous ameloblastoma was made [Figure 5]. Extraction of the respective teeth and surgical enucleation were done. The patient is under follow-up since 2 years with no evidence of recurrence [Figure 6].
Figure 2: Mandibular topographic view reveals labiolingual expansion of the mandibular cortical plates with multilocular radiolucency

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Figure 3: Panoramic radiograph reveals a well-defined, corticated multilocular radiolucency with thinning of the inferior mandibular border

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Figure 4: Computed tomography reveals a lytic expansile multilocular lesion

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Figure 5: Histopathology picture reveals squamous metaplasia with keratin formation within the epithelial islands

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Figure 6: Postoperative pictures: (a) intraoral and (b) panoramic radiograph

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   Discussion Top


Ameloblastoma is a true neoplasm of odontogenic epithelium. It accounts for 1% of all tumors of the jaw encountered during the third to fifth decades of life. It is uncommon in children; in a review of 1,036 ameloblastoma of jaw, the average patient age is 38.9 years, with only 2.2% (19 of 858) under 10 years and 8.7% (75 of 858) between 10 and 19 years.[4]

About 80% of all cases occur in the mandible, of which 70% cases are seen in the ramus and in maxilla about 19%,[8] and rarely in anterior region. Ameloblastoma in the mandible can progress to great size and cause facial asymmetry, displacement of teeth, loose teeth, malocclusion, and pathologic fractures. Tumor size may range from 1 to 16 cm at presentation which results from expansion of bone and invasion into soft tissue.[9] Patients may present with a slow-growing mass, malocclusion, loose teeth, or more rarely paresthesia and pain; however, many lesions are detected incidentally on radiographic studies in asymptomatic patients.[10]

Radiographic features of most ameloblastoma cases showed an expansile, radiolucent, multiloculated cystic lesion, with a characteristic “soap bubble-like” appearance. Other findings also include cystic areas of low attenuation with scattered isoattenuating regions, representing soft-tissue components. Thinning and expansion of the cortical plate with erosion through the cortex can be seen. The associated unerupted tooth may be displaced and resorption of the roots of adjacent teeth is common.[10]

Various histological subtypes have been described, including those of follicular, plexiform, acanthomatous, granular, and basal cells. Most literatures showed that follicular ameloblastoma is the most prevalent histological variant (64.9%) followed by plexiform (13.0%), desmoplastic (5.2%), and acanthomatous (3.9%) varieties.[10] Histopathologically, acanthomatous type shows central squamous cell differential with keratin formation as seen in the present case. Some authors stated that formation of squamous metaplasia may be due to chronic irritation of calculus and oral sepsis.[8]

The location of acanthomatous ameloblastoma is considered to be rare and uncommon and more commonly appearing in the mandible (81%) than the maxilla (19%). In maxilla, the lesion found most were in the molar area (47%), antrum, and nasal floor (33%). Of the many types encountered, acanthomatous ameloblastoma is a very rare variant. On the basis of some previous cases, it was reported that acanthomatous ameloblastoma usually occurs in older individual rather than younger ones,[8] whereas in our case it is a young male patient.

Some authorities believe that acanthomatous ameloblastoma if left untreated can develop into an invading squamous cell carcinoma.[11] It is important to note in these circumstances that metaplasia of the odontogenic epithelium toward the squamous cell type in acanthomatous ameloblastoma can simulate the appearance of both a squamous cell carcinoma and a basal cell carcinoma. The histologic resemblance between different types of ameloblastoma, on one hand, and squamous cell carcinoma and basal cell carcinoma, on the other, has led to some erroneous diagnoses, and Lucas stated that this probably accounts for some reports of metastasizing ameloblastoma. Although histological features of acanthomatous ameloblastoma are different, it is now believed to be identical to the other types of ameloblastoma with no special extensive local infiltration and bone destruction or risk of recurrence.[8],[11]

There are controversies about the biological behavior of acanthomatous ameloblastoma; some authors believe that it is locally aggressive and frequently invades the alveolar bone or recurs after marginal surgical excision and some others believe that there is no difference among the various subtypes of ameloblastoma.[11] Thus, the study of molecular mechanisms of cell proliferation can be helpful to predict the aggressiveness of ameloblastoma and especially p16 (cyclin-dependent kinase inhibitor) which is a tumoral suppressor protein encoded by CDKN2A gene. A high score in immunoexpression of the p16 protein may indicate lower aggressiveness and a lower rate of recurrence.[12]

Treatment decisions for ameloblastoma are based on an individual patient's situation and the best judgment of a surgeon. Surgical plan should be influenced strongly by clinicoradiologic variant, anatomic location, clinical behavior, size of the tumor, and age of the patient. Radical treatment alters facial esthetics, maxilla–mandibular harmony, and social life of a patient.

But the mainstay of treatment is surgery, with wide resection recommended due to high recurrence rate of solid/multicystic ameloblastomas. The recurrence rate after resection is 13%–15%, as opposed to 90%–100% after curettage. Many authors recommend a margin of 1.5–2 cm beyond the radiological limit to ensure all microcysts are removed.[13]


   Conclusion Top


In conclusion, the present case has some interesting unusual features which can be distinguished from the other reported cases of ameloblastoma. First, this is a case of acanthomatous ameloblastoma which is one of a rare variant of ameloblastoma. Second, the common age group of ameloblastoma is from 20 to 50 years, whereas in this case it is less than 20 years of age. Third, the common site is posterior ramus of mandible, whereas it is in the anterior region of the mandible. Fourth, in young individuals, ameloblastoma usually is associated with impacted tooth, whereas in the present case it is not. Considering various studies, a conservative approach was used in this patient, rather than a radical approach. The patient is under follow-up since 2 years with no evidence of recurrence.

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.
Churchill HR. Histological differentiation between certain dentigerous cysts and ameloblastoma. Dent Cosmos 1934;76;1173-8.  Back to cited text no. 1
    
2.
Kramer IRH, Pindborg JJ, Shear M. Histological typing of odontogenic tumours. WHO International Histological Classification of Tumours. 2nd edition. Berlin: Springer-Verlag; 1992. p. 11-4.  Back to cited text no. 2
    
3.
Reichart PA, Philipsen HP, Sonner S. Ameloblastoma: Biological profile of 3677 cases. Eur J Cancer 1995;31:86-99.  Back to cited text no. 3
    
4.
Gardner DG, Morton TH, Worsham JC. Plexiform unicystic ameloblastoma of the maxilla. Oral Surg Oral Med Oral Pathol 1987;63:221-3.  Back to cited text no. 4
    
5.
Shafer WG, Hine MK, Levy BM. A Textbook of Oral Pathology. 4th edn. Philadelphia: Saunders; 1983. p. 276-85.  Back to cited text no. 5
    
6.
Gumgum S, Hogoren B. Clinical and radiologic behaviour of ameloblastoma in 4 cases. J Can Dent Assoc 2005;71:481-4.  Back to cited text no. 6
    
7.
Madiedo GH, Choi RL, Kleinman MP, Cuninham GP. Ameloblastoma with distant metastases and hypercalcemia. Am J Clin Path 1981;75:585-91.  Back to cited text no. 7
    
8.
Bansal M, Chaturvedi TP. Acanthomathous ameloblastoma of anterior maxilla. J Indian Pedodontic Soc Prev Dent 2010:3:28:209-11.  Back to cited text no. 8
    
9.
Kahairi A, Ahmad RL, Wan Islah L, Norra H. Management of large mandibular ameloblastoma – A case report and literature reviews. Arch Orofac Sci 2008;3:52-5.  Back to cited text no. 9
    
10.
Bhargava A, Saigal S, Chalishazar M. Acanthomatous ameloblastoma of mandible. J Dent Sci Res 2011;2:1-5.  Back to cited text no. 10
    
11.
Anneroth G, Anders H, Jan W. Acanthomatous ameloblastoma. Int J Oral Surg 1980;9:231-6.  Back to cited text no. 11
    
12.
Olimid DA, Florescu AM, Cernea D, Georgescu CC, Margaritescu C, Simionescu CE, et al. The evaluation of p16 and Ki67 immunoexpression in ameloblastomas. Rom J Morphol Embryol 2014;55:363-7.  Back to cited text no. 12
    
13.
Hong J, Yun PY, Chung IH, Myoung H, Suh JD, Seo BM, et al. Long-term follow up on recurrence of 305 ameloblastoma cases. Int J Oral Maxillofac Surg 2007;36:283-8.  Back to cited text no. 13
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]



 

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