Journal of Dental and Allied Sciences

REVIEW ARTICLE
Year
: 2017  |  Volume : 6  |  Issue : 2  |  Page : 70--73

Ameloblastic carcinoma of the jaws: Review of the literature


Ramat Oyebunmi Braimah1, Chibuzo Uguru2, Kizito Chioma Ndukwe3,  
1 Department of Dental and Maxillofacial Surgery, Usmanu Danfodiyo University Teaching Hospital, Sokoto, Nigeria
2 Department of Oral and Maxillofacial Surgery, University of Nigeria, Enugu Campus, Enugu, Nigeria
3 Department of Oral and Maxillofacial Surgery and Oral Pathology, Obafemi Awolowo University Teaching Hospitals Complex, Ile-Ife, Osun State, Nigeria

Correspondence Address:
Dr. Ramat Oyebunmi Braimah
Department of Dental and Maxillofacial Surgery, Usmanu Danfodiyo University Teaching Hospital, Sokoto
Nigeria

Abstract

Ameloblastic carcinoma is a rare odontogenic malignancy that combines the histological features of ameloblastoma with cytological atypia, even in the absence of metastases. The major prognostic factor is the clinical course of the disease which includes its aggressiveness, local destruction, and distant metastatic spread preferentially through hematologic route if neglected. Histologically, ameloblastic carcinoma retains the features of ameloblastic differentiation and exhibits cytological features of malignancy in a primary or recurrent tumor. Because it is a very rare lesion, it poses a great difficulty in diagnosis. En bloc removal with 1–2 cm of normal bone margin has been regarded as the safest surgical modality to ensure disease-free survival. Literature search was carried out using the Boolean operator “And” between ameloblastoma and carcinoma on PubMed. Retrieved articles were extensively reviewed for epidemiology, etiology, diagnosis, treatment options, and prognosis of ameloblastic carcinoma.



How to cite this article:
Braimah RO, Uguru C, Ndukwe KC. Ameloblastic carcinoma of the jaws: Review of the literature.J Dent Allied Sci 2017;6:70-73


How to cite this URL:
Braimah RO, Uguru C, Ndukwe KC. Ameloblastic carcinoma of the jaws: Review of the literature. J Dent Allied Sci [serial online] 2017 [cited 2022 Jun 26 ];6:70-73
Available from: https://www.jdas.in/text.asp?2017/6/2/70/219978


Full Text



 Introduction



Ameloblastic carcinoma is a rare odontogenic tumor accounting for 1.5%–2.0% of all odontogenic tumors.[1] Only seventy cases have been reported in English literature from 1984 to 2011.[2] In 1982, the term “ameloblastic carcinoma” was introduced by Elzay[3] to depict a malignant epithelial odontogenic tumor that histologically retains the features of ameloblastic differentiation and exhibits cytological features of malignancy in a primary or recurrent tumor. In the last WHO classification update published in 2005, it is defined “as a rare odontogenic malignancy that combines the histological features of ameloblastoma with cytological atypia, even in the absence of metastases.”[2] It has characteristic histologic features and clinical behavior that requires a more aggressive surgery than that of ameloblastoma. Malignant ameloblastoma differs from ameloblastoma due to the presence of metastases, they both have the same benign histology.[4] Malignant ameloblastoma and ameloblastic carcinoma have been used interchangeably before in the past. However, it is now agreed that malignant ameloblastoma has the ability to metastasizes despite its benign histology in both the primary and the metastatic lesion.[5] On the other hand, ameloblastic carcinoma demonstrates histologic features of both ameloblastoma and carcinoma[3] with histologic features of malignancy found in both the primary and the metastases.[6]

Ordinarily, the tumor cells in ameloblastic carcinoma resemble the cells seen in ameloblastoma, however they show cytologic atypia. The tumor usually has direct extension, lymph node involvement, and metastasis to distant sites especially the lungs. Because it is a very rare lesion, it poses a great difficulty in diagnosis. Literature search was carried out using the Boolean operator “And” between ameloblastoma and carcinoma on PubMed. Retrieved articles were extensively reviewed for epidemiology, etiology, diagnosis, treatment options, and prognosis of ameloblastic carcinoma.

 Epidemiology



Ameloblastic carcinoma shows no age group predilection appears more frequently in men (two-third of cases) and involves more often the mandible (two-third of cases). According to Dhir et al.,[7] age range of the patients varies widely with a range of 51–84 years and a mean age of 53.5 years. No sex or race predilection has been noted;[8],[9] however, a male to female ratio ranging from 1.2:1 to 2.7:1[7],[10],[11] have been documented. Ramesh et al.[12] showed a contrary sex ratio of female:male to be 3:2 showing a female preponderance. It occurs primarily in the mandible in about 80% of cases reported.[7] Racial predilection of blacks over whites have also been reported.[13]

 Etiology



The etiology of ameloblastic carcinoma is largely unknown and still controversial.[11] Most cases arise spontaneously without a previous history of cancer (de novo) with few cases arising following malignant transformation of ameloblastoma.[14] Ndukwe et al.,[10] in a multicenter study of ameloblastic carcinoma in Nigerians reported that most of the cases (85%) arise de novo with only 15% presenting as carcinoma ex-ameloblastoma. Researchers speculate that genetic and immunologic abnormalities, environmental factors (e.g., exposure to ultraviolet rays, certain chemicals, ionizing radiation), diet, stress, and/or other factors may play contributing roles in causing specific types of cancer.[15] In individuals with cancer, malignancies may develop due to abnormal changes in the structure and orientation of oncogenes or tumor suppressor genes.[15] Oncogenes control cell growth while tumor suppressor genes control cell division and ensure that cells die at the proper time (apoptosis).[15] The specific cause of changes to these genes is, however, unknown. Conversely, current research suggests that abnormalities of deoxyribonucleic acid, which is the carrier of the body's genetic code, are the underlying basis of cellular malignant transformation.[15] These abnormal genetic changes may occur spontaneously for unknown reasons or, more rarely, may be inherited.[15] Hypermethylation of p16 gene have been reported to be involved in the malignant transformation of initial benign ameloblastoma to an ameloblastic carcinoma.[16] Ameloblastic carcinoma may develop from the epithelial tissue that remains after the development of the teeth and associated structures.[2] In some cases, it results from malignant transformation of an existing ameloblastoma or a benign odontogenic cyst.[14] Benlyazid et al.[2] have reaffirmed this position of ameloblastic carcinoma as arising de novo, or from odontogenic cyst, or from ameloblastoma. The majority have been said to originate de novo, and the remaining are malignant transformation of an odontogenic cyst or ameloblastoma.[17]

 Clinical Features



Unlike ameloblastoma, ameloblastic carcinomas are more aggressive with perforation of the cortical plate, extension into surrounding soft tissue,[18] lower lip paresthesia,[17] and persistent pain.[18] Furthermore, numerous recurrent lesions and metastasis, usually to cervical lymph nodes, bone, liver, and brain have been reported.[5],[19] In the series of ameloblastic carcinoma reported by Kruse et al.,[11] 34.6% revealed metastasis while 23.1% demonstrated local recurrence. Out of the 34.6% of metastasis, 26.9% was metastasis to the lungs, while only one case involved neck lymph nodes.[11] Dorner et al.[20] have also reported metastasis of ameloblastic carcinoma to the lungs. This high percentage of pulmonary metastasis emphasizes the importance of its detection using either computed tomography or positron emission tomography scans, as well as the need for long-term follow-up.[21]

 Radiographic Features



Ameloblastic carcinoma and ameloblastoma can have a comparable radiographical features; however, definite imaging features may aid the diagnostic feature.[22] Both lesions can be unilocular or multilocular radiolucencies with distinct borders in ameloblastomas but ill-defined borders in ameloblastic carcinomas. The borders may show slight marginal sclerosis without periosteal new bone formation.[22] There is loss of lamina dura and resorption of tooth apex.[22] In ameloblastic carcinoma, there is often the presence of focal radiopacity, apparently reflecting dystrophic calcification.[2],[23],[24]

 Diagnostic Criteria



The diagnostic criteria of an ameloblastic carcinoma that distinguishes it from ameloblastoma are based largely on cytologic atypia and increased mitotic figures.[25] When ameloblastic carcinoma arise de novo, the microscopic distinction from ameloblastoma is not very obvious and may be subjective.[17] The presence of numerous mitotic figures are unusual in ameloblastoma, cases where they are adequately numerous most likely will justify the diagnosis of ameloblastic carcinoma.[17] Existing literature suggests that the diagnosis of ameloblastic carcinoma is based on several arbitrary features, however four have been identified namely: (1) higher proliferative mitotic index emphasized by higher mitotic activity,[26] higher proliferating cell nuclear antigen expression and higher Ki67;[27] (2) nuclear atypia such as nuclear pleomorphism and basilar hyperplasia;[17] (3) hyperchromatic nuclei of basaloid cells;[17] and (4) other features of malignancy such as perineural or perivascular invasion.[17]

The main differential diagnosis of ameloblastic carcinoma is the basaloid variant of squamous cell carcinoma.[28] The distinguishing features of ameloblastic carcinoma from squamous cell carcinoma include, the jigsaw puzzle-type nesting of the tumor cells, the presence of stellate reticulum, and the distinctive cystic degeneration of the nests.[28] Another possible differential diagnosis is craniopharyngioma because of its similarities to odontogenic neoplasia and partially because of its location in the cranial base.[6]

 Treatment



Surgery is the mainstay of treatment,[12],[29] including prophylactic and therapeutic excision of involved lymph nodes.[30]En bloc removal with 1–2 cm of normal bone margin has been regarded as the safest surgical modality to ensure disease-free survival.[22] This method has resulted in local recurrence rates of <15%.[20] Some other authors have advocated 2- or 3-cm bony margins by the means of an en bloc removal.[8],[19] Ameloblastic carcinomas have been reported to recur locally 0.5–11 years after definitive therapy.[31] Some authors advocated the use of adjuvant radiotherapy,[29] however others have questioned its effectiveness.[11],[32] Philip et al.[33] have suggested adjuvant radiotherapy in patients with positive resection margins, multiple positive lymph nodes, extracapsular spread, perineural invasion, and those contraindicated for salvage surgery. Similarly, Roy Chowdhury et al.[17] have reported that radiotherapy and chemotherapy seem to be of narrow value; however, these methods need to be considered when there is a locally advanced or metastatic disease not amenable to surgical resection. Chemotherapy as primary treatment for nonmetastatic disease has been poor.[34] However, when there is metastatic disease, Ramadas et al.[35] found the use of cisplatin, adriamycin, and cyclophosphamide to be valuable. Methotrexate and leucovorin have been also used.[19]

 Prognosis



The major prognostic factor is the clinical course of the disease which include its aggressiveness, local destruction, and distant metastatic spread preferentially through hematologic route if neglected.[17] In addition, this relatively high risk of distant metastasis differs with that of squamous cell carcinomas that spread rather by the lymphatic way.[17] Distant metastasis is usually fatal and may appear as early as 4 months or as late as 12 years postoperatively.[31] However, once metastases occurred, the median survival have been reported to be 2 years.[28] It is also important to note that distant metastasis can occur in the absence of a local or regional recurrence.[13] The location of ameloblastic carcinoma also contributes to its prognosis as maxillary ameloblastic carcinoma have an unfavorable prognosis as compared to that located in the mandible.[12] In the Nigerian experience, recurrence ranged from 6 to 96 months after the initial surgery. Six patients died overall with three deaths within 3 years after the first surgery.[10] One patient died about 8 years after the initial surgery.[10]

Summary of differences between ameloblastic carcinoma and malignant ameloblastoma is given in [Figure 1].{Figure 1}

 Conclusion



Ameloblastic carcinoma is an uncommon unit of odontogenic tumors that exhibits malignant histologic features in the primary or distant metastasis. This is in contrast to malignant ameloblastoma where both primary and distant metastasis exhibit benign histologic features. It is imperative to consider it as a differential diagnosis in patients presenting with toothache or mobile teeth in association with persistent jaw swelling, pain, and rapid growth. Prognosis is good if early diagnosis is made with prompt surgical intervention, however, in neglected cases where there is distant metastasis, prognosis is guarded.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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