Malignant ameloblastoma or ameloblastic carcinoma

The World Health Organization defines malignant ameloblastoma as a lesion exhibiting features of an ameloblastoma in primary and metastatic growths. To cases collected from the literature we have added two of our own cases in which features of an ameloblastoma were coupled with malignant behavior. It was noted that the diagnosis of “malignant ameloblastoma” is at present used in a rather indiscriminate way, resulting in the grouping of lesions that exhibit considerable differences in biological behavior and histomorphology. This might be due to the fact that the WHO classification emphasizes metastasis as a diagnostic criterion but is rather vague in defining histopathologic aspects. It is advocated that the term malignant ameloblastoma be reserved for those lesions that, in spite of a seemingly innocuous histology, have given origin to metastatic growths, while the WHO classification should be modified to include ameloblastic carcinoma as a diagnostic term for lesions that combine features of an ameloblastoma with a less-differentiated histomorphology.     

Ameloblastic carcinoma ex ameloblastoma of the mandible with malignancy-associated hypercalcemia

Ameloblastoma is a rare, locally destructive, benign neoplasm of the jawbones, which arises from epithelium derived from the epithelial components of the developing tooth. Ameloblastic carcinoma is the term used to designate any ameloblastoma in which there is histologic evidence of malignancy in the primary tumor, regardless of whether it has metastasized. Most ameloblastic carcinomas are presumed to have arisen de novo, with few cases of malignant transformation of ameloblastoma being apparent. Hypercalcemia is the most common metabolic complication of malignancy. Although malignancy-associated hypercalcemia is often reported in association with other malignancies, it is exceedingly unusual in association with ameloblastoma, malignant ameloblastoma, or ameloblastic carcinoma. We describe a patient with multiple recurrences of ameloblastoma, with subsequent malignant transformation presenting with malignancy-associated hypercalcemia.     

Ameloblastic Carcinoma of the mandible

Odontogenic carcinomas are rare lesions arising from dental embryogenic residues and have been designated by a variety of terms like malignant ameloblastoma, ameloblastic carcinoma, metastatic ameloblastoma or primary intra-alveolar epidermoid carcinoma. Ameloblastic carcinoma combines the histological features of ameloblastoma with cytological atypia, even in the absence of metastasis. The lesion has been reported to arise either from the odontogenic cyst or the ameloblastoma. Majority originate de novo and the remaining are malignant transformation of an ameloblastoma.     

Ameloblastic Carcinoma

Ameloblastic carcinoma (AC) is a rare aggressive malignant epithelial odontogenic tumor of the maxillofacial skeleton with a distinct predilection in the mandible. It may appear de novo or originate from a pre-existing ameloblastoma or odontogenic cyst. It exhibits cytological features of ameloblastoma and carcinoma. It may present as a cystic lesion with benign clinical features or as a large tissue mass with ulceration, significant bone resorption and tooth mobility. The clinical course of ameloblastic carcinoma is typically aggressive, with extensive local destruction. Direct extension of the tumour, lymph node involvement and metastasis to various sites has been reported. Wide local excision is the treatment of choice. Regional lymph node dissection should be considered and performed selectively. Radiotherapy and chemotherapy have limited role in the treatment of ameloblastic carcinomas. Close periodic reassessment of the patient is mandatory.     

Ameloblastic carcinoma: case report and literature review

Ameloblastic carcinoma is a rare malignant lesion with characteristic histologic features and behaviour that dictates a more aggressive surgical approach than that of a simple ameloblastoma. However, reliable evidence of its biologic activity is currently unavailable due to the scarcity of well-documented cases. It occurs primarily in the mandible in a wide range of age groups; no sex or race predilection has been noted. It may present as a cystic lesion with benign clinical features or as a large tissue mass with ulceration, significant bone resorption and tooth mobility. Because the lesion is usually found unexpectedly after an incisional biopsy or the removal of a cyst, a guide to differential diagnosis is not usually useful. The identifying features of ameloblastic carcinoma must be known and recognized by dental practitioners. Our understanding of the histologic features of ameloblastic carcinoma is somewhat vague. The tumour cells resemble the cells seen in ameloblastoma, but they show cytologic atypia. Moreover, they lack the characteristic arrangement seen in ameloblastoma. The clinical course of ameloblastic carcinoma is typically aggressive, with extensive local destruction. Direct extension of the tumour, lymph node involvement and metastasis to various sites (frequently the lung) have been reported. Wide local excision is the treatment of choice. Regional lymph node dissection should be considered and performed selectively. Radiotherapy and chemotherapy seem to be of limited value for the treatment of ameloblastic carcinomas. At the moment, there are too few reported cases to make a definite recommendation regarding treatment. Close periodic reassessment of the patient is mandatory.     

Ameloblastic carcinoma ex ameloblastoma: report of a case-possible involvement of CpG island hypermethylation of the p16 gene in malignant transformation

Ameloblastic carcinoma is described in the updated World Health Organization (WHO) classification as a rare malignant lesion. Ameloblastic carcinoma meeting the WHO criteria may arise either as a result of malignant change in a pre-existing benign ameloblastoma (carcinoma ex ameloblastoma) or as a primary malignant ameloblastoma not preceded by an ordinary ameloblastoma (de novo carcinoma). We report a case of ameloblastic carcinoma ex ameloblastoma and examine how this case underwent malignant transformation. The DNA was extracted separately from benign and malignant areas in paraffin sections of the tumor. Direct sequencing showed no genetic mutation of exons 5-8 of the p53 gene. Hypermethylation of CpG islands of the p16 gene was detected in the malignant parts of the tumor. The results indicate that hypermethylation of p16 may have been involved in the malignant transformation of the ameloblastoma in the present case.     

Ameloblastic carcinoma, secondary type: a case report

Malignant variants of ameloblastoma include metastasizing ameloblastoma, which microscopically appears benign but has metastasized and ameloblastic carcinoma that exhibits malignant histopathologic features. Ameloblastic carcinoma is classified into 2 types: a primary odontogenic malignancy and a secondary type resulting from malignant transformation of ameloblastoma. Most secondary ameloblastic carcinomas result from malignant transformation of a primary lesion after repeated postsurgical recurrences. Therefore it is rare to find an untreated secondary type presenting with histologic features of malignant transformation from an earlier benign lesion. We experienced a rare case of ameloblastic carcinoma, secondary type which might arise in an untreated ameloblastoma. The mechanism by which a preexisting benign ameloblastoma goes through a malignant transformation is also described.     

恶性造釉细胞瘤和造釉细胞癌的病理学研究

为探讨恶性造釉细胞瘤和造釉细胞癌的临床病理特点，及两个名称的自然历史和意义，我们对２４例恶性造釉细胞瘤（造釉细胞癌）的临床病理资料进行了研究，并对两个名称各自的实质进行了探讨。结果：其组织病理特点为滤泡周边细胞增生，可呈乳头状突向间质，核增大中度异型，核深染或呈空泡状，核分裂相增加，星网状细胞消失被肉瘤样细胞取代。其中１９例５～３０年随访结果为：１１例生存；３例１次复发，３例２次复发（其中１例复发后死亡），１例４次复发后死亡，１例１３年无复发死于它病。结果提示：“恶性造釉细胞瘤”这一名称更为科学。     

Ameloblastic carcinoma: a case report with radiological features of computed tomography and magnetic resonance imaging and positron emission tomography

Ameloblastic carcinoma is a rare malignant odontogenic carcinoma that has metastatic potential, and because of its rare incidence, there are few reports focusing on its radiologic imaging. If it shows aggressive appearances, it can be diagnosed as malignant tumor. But in case of negative appearance, it is difficult to distinguish ameloblastic carcinoma from ameloblastoma. We report a case of ameloblastic carcinoma of the maxilla in a 76-year-old female patient with radiologic images and pathologic features.     

Ameloblastic carcinoma of the jaws: A report of two cases

Two cases of ameloblastic carcinoma of the jaws are reported. Histopathologically, the lesions showed cytologic features of malignancy in addition to classical ameloblastoma patterns and were therefore documented as examples of ameloblastic carcinoma. The negative cytokeratin expression by the malignant cells on histochemical analysis is notably different from that normally observed in classical ameloblastomas.     

Ameloblastic carcinoma of the mandible resembling odontogenic cyst in a panoramic radiograph

Ameloblastic carcinoma is a rare odontogenic tumor exhibiting histologic evidence of malignancy in the primary or recurrent tumor, regardless of whether it has metastasized or not. Most ameloblastic carcinomas are presumed to have arisen de novo, with few cases of malignant transformation of ameloblastoma being apparent. A case is reported of a 21-year-old caucasian female with ameloblastic carcinoma in the left angulus area of the mandible resembling an odontogenic cyst in the panoramic radiograph. In addition to the panoramic radiograph, computerized tomography (CT) and magnetic resonance (MR) images were taken preoperatively. This report demonstrates that CT or MR examinations may be crucial in differentiating odontogenic tumors from cysts.     

Ameloblastic carcinoma: case report and review

The histologic classification for odontogenic carcinomas is still under revision; thus, the differentiation between the terms "malignant ameloblastoma" and "ameloblastic carcinoma" has not been definitely stated. Nevertheless, it is recommended to reserve the former for those lesions that, in spite of an apparently innocuous histology, have given origin to metastatic growths, and to apply the latter for those ameloblastomas in which there is histologic evidence of malignancy in the primary, recurrent or metastatic lesions. A case of an ameloblastic carcinoma in the mandible is presented. Histologically, it was characterized by areas with features of a typical ameloblastoma and areas with anaplastic appearances.     

A case of ameloblastic carcinoma with pulmonary metastases

A case initially thought to be ameloblastoma of the mandible which showed rapid local destruction and was demonstrated to have three pulmonary metastases post mortem 18 months after the first symptoms in the mandible. The diagnosis is now considered to be ameloblastic carcinoma. The difficulties in histological diagnosis and varying classifications of malignant odontogenic tumours is noted.     

Ameloblastoma and its relationship to ameloblastic fibroma: their histogenesis based on an unusual case and review of the literature.

The present paper describes the relationship between ameloblastoma and ameloblastic fibroma deduced from a case diagnosed as "ameloblastoma combined with ameloblastic fibroma" arising in the mandible of a 5-year-old boy. Histologically, the tumor consisted of ameloblastoma in the central area and ameloblastic fibroma in the peripheral area; it clinically fits the characteristics of ameloblastic fibroma based on predominant age, manner of growth, and encapsulation. We reviewed the literature and discussed the relationship between ameloblastoma a ameloblastic fibroma in terms of tumorigenesis. It is assumed that ameloblastic fibroma can also be transformed into ameloblastoma, if the succeeding hard tissues are not formed, and the collagenous connective tissue substituting for the stromal mesenchymal tissue is formed by the inductive effect of the epithelial strands or other unknown factors. Several possibilities relative to the pathogenesis of ameloblastoma have been proposed by oral pathologists; however, to our knowledge, "ameloblastic fibroma can be transformed into ameloblastoma" has not hitherto been reported. The case we experienced here may be thought as an intermediate tumor pattern between ameloblastic fibroma and ameloblastoma.     

Ameloblastic carcinoma of the jaws. A report of three Nigerian cases.

Ameloblastic carcinoma is an exceptionally rare and aggressive orofacial neoplasm that belongs to a family of malignant epithelial odontogenic tumours. The aetiology remains largely unknown, however most cases are presumed to have arisen de novo, with few of them presenting following malignant transformation of ameloblastoma. We report our experience with three rare cases of ameloblastic carcinoma seen in Nigerians. This is an addition to the sparse literature and to our knowledge; there has been no such report from sub-Saharan Africa.     

CEA immunoreactivity in odontogenic tumors and keratocysts

Forty-five oral tumors and cysts were stained immunohistochemically for the presence of carcinoembryonic antigen (CEA). CEA, or a CEA-like antigen that is not nonspecific cross-reacting antigen (NCA), was demonstrated in the majority of aggressive or malignant tumors showing squamous differentiation, including cases of ameloblastoma, odontogenic carcinoma, and squamous carcinoma. CEA immunoreactivity was also found in cases of odontogenic keratocyst and focally in squamous odontogenic tumors but was not found in any of the ameloblastic fibromas, myxofibromas, odontogenic adenomatoid tumors, malignant melanomas, or apical cysts.     

Odontogenic tumors: analysis of 706 cases.

From a total of 54,534 oral biopsy specimens, 706 (1.3%) odontogenic tumors were retrieved and reviewed. Odontomas comprised more than 65% of the odontogenic tumors, ameloblastomas about 10%, and the remaining six categories of odontogenic tumors accounted for approximately 25% of the lesions. The distribution by age, sex, and location of these tumors generally supported the data from other previously reported cases. A possible variant of the calcifying epithelial odontogenic tumor was described, and instances of two granular cell ameloblastic fibromas were reported. The myxomas as a group were characterized histologically more by residual bony trabeculae than by the presence of odontogenic rests. Because the clinical, histological, and behavioral features of the ameloblastic fibroma and ameloblastic fibro-odontoma were similar, these lesions were considered to be essentially the same. From limited follow-up information, the ameloblastoma was the only lesion that recurred. With the exception of one ameloblastoma found in the lung, no malignant odontogenic tumors were encountered.     

RECK基因和基质金属蛋白酶-2在成釉细胞瘤的表达及相关性研究

目的探讨RECK和基质金属蛋白酶-2（MMP-2）的表达与成釉细胞瘤（AB）临床生物学行为的关系及相关性。方法应用免疫组化EliVision^TM plus法检测69例AB（原发45例,复发24例）、6例成釉细胞癌和16例牙源性角化囊性瘤（KCOT）中RECK、MMP-2蛋白的表达,同时采用RT-PCR方法检测22例AB（原发12例,复发10例）、2例成釉细胞癌和16例KCOT中RECK、MMP-2mRNA的表达水平。所有数据采用SPSS13．0统计软件包进行统计学分析。结果RECK蛋白的阳性表达率在KCOT、AB和成釉细胞癌中依次明显降低（P〈0．05）,且复发AB显著低于原发AB（P〈0．01）;AB和成釉细胞癌的MMP-2蛋白阳性表达率均显著高于KCOT（P〈0．05）：RECK蛋白与MMP-2蛋白在AB中的表达呈负相关（r=-0．431,P〈0．001）。RECKmRNA在AB、KCOT中均见表达,但在AB的表达较KCOT显著降低（P〈0．001）．成釉细胞癌中则无表达：MMP-2mRNA在KCOT、AB和成釉细胞癌中均见表达,但在AB的表达水平较KCOT显著增高（P〈0．001）,在成釉细胞癌中均呈高水平表达：复发AB的RECKmRNA表达水平较原发AB显著降低（P〈0．05）,但复发与原发AB的MMP-2mRNA表达之间差异无统计学意义：RECKmRNA与MMP-2mRNA在AB中的表达水平无相关性（P〉0．05）。结论RECK表达降低或缺失及MMP-2表达增高与AB的临床生物学行为密切相关。RECK可能通过转录后水平调控MMP-2参与AB的侵润、复发和恶性转化过程。     

Ameloblastoma: analysis of 207 cases in a Nigerian teaching hospital.

OBJECTIVE: The aim of the study was to review all the cases of ameloblastoma seen at the Oral and Maxillofacial Surgery Clinic of the Lagos University Teaching Hospital, Nigeria, between 1980 and 2003. METHODS AND MATERIALS: In this retrospective study, case files and biopsy reports of new cases of ameloblastoma covering a 24-year period were retrieved and analyzed for sex, age on presentation, histologic type, and site distribution. RESULTS: A total of 207 cases of ameloblastoma were seen in the given period. One hundred and ninety-eight (95.7%) were benign, and 9 (4.3%) were malignant. A male-to-female ratio of 1.1:1 was found. The average ages on presentation for ameloblastoma and ameloblastic carcinoma were 31.67 and 46.44 years, respectively. The lesion was found to be more common in the premolar-molar region of the mandible. The most common histologic type was follicular ameloblastoma (25.1%). Nine (4.3%) cases of ameloblastic carcinoma were also reported. CONCLUSIONS: Ameloblastoma with a predilection for the posterior mandibular region is relatively common in our environment. Sex and site distributions are similar to previous reports in the literature.