Immunohistochemical demonstration of enamel proteins in odontogenic tumors

Adenomatoid odontogenic tumor: A histopathologic profile of 43 cases with evidence supporting a mixed odontogenic origin

BACKGROUND

Adenomatoid Odontogenic Tumor (AOT) accounts for 3% of all odontogenic tumors. It has been classified by WHO as an odontogenic tumor of purely epithelial origin. The current study attempts to establish the origin of the tumor along with detailed histopathological and clinicoradiographic analysis of 43 cases of AOT.

MATERIAL AND METHODS

Forty-three cases were reviewed from the departmental archives for demographic data, radiographic features and histological features. Further, histopathological slides were stained with Picrosirius Red (PSR) and observed under polarised light.

RESULTS

A majority of the cases were seen in the anterior jaws (76.7%), and were less than 3 cms (76.7%) in greatest dimension. Equal number of cases were of follicular and extra-follicular location while one was peripheral. Predominantly solid histological pattern was noted in 53.5%. Varied sub-patterns were observed with most cases exhibiting solid nodules and strands of tumor cells. Few cases showed melanin pigmentation. Over a third of cases (37.2%) showed dentigerous cyst like areas and one case each showed features of ossifying fibroma and focal cemento-osseous dysplasia. Tumor droplets, hyaline rings within duct-like structures, dentinoid material and osteodentin showed reddish yellow birefringence when observed under polarised microscopy post PSR staining.

CONCLUSION

This study highlights the diverse histopathological variation of AOT with evidence to reclassify it as a mixed odontogenic tumor based on the polarising microscopic findings with PSR staining.

Adenomatoid Odontogenic Tumor of the Maxilla in a 13-year-old Patient: A Rare Case Report with a Review of Literature

Background

The AOT is an atypical tumor of odontogenic origin that comprises about 0.1% of jaw tumors and cysts as well as up to 3% of odontogenic tumors (OTs).

Aim and objective

This review describes the clinical, radiographical, histopathological, and immunohistochemical properties of adenomatoid odontogenic tumor (AOT) and reports an occurrence of an AOT in a boy, 13 years of age.

Case description

A male, 13 years of age, presented with a swelling with respect to the left maxilla, painless, and with obvious facial asymmetry. The orthopantomogram and computed tomography scan revealed a large unilocular radiolucency in the left maxilla with permanent lateral incisor embedded within the lesion and permanent canine pushed away from its normal position. After complete enucleation of the cyst under local anesthesia and extraction of associated impacted permanent teeth and retained deciduous teeth related to the lesion, the defect was filled with a bone graft and closed. Postoperative follow-up was uneventful.

Conclusion

An accurate diagnosis should be established through clinical, radiographical, and pathological correlations in order to be able to differentiate AOT from other conditions for early diagnosis.

Clinical significance

This report highlights the salient features of the AOT to be able to correctly diagnose and manage the lesion.

How to cite this article

Kamble A, Shimpi MR, Dash JK, et al. Adenomatoid Odontogenic Tumor of the Maxilla in a 13-year-old Patient: A Rare Case Report with a Review of Literature. Int J Clin Pediatr Dent 2021;14(4):596–600.

Amelogenin in calcified matrices of odontogenic cysts and odontogenic tumors: An immunohistochemical study

Background/purpose

There are few studies comparing the expression of enamel proteins, such as amelogenin, and cytokeratins in cyst and odontogenic tumors like in ameloblastoma and odontogenic keratocyst, indicating that amelogenin could be a potential biomarker for the aggressiveness in the odontogenic tumors. The aim of this study was to evaluate if the expression of amelogenin, cytokeratin AE1/AE3 (CKAE1/AE3) and cytokeratin 14 (CK14) in cysts and odontogenic tumors with calcified matrices such as calcifying odontogenic cyst (COC), compound (CdO) and complex (CxO) odontomas, adenomatoid odontogenic tumor (AOT) and calcifying epithelial odontogenic tumor (CEOT) as an aggressiveness indicator.

Materials and methods

Three COC, eight CxO, three CdO, twelve AOT, two CEOT and three dental germs were submitted to an immunohistochemistry panel of antibodies composed of amelogenin, CKAE1/AE3 and CK14.

Results

CKAE1/AE3 and CK14 was present in all odontogenic epithelia. The amelogenin protein was detected in prismatic and amorphous calcified matrices of epithelial origin belonging to CxO, CdO, AOT, COC and the tooth germs used as controls. On the other hand, the CEOT was the only tumor or cyst studied that did not present immunostaining for amelogenin in calcified matrices.

Conclusion

Amelogenin was detected in pathologies with a low or absent recurrence rate and excellent prognosis. CEOT was the lesion of greater clinical aggressiveness which did not express amelogenin. The presence of amelogenin in calcified matrices of odontogenic arise could be an indicator of low aggressiveness.

Immunohistochemical detection of Tyrosine Kinase receptor (TrK) in follicular and plexiform ameloblastoma - A novel study

Objectives:

The objective is to analyze the immunohistochemical expression pattern of tyrosine kinase receptor (TrK) in ameloblastoma and to compare the immunohistochemical expression pattern of TrK among the histological types of ameloblastoma, follicular and plexiform patterns.

Materials and Methods:

Forty ameloblastomas (20 follicular and 20 plexiform) were immunostained with anti-human TrK mouse IgG monoclonal antibody, and the pattern of staining is statistically analyzed.

Results:

Total 20 (4 follicular and 16 plexiform) out of 40 ameloblastomas showed immunoreactivity to TrK. Only the peripheral preameloblast like tall columnar cells showed reactivity, whereas the stellate reticulum like cells is immunonegative. The staining pattern was membranous in the immunoreactive cells. The Chi-square value for the immunoexpression between follicular and plexiform ameloblastoma was statistically significant with a P < 0.005. The results were studied with the downstream pathways from the literature, and a possible mechanism has been proposed.

Conclusion:

The expression pattern of TrK is found to be more in plexiform ameloblastoma than follicular ameloblastoma.

Amelogenin is a Potential Biomarker for the Aggressiveness in Odontogenic Tumors

Amelogenin (AMEL), the major structural protein of the enamel organic matrix, constitutes more than 90% of the enamel’s protein content, Aberrations of amelogenin are thought to be involved in the oncogenesis of odontogenic epithelium. The expression of amelogenin is possibly an indicator of differentiation of epithelial cells in the odontogenic tumors. Aim of the study: Investigating the expression of amelogenin in some odontogenic tumors, using an anti-amelogenin polyclonal antibody, and then compare it with AMEL expression in tooth buds as control. Materials and Methods: study sample consisted of 10 formalin-fixed, paraffin- embedded specimens of ameloblastoma, 10 Keratocystic odontogenic tumors, and 10 tooth buds were conventionally stained with hematoxylin-eosin and immunohistochemically with AMEL polyclonal antibody. Results: All of the odontogenic tumors expressed AMEL in the epithelial component, Intensity of expression in ameloblastoma and Keratocystic odontogenic tumor was lower, compared with tooth buds, Statistical analysis indicated a significant differences between the tumors and tooth buds. Conclusion: Amelogenin can be used as a marker for odontogenic epithelium, and the expression of amelogenin is possibly an indicator of epithelial cells differentiation in the odontogenic tumors, and therefore in prediction of the histological behavior of odontogenic tumors.

Cancer genes mutation profiling in calcifying epithelial odontogenic tumour

Aims

To identify calcifying epithelial odontogenic tumour (CEOT) mutations in oncogenes and tumour suppressor genes.

Methods

A panel of 50 genes commonly mutated in cancer was sequenced in CEOT by next-generation sequencing. Sanger sequencing was used to cover the region of the frameshift deletion identified in one sample.

Results

Missense single nucleotide variants (SNVs) with minor allele frequency (MAF) <1% were detected in PTEN, MET and JAK3. A frameshift deletion in CDKN2A occurred in association with a missense mutation in the same gene region, suggesting a second hit in the inactivation of this gene. APC, KDR, KIT, PIK3CA and TP53 missense SNVs were identified; however, these are common SNVs, showing MAF >1%.

Conclusion

CEOT harbours mutations in the tumour suppressor PTEN and CDKN2A and in the oncogenes JAK3 and MET. As these mutations occurred in only one case each, they are probably not driver mutations for these tumours.

Immunohistochemical Detection of p75 Neurotrophin Receptor (p75-NTR) in Follicular and Plexiform Ameloblastoma

INTRODUCTION

Ameloblastoma holds a unique position among benign tumours by its locally destructive and invasive nature. Recently improvised molecular techniques helped researchers to unravel the myth behind such biologic behaviour. Though interesting findings have been delivered, the rhythmic correlation regarding the exact mechanism still remains lacking. Neurotrophins and their receptor mediated pathways play a crucial role in survival, death and differentiation of many neuroectoderm derived cells. With this background, the study has been aimed to investigate the expression of p75-NTR (Neurotrophin Receptor) in follicular and plexiform ameloblastoma.

AIM

To analyze the immunohistochemical expression pattern of p75-NTR in ameloblastoma and to compare the immunohistochemical expression pattern of p75-NTR among the histological types of ameloblastoma, follicular and plexiform patterns.

MATERIALS AND METHODS

Total 22 ameloblastomas (12 follicular, 10 plexiform) were immuno-stained with anti-human p75-NTR mouse IgG monoclonal antibody and the pattern of staining is statistically analyzed.

RESULTS

Only 11 (10 follicular, 1 plexiform) out of 22 ameloblastomas showed immuno-reactivity to p75-NTR. In ameloblastoma, only the peripheral pre-ameloblast like tall columnar cells showed reactivity whereas the stellate reticulum-like cells were immuno-negative. The staining pattern was membranous in the immuno-reactive cells. The results were studied with the downstream pathways from the literature and a possible mechanism has been proposed.

CONCLUSION

The expression pattern of p75-NTR was found to be more in follicular ameloblastoma than plexiform.

A case report and short review on changing trends in the site of occurrence of adenomatoid odontogenic tumor: Unravelling the past 15 years

Adenomatoid odontogenic tumor (AOT) is an uncommon benign odontogenic lesion, with debatable histogenesis and variable histopathology. A systematic and diverse insight into the evolution, clinical presentation, histology, and immunohistochemical findings of this lesion is reviewed and presented. We reviewed the data published from 2000 to 2014 of approximately 255 cases that revealed a significant change in the incidence of predominant site involved, in contrast to the findings published by Reichart. We have also included the chronological order of events leading to the coining of the term AOT, which shows the curiosity that has been dedicated to understanding the lesion. Immunohistochemistry is considered to be a hallmark in pathology for learning the molecular pathogenesis and giving a correct final diagnosis. Several markers have been used to investigate and understand this lesion, and a compilation of the findings has been tabulated.

Cytokeratin 14 and cytokeratin 18 expressions in reduced enamel epithelium and dentigerous cyst: Possible role in oncofetal transformation and histogenesis- of follicular type of adenomatoid odontogenic tumor

Introduction:

Odontogenic cysts and tumors arise from the structures and remnants associated with tooth development. Cysts and tumors derived from the odontogenic tissues constitute an unusually diverse group of lesions. This diversity reflects the complex development of the dental structures, since all these lesions originate through some alteration from the normal pattern of odontogenesis. Cytokeratin (CK) 14 is the typical intermediary filament of odontogenic epithelium, CK 18 is the major components of the intermediate filaments of simple or single layered epithelial tissue; it is not expressed in stratified squamous epithelium. The present study was undertaken to understand the expression pattern of these cytokeratins in dentigerous cyst, dental follicular tissue, adenomatoid odontogenic tumor (AOT) and unicystic ameloblastoma.

Materials and Methods:

The present study consists of 60 specimens consisting of 20 samples of Dentigerous cyst, 20 samples of Reduced enamel epithelium/dental follicles, 10 samples of Follicular type of AOT, 10 samples of unicystic ameloblastoma. The sections of these specimens were stained for CK 14 and CK 18. The number of cells positive for CK 14 and CK 18 was counted per 100 cells. The cells were counted in four randomly selected high-power fields and the mean was calculated. Scoring of cytokeratin 14 expressions was done using Remmele score.

Results:

The highest expression of cytokeratin 14 was noted in AOT, least was seen in dental follicle/Reduced enamel epithelium (REE). CK18 was negative in all the cases included in the present study.

Conclusion:

In the present study, the expression of CK14 was noted in AOT, Dentigerous cyst (DC), Unicystic Ameloblastoma (UCA) and Dental follicle/REE. The expressions between these lesions were compared. These expression pattern may provide an insight to the histogenesis of AOT.

Amelogenin in odontogenic cysts and tumors: An immunohistochemical study

Background:

Amelogenins are the major enamel proteins that play a major role in the biomineralization and structural organization of enamel. Aberrations of enamel-related proteins are thought to be involved in oncogenesis of odontogenic epithelium. The expression of amelogenin is possibly an indicator of differentiation of epithelial cells in the odontogenic lesions.

Aims and Objectives:

The present study aimed to observe the expression of amelogenin immunohistochemically in various odontogenic lesions.

Materials and Methods:

Paraffin sections of 40 odontogenic lesions were stained immunohistochemically with amelogenin antibodies. The positivity, pattern and intensity of expression of the amelogenin antibody were assessed, graded and statistically compared between groups of odontogenic cysts and tumors.

Results:

Almost all the odontogenic lesions expressed amelogenin in the epithelial component with the exception of an ameloblastic carcinoma. Differing grades of intensity and pattern were seen between the cysts and tumors. Intensity of expression was uniformly prominent in all odontogenic lesions with hard tissue formation. Statistical analysis however did not indicate significant differences between the two groups.

Conclusion:

The expression of amelogenin antibody is ubiquitous in odontogenic tissues and can be used as a definitive marker for identification of odontogenic epithelium.

Adenomatoid odontogenic tumour in mandible in a 14-year-old boy

A 14-year-old boy reported with a painless swelling over the right anterior mandible with missing right canine tooth. The lesion was diagnosed as 'central follicular adenomatoid odontogenic tumour' and excised surgically under general anaesthesia. The patient was on a year-long clinical and radiographical follow-up.

Current concepts and occurrence of epithelial odontogenic tumors: I. Ameloblastoma and adenomatoid odontogenic tumor

Ameloblastomas and adenomatoid odontogenic tumors (AOTs) are common epithelial tumors of odontogenic origin. Ameloblastomas are clinico-pathologically classified into solid/multicystic, unicystic, desmoplastic, and peripheral types, and also divided into follicular, plexiform, acanthomatous, granular types, etc., based on their histological features. Craniopharyngiomas, derived from the remnants of Rathke's pouch or a misplaced enamel organ, are also comparable to the odontogenic tumors. The malignant transformation of ameloblastomas results in the formation of ameloblastic carcinomas and malignant ameloblastomas depending on cytological dysplasia and metastasis, respectively. AOTs are classified into follicular, extrafollicular, and peripheral types. Ameloblastomas are common, have an aggressive behavior and recurrent course, and are rarely metastatic, while AOTs are hamartomatous benign lesions derived from the complex system of the dental lamina or its remnants. With advances in the elucidation of molecular signaling mechanisms in cells, the cytodifferentiation of epithelial tumor cells in ameloblastomas and AOTs can be identified using different biomarkers. Therefore, it is suggested that comprehensive pathological observation including molecular genetic information can provide a more reliable differential diagnosis for the propagation and prognosis of ameloblastomas and AOTs. This study aimed to review the current concepts of ameloblastomas and AOTs and to discuss their clinico-pathological features relevant to tumorigenesis and prognosis.

Adenomatoid odontogenic tumor: retrospective study of 15 cases with emphasis on histopathologic features

Adenomatoid odontogenic tumor (AOT) is an uncommon benign epithelial lesion of odontogenic origin and, thus far, only few studies regarding the frequency of its many histopathologic features have been published in the literature. Thus, the aim of this study was to perform a retrospective analysis in a case series of AOT, with emphasis on the histopathological features. Fifteen cases of AOT were studied considering their clinical, radiographic and histopathologic aspects. Twelve cases affected females and the mean age was 16.2 years. The anterior maxilla was the most common site (66.6 %) and radiographically most cases showed a unilocular radiolucency with well-defined borders (57.1 %). Histologically, most cases exhibited predominantly a solid growth pattern (46.7 %) or a similar proportion of solid and cribriform patterns (46.7 %). Eosinophilic amorphous material ("tumor droplets") was found in all cases (100 %). Most tumors showed duct-like spaces (93.3 %) and convoluted structures (60.0 %) whereas a minor proportion of cases presented calcifying epithelial odontogenic tumor (CEOT)-like areas (26.7 %). Variable amounts of calcified material were found in most AOTs (80.0 %) whereas osteodentin and perivascular hyalinization were seen only rarely (6.7 % each one). Five (33.3 %) cases had areas mimicking a dentigerous cyst and most of these were diagnosed in females (80.0 %). Regarding the histopathologic features, our results suggest that AOTs usually show predominance of solid pattern or a similar proportion of solid and cribriform patterns while osteodentin and perivascular hyalinization are rarely seen in these tumors. In addition, areas mimicking a dentigerous cyst and CEOT-like areas are relatively infrequent findings in AOTs.

Expression of odontogenic ameloblast-associated protein, amelotin, ameloblastin, and amelogenin in odontogenic tumors: immunohistochemical analysis and pathogenetic considerations

Screening for expression of amelogenesis-related proteins represents a powerful molecular approach to characterize odontogenic tumors and investigate their pathogenesis. In this study, we have examined the presence and distribution of odontogenic ameloblast-associated protein (ODAM), amelotin (AMTN), ameloblastin (AMBN), and amelogenin (AMEL) by immunohistochemistry in samples of adenomatoid odontogenic tumor (AOT), calcifying epithelial odontogenic tumor (CEOT), developing odontoma, ameloblastoma, calcifying cystic odontogenic tumor (CCOT), ameloblastic fibroma (AF), myxoma, odontogenic fibroma (OF), and reduced enamel epithelia (REE). Positive results were obtained in those tumors with epithelial component, except for AF, OF, and ameloblastoma. ODAM was found around mineralized structures (dystrophic calcifications) and CEOT's amyloid, whereas AMTN stained the eosinophilic material of AOTs. The CCOT transitory cells to ghost cells were strongly positive with all proteins except AMEL, and the REE as well as odontomas showed immunoexpression for ODAM, AMTN, AMBN, and AMEL similar to those found in normal rat tooth germs. Based on these results, some histopathogenetic theories were formulated.

An amelogenin mutation leads to disruption of the odontogenic apparatus and aberrant expression of Notch1

BACKGROUND

Amelogenins are highly conserved proteins secreted by ameloblasts in the dental organ of developing teeth. These proteins regulate dental enamel thickness and structure in humans and mice. Mice that express an amelogenin transgene with a P70T mutation (TgP70T) develop abnormal epithelial proliferation in an amelogenin null (KO) background. Some of these cellular masses have the appearance of proliferating stratum intermedium, which is the layer adjacent to the ameloblasts in unerupted teeth. As Notch proteins are thought to constitute the developmental switch that separates ameloblasts from stratum intermedium, these signaling proteins were evaluated in normal and proliferating tissues.

METHODS

Mandibles were dissected for histology and immunohistochemistry using Notch1 antibodies. Molar teeth were dissected for western blotting and RT-PCR for evaluation of Notch levels through imaging and statistical analyses.

RESULTS

Notch1 was immunolocalized to ameloblasts of TgP70TKO mice, KO ameloblasts stained, but less strongly, and wild-type teeth had minimal staining. Cells within the proliferating epithelial cell masses were positive for Notch1 and had an appearance reminiscent of calcifying epithelial odontogenic tumor with amyloid-like deposits. Notch1 protein and mRNA were elevated in molar teeth from TgP70TKO mice.

CONCLUSION

Expression of TgP70T leads to abnormal structures in mandibles and maxillae of mice with the KO genetic background and these mice have elevated levels of Notch 1 in developing molars. As cells within the masses also express transgenic amelogenins, development of the abnormal proliferations suggests communication between amelogenin producing cells and the proliferating cells, dependent on the presence of the mutated amelogenin protein.

Calcifying epithelial odontogenic tumor (Pindborg tumor)

The calcifying epithelial odontogenic tumor is a benign epithelial tumor with characteristic clinical and histopathologic features. These features are discussed with a typical case presentation along with emphasis on newer variants and management strategies.

Review article: Current concepts of ameloblastoma pathogenesis

Ameloblastoma is a locally destructive and invasive tumour that can recur despite adequate surgical removal. Molecular studies have offered interesting findings regarding ameloblastoma pathogenesis. In the present review, the following topics are discussed regarding its molecular nature: clonality, cell cycle proliferation, apoptosis, tumour suppressor genes, ameloblastin and other enamel matrix proteins, osteoclastic mechanism and matrix metalloproteinases and other signalling molecules. It is clear from the literature reviewed that translational studies are necessary to identify prognostic markers of ameloblastoma behaviour and to establish new diagnostic tools to the differential diagnosis of unicystic from multicystic ameloblastoma. Finally, molecular biology studies are also important to develop more effective alternative approaches to the treatment of this aggressive odontogenic tumour.

Critical role of heparin binding domains of ameloblastin for dental epithelium cell adhesion and ameloblastoma proliferation

AMBN (ameloblastin) is an enamel matrix protein that regulates cell adhesion, proliferation, and differentiation of ameloblasts. In AMBN-deficient mice, ameloblasts are detached from the enamel matrix, continue to proliferate, and form a multiple cell layer; often, odontogenic tumors develop in the maxilla with age. However, the mechanism of AMBN functions in these biological processes remains unclear. By using recombinant AMBN proteins, we found that AMBN had heparin binding domains at the C-terminal half and that these domains were critical for AMBN binding to dental epithelial cells. Overexpression of full-length AMBN protein inhibited proliferation of human ameloblastoma AM-1 cells, but overexpression of heparin binding domain-deficient AMBN protein had no inhibitory effect. In full-length AMBN-overexpressing AM-1 cells, the expression of Msx2, which is involved in the dental epithelial progenitor phenotype, was decreased, whereas the expression of cell proliferation inhibitors p21 and p27 was increased. We also found that the expression of enamelin, a marker of differentiated ameloblasts, was induced, suggesting that AMBN promotes odontogenic tumor differentiation. Thus, our results suggest that AMBN promotes cell binding through the heparin binding sites and plays an important role in preventing odontogenic tumor development by suppressing cell proliferation and maintaining differentiation phenotype through Msx2, p21, and p27.

Expression of basement membrane components in odontogenic tumors

OBJECTIVE

The objective was to characterize the expression of BMCs (laminins 1 and 5, collagen type IV, and fibronectin) in ameloblastomas, calcifying cystic odontogenic tumors (CCOTs), and adenomatoid odontogenic tumors (AOTs).

STUDY DESIGN

BMCs were analyzed in 14 ameloblastomas, 7 CCOTs, and 7 AOTs using immunohistochemistry.

RESULTS

In normal oral mucosa, linear deposits of these proteins were found at the epithelial-mesenchymal junction, but not in epithelial cytoplasm. In all tumors studied, linear deposits of all proteins were found at the epithelial-mesenchymal junction; laminin 1 was expressed in all tumor cells, regardless of cell types. For CCOTs, laminin 5 was found faintly in suprabasal cells, but expressed strongly in ghost cells. For AOTs, laminin 5 strongly decorated tumor cells adjacent to mineralization.

CONCLUSIONS

Laminin 1 may be a marker for odontogenic epithelium. Additionally, laminin 5 may be involved in ghost cell formation and initiation of calcification.

Calcifying epithelial odontogenic tumor: an immunohistochemical case study

Calcifying epithelial odontogenic tumor (CEOT) is a rare benign odontogenic tumor. A case of CEOT in a 25-year-old female is presented here. Histologically, the case showed sheets of polyhedral epithelial cells with deep eosinophilic cytoplasm and prominent nuclei. Nuclear pleomorphism and hyperchromatism were evident. Globules of amyloid-like material among the tumor cells were prominent. Also found was a small area demonstrating a cribriform pattern. Immunohistochemical studies with antibodies against basement membrane proteins (laminins 1 and 5, collagen type IV and fibronectin), pan-cytokeratins AE1/AE3, vimentin, S-100 protein and CD 1a were performed. Tumor cells expressed laminins 1 and 5, fibronectin, cytokeratins and vimentin. The amyloid-like material was not reactive to all antibodies examined. A number of dendritic cells among sheets of tumor cells were revealed with strong staining for S-100 protein and CD 1a. These dendritic cells are likely to be Langerhans cells. Hence, immunohistochemistry is a useful method to study the variant of CEOT.

Malignant calcifying epithelial odontogenic tumor of the mandible: report of a case with pulmonary metastasis showing remarkable response to platinum derivatives

We describe a case of CEOT of the mandible, which underwent malignant transformation and developed metastatic tumors of the lung after repeated local recurrence. The primary tumor revealed typical histological features of benign CEOT showing sheets of polyhedral epithelial cells associated with abundant eosinophilic amyloid-like materials. On the other hand, the locally recurrent tumors had malignant features, such as increased nuclear pleomorphism with frequent mitotic figures and vascular invasion of tumor cells, as well as increased proliferative activity assessed by immunostaining for Ki-67. Chemotherapy was carried out against the pulmonary metastatic lesions, which showed a drastic response after 3 courses of intravenous administration of cisplatin (CDDP). To date, a total of 6 courses of CDDP and 6 courses of nedaplatin (CDGP) have been done, and the remaining pulmonary tumors have been dormant. This suggests that platinum derivatives could be a chemotherapeutic agent of choice against this rare tumor.

Molecular pathology of odontogenic tumors

Odontogenic tumors are lesions derived from the elements of the tooth-forming apparatus and are found exclusively within the jawbones. This review represents a contemporary outline of our current understanding of the molecular and genetic alterations associated with the development and progression of odontogenic tumors, including oncogenes, tumor-suppressor genes, oncoviruses, growth factors, telomerase, cell cycle regulators, apoptosis-related factors, regulators of tooth development, hard tissue-related proteins, cell adhesion molecules, matrix-degrading proteinases, angiogenic factors, and osteolytic cytokines. It is hoped that better understanding of related molecular mechanisms will help to predict the course of odontogenic tumors and lead to the development of new therapeutic concepts for their management.

Analysis of amelogenin gene (AMGX, AMGY) expression in ameloblastoma

Although the amelogenin gene is expressed in ameloblastoma, the precise expression pattern of X and Y amelogenin genes (AMGX, AMGY) in this tumor has not yet been identified. In this study, we analyzed amelogenin gene expression in 19 samples (9 male, 10 female) of oral ameloblastomas by RT-PCR and detect the chromosomal origin of amelogenin mRNA by restriction enzyme digestion of the RT-PCR product. All tumor samples expressed amelogenin mRNA. We could detect increased level of AMGY expression in all male samples, higher than that of AMEX. It is an interesting finding as in normal male tooth development, the expression of AMGY is very much lower than that of AMGX. We postulate that epigenetic change of sex chromosomes may have some correlations with tumorigenesis of ameloblastoma. We also discuss the other possible mechanisms and points for future studies on this change in expression pattern.

Expression of enamel proteins and LEF1 in adamantinomatous craniopharyngioma: evidence for its odontogenic epithelial differentiation

AIMS

Adamantinomatous craniopharyngioma (ACP) resembles histologically some odontogenic tumours, such as ameloblastoma and calcifying odontogenic cyst. However, there has been no evidence that ACP differentiates also functionally as odontogenic epithelium. The aim of this study was to gain evidence of odontogenic epithelial differentiation in ACP by means of immunohistochemistry. Among normal human tissues, enamel proteins are expressed exclusively in teeth, and lymphoid enhancer factor 1 (LEF1), in co-operation with beta-catenin, play an important role in tooth development. The expression of these proteins is therefore indicative of odontogenic epithelial differentiation.

METHODS AND RESULTS

The expression of enamel proteins and LEF1 was examined in 10 adamantinomatous and six papillary craniopharyngiomas. All the ACPs showed a variable degree of enamel protein expression, including amelogenin, enamelin and enamelysin, mainly in ghost cells. LEF1 was also heterogeneously expressed in ACPs; remarkably, its expression pattern was identical to that of nuclear beta-catenin accumulation. In contrast, none of the papillary craniopharyngiomas expressed enamel proteins or LEF1.

CONCLUSIONS

These results suggest that ACP consistently shows odontogenic epithelial differentiation. Since ACPs harbour beta-catenin mutation, the inappropriate activation of beta-catenin/LEF1 complex-dependent transcription may play a critical role in ACP tumorigenesis.

Ameloblastin gene (AMBN) mutations associated with epithelial odontogenic tumors

Ameloblastin (AMBN, MIM *601259) gene expresses an important protein (AMBN), present in the organic matrix of enamel. The AMBN protein has an important role in the differentiation of ameloblast cells and epithelium-mesenchyme signaling during odontogenesis which prompted us to investigate this gene in aggressive epithelial odontogenic tumors, such as ameloblastomas, and in some non-aggressive ones, such as the adenomatoid odontogenic tumor and the squamous odontogenic tumor. Six cases of epithelial odontogenic tumors were studied and normal cells of the patient's mucosa were used as negative controls. The results demonstrated novel mutations in all tumors, while mucosal cells showed the wild type DNA sequence. Our data demonstrates that AMBN gene has an important role in the tumorigenesis of subtypes of epithelial odontogenic tumors and that this phenotypic heterogeneity could be caused by genetic heterogeneity.

mRNA expression and phenotype of odontogenic tumours in the v-Ha-ras transgenic mouse

Ameloblastomas are the most common odontogenic neoplasia in humans, and although typically considered locally invasive and benign, frequently recur subsequent to surgical resection. The Tg.AC transgenic mouse carrying the v-Ha-ras oncogene has been found to spontaneously develop ameloblastoma-like tumours (35% by 1 year of age) that are rare in the wild type FVB background strain.

OBJECTIVE

The purpose of this study was to characterise the mRNA expression of genes in the mouse tumours that are either expressed in human ameloblastomas or essential for normal odontogenesis and to correlate the expression to the histological phenotype.

STUDY METHODS

Histological, immunohistochemical and RT-PCR studies were used to evaluate clinically demonstrable odontogenic tumours occurring spontaneously in seven Tg.AC v-Ha-ras transgenic mice (homozygous, at 7 months of age or heterozygous at 11 months of age).

RESULTS

Most genes profiled were expressed in all tumour samples, however three (amelogenin, matrix metalloproteinase-20 (MMP-20) and Dlx7) displayed differential expression. In addition, only the most highly differentiated tumour stained positively for collagen. In most cases, the variable expression could be explained by reference to the histological phenotype, although differences in gene expression were apparent within the Type 2 and the mixed phenotype tumours.

CONCLUSIONS

These data confirm that many of the genes thought to be important in odontogenesis and odontogenic tumour formation in humans are also expressed in these murine ameloblastoma-like tumours however genes associated with terminal differentiation of ameloblasts demonstrate differential expression between the tumour phenotypes.

Calcifying epithelial odontogenic (Pindborg) tumor-associated amyloid consists of a novel human protein

Calcifying epithelial odontogenic tumors (CEOTs), also known as Pindborg tumors, are characterized by the presence of squamous-cell proliferation, calcification, and, notably, amyloid deposits. On the basis of immunohistochemical analyses, the amyloidogenic component had heretofore been deemed to consist of cytokeratin-related or other molecules; however, its chemical composition had never been elucidated. We have used our microanalytic techniques to characterize the protein nature of CEOT-associated amyloid isolated from specimens obtained from 3 patients. As evidenced by the results of amino-acid sequencing and mass spectrometry, the fibrils were found to be composed of a polypeptide of approximately 46 mer. This component was identical in sequence to the N-terminal portion of a hypothetical 153-residue protein encoded by the FLJ20513 gene cloned from the human KATO III cell line. That the amyloid protein was derived from this larger molecule was demonstrated by reverse transcription-polymerase chain reaction amplification of tumor-cell RNA where a full-length FLJ20513 transcript was found. Furthermore, immunohistochemical analyses revealed that the amyloid within the CEOTs immunostained with antibodies prepared against a synthetic FLJ20513-related dodecapeptide. Our studies provide unequivocal evidence that CEOT-associated amyloid consists of a unique and previously undescribed protein that we provisionally designate APin.

Calcifying odontogenic cyst: clinicopathological features and immunohistochemical profile of 10 cases

BACKGROUND

Calcifying odontogenic cyst (COC) is an uncommon odontogenic lesion with few studies describing its immunohistochemical profile and proliferative activity reported in the literature.

METHODS

Clinical and histological features and immunohistochemical expression of cytokeratins, Mel-CAM (CD146), bcl-2, PCNA and ki-67, in 10 cases of COC were studied.

RESULTS

All 10 cases affected the maxilla, eight intraosseous and two peripheral. Five central cases were cystic and three were cystic associated with odontoma, and the two extraosseous showed solid histological pattern; immunohistochemistry was positive for cytokeratins 8, 14, 19, AE1/AE3 and 34betaE12 and bcl-2 in all cases, and Mel-CAM in six cases. Proliferative activity was greater in the epithelium of central cystic COC in relation to COC associated with odontoma and peripheral lesions.

CONCLUSION

Calcifying odontogenic cysts showed odontogenic cytokeratin profile and bcl-2 and Mel-CAM expression indicate that these proteins may be involved in the development of COC. There were no recurrences after surgery, irrespective of their proliferative activity.

Distribution of basement membrane type IV collagen alpha chains in ameloblastoma: an immunofluorescence study

BACKGROUND

Type IV collagen, a heterotrimeric molecule that exists in six genetically distinct forms, alpha1(IV)-alpha6(IV) is a major structural component of basement membrane (BM) and acts as a scaffold for other BM constituents.

METHODS

Indirect immunofluorescence using alpha chain-specific monoclonal antibodies was employed to clarify basement membrane (BM) collagen IV distribution in two ameloblastoma, and for comparison, on oral mucosa and tooth germ.

RESULTS

Ameloblastoma BM expressed five of six genetically distinct forms of collagen IV: alpha1(IV), alpha2(IV), alpha5(IV) and alpha6(IV) chains occurred as intense linear stainings without disruption around neoplastic epithelium, and this expression pattern was fundamentally similar to oral mucosa BM; alpha4(IV) expression was rare and occurred around nests of primitive tumor cells or potentially invasive sites. The tooth germ demonstrated a stage- and position-specific collagen IV distribution: the inner enamel epithelium BM expressed alpha1(IV), alpha2(IV), and alpha4(IV) except in the cuspal predentine region; and the outer enamel epithelium BM expressed alpha1(IV), alpha2(IV), alpha5(IV), and alpha6(IV) chains.

CONCLUSIONS

Results suggest that collagen IV alpha chain distribution in ameloblastoma BM plays an important role in tumor cytodifferentiation and progression.

Disturbed tooth eruption in osteopetrotic (op/op) mice: histopathogenesis of tooth malformation and odontomas

BACKGROUND

Odontoma-like structures are formed in the jaw bone of osteopetrotic (op/op) mice, which have a congenital deficiency in osteoclastic differentiation due to the absence of functional macrophage colony-stimulating factor (M-CSF).

METHODS

To clarify the histopathogenesis of tooth malformation and odontoma-like structures, a 2-year postnatal process of development of the op/op mandibular incisor was examined radiologically and histologically. At the same time, extracellular matrix (ECM) remodeling around tooth germs was analyzed immunohistochemically.

RESULTS

Abnormal forms of op/op tooth germ were noticeable even at 3 days after birth on a radiogram. Histologically, op/op mice were clearly distinguished by the disappearance of dental follicular space at 3 days. With aging, bone trabeculae, which were not remodeled, penetrated into op/op tooth germs and divided them into several daughter germs, which were recognized as odontomas. In mandibular incisor bodies, the immature ECM components, such as heparan sulfate proteoglycan and tenascin, were preserved diffusely in the dental papilla/pulp, which indicates that maturation of the stroma does not take place in op/op mandibular incisors.

CONCLUSION

The observation suggests that the disturbed morphogenesis of op/op tooth germs is functionally explained by the disordered immunolocalization of ECM molecules, and that the dental follicular space is essential for normal tooth development because it prevents bone penetration into the tooth germs.

Calcifying epithelial odontogenic tumor showing microscopic features of potential malignant behavior

Calcifying epithelial odontogenic tumor (CEOT) is a rare benign, but locally aggressive, odontogenic tumor, and only 2 cases of malignant CEOT are reported in the literature. We describe a case of an atypical CEOT that penetrates the blood vessels, invades bone, and perforates the cortical plates of the mandible. On histologic examination, it shows marked pleomorphism and numerous mitotic figures, including a tripolar mitotic figure. Proliferating activity was found to be 5 times higher than typical CEOTs as demonstrated by the proliferating index, Ki-67, and analyzed by a computerized image analysis system. The Ki-67 labeling index of this case was also compared to various previously reported benign and malignant neoplasms. Although there is no clinical finding of metastasis, we believe this neoplasm has malignant potential on the basis of the histologic features of vascular invasion, significant mitotic activity, atypical mitotic figures, and an increased proliferating index.

Neural cell adhesion molecule and neurothelin expression in human ameloblastoma

PURPOSE

The objective of the present study was to determine whether neural cell adhesion molecules (NCAM; CD56) and neurothelin (CD147) are expressed by adontogenic cells in the ameloblastoma.

MATERIALS AND METHODS

Frozen sections from ameloblastoma specimens (n = 7) were stained with monoclonal antibody-recognizing CD56 and CD147 molecules using indirect immunoperoxidase and indirect immunofluorescent techniques.

RESULTS

CD56 and CD147 molecules were strongly expressed by the peripheral columnar cells of the tumor nests. Neurothelin reactivity was also present in the stellate reticulum of the nests and in some stromal components.

CONCLUSIONS

The presence of these antigens in ameloblastoma supports the classic view about the neural crest origin of cells giving use to this tumor.

Tuftelin mRNA is expressed in a human ameloblastoma tumor

RT-PCR, Southern blotting and DNA sequencing have established for the first time that tuftelin mRNA is expressed in human ameloblastoma tumor. The expression of amelogenin mRNA in ameloblastoma was also established, confirming earlier reports by Snead et al. These results corroborate, on a molecular level, the enamel organ epithelial origin of ameloblastoma. In view of the present results, it is interesting that previous studies have indicated that although ameloblastoma, a non-mineralized odontogenic tumor, transcribes amelogenin mRNA, amelogenin (and enamelin) proteins are not expressed in this tissue. However, in mineralizing odontogenic tumors, both these classes of proteins are expressed.

Immunohistochemical detection and distribution of enamelysin (MMP-20) in human odontogenic tumors

Enamelysin is a tooth-specific protease that was initially isolated from porcine enamel organ and subsequently from human odontoblasts. Since this protease is thought to play important roles in tooth development, the evaluation of enamelysin in odontogenic tumors may aid our understanding of the histogenesis and cell differentiation of such lesions. A monoclonal antibody (203-1C7) was generated against synthesized human enamelysin oligopeptide and was used to assess the immunolocalization of enamelysin in healthy developing tooth germs and various types of odontogenic lesions. In tooth germs, enamelysin expression was detected only in the secretory enamel. Thus, 203-1C7 may serve as an enamel-specific marker in the late stage of enamel matrix development and calcification. In odontogenic lesions, strong enamelysin staining was demonstrated in the immature enamel matrix of ameloblastic fibro-odontomas and odontomas. Furthermore, enamelysin was also detected in globular amyloid masses and calcified foci in calcifying epithelial odontogenic tumors, hyaline droplets, small and large mineralized areas in adenomatoid odontogenic tumors, and a portion of ghost cells in calcifying odontogenic cysts. Positive reactivity was also observed in selected tumor cells in some of these tumors. No intracellular staining for enamelysin was detected in ameloblastomas or the ameloblastic portion of ameloblastic fibro-odontomas. Also, enamelysin was not detected in dentin, dysplastic dentinoid hyaline matrices, and cementum that were present within the tumors examined. Thus, taken together, our results suggest that the enamelysin-specific monoclonal antibody (203-1C7) may be utilized as a marker of early enamel development and that enamelysin may be involved in the pathogenesis of specific odontogenic tumors.

Ghost cells in calcifying odontogenic cyst express enamel-related proteins

The so-called ghost cell is a unique cell type occurring in a variety of odontogenic and non-odontogenic lesions. However, the true nature of ghost cells has not been determined. In the present study, we examined the immunoreactivity of ghost cells in calcifying odontogenic cysts and dermal calcifying epitheliomas, with antibodies against amelogenin, enamelin, sheath protein (sheathlin) and enamelysin, in an attempt to clarify the nature of this unique cell. The cytoplasm of ghost cells in calcifying odontogenic cysts demonstrated distinct immunolocalization of the enamel-related proteins, while similar in the calcifying epitheliomas of the skin showed a negative reaction. The results indicate that the ghost cells in calcifying odontogenic cysts, as opposed to ghost cells in dermal calcifying epitheliomas, contain enamel-related proteins in their cytoplasm accumulated during the process of pathological transformation.

Aberrant gene expression in epithelial cells of mixed odontogenic tumors

Comparative investigations of odontogenic cells in normally forming teeth and tumors may provide insights into the mechanisms of the differentiation process. The present study is devoted to late phenotypic markers of ameloblast and odontoblast cells, i.e., proteins involved in biomineralization. The in situ expression of amelogenins, keratins, collagens type III and IV, vimentin, fibronectin, osteonectin, and osteocalcin was performed on normal and tumor odontogenic human cells. The pattern of protein expression showed some similarities between ameloblasts and odontoblasts present in normally developing human teeth and cells present in neoplastic tissues of ameloblastic fibroma, ameloblastic fibro-odontomas, and complex odontomas. Amelogenins (for ameloblasts) and osteocalcin (for odontoblasts) were detected in cells with well-organized enamel and dentin, respectively. In contrast, "mixed" cells located in epithelial zones of mixed odontogenic tumors co-expressed amelogenins and osteocalcin, as shown by immunostaining. The presence of osteocalcin transcripts was also demonstrated by in situ hybridization in these cells. Keratins and vimentin were detected in the same epithelial zones. Tumor epithelial cells were associated with various amounts of polymorphic matrix (amelogenin- and osteocalcin-immunoreactive), depending on the types of mixed tumors. No osteocalcin labeling was found in epithelial tumors. This study confirms that the differentiation of normal and tumor odontogenic cells is accompanied by the expression of some common molecules. Furthermore, the gene products present in normal mesenchymal cells were also shown in odontogenic tumor epithelium. These data may be related to a tumor-specific overexpression of the corresponding genes transcribed at an undetectable level during normal development and/or to an epithelial-mesenchymal transition proposed to occur during normal root formation. A plausible explanation for the results is that the odontogenic tumor epithelial cells are recapitulating genetic programs expressed during normal odontogenesis, but the tumor cells demonstrate abnormal expression patterns for these genes.

Amelogenin expression in canine oral tissues and lesions

Amelogenins are major enamel proteins within the enamel extracellular matrix. The expression of amelogenin was confirmed in neonatal tissues of the canine jaw. The sequence of a portion of canine amelogenin cDNA, within exons 5 and 6, was determined and found to be closely homologous to sequences reported in the cow, pig, mouse and human being. Two acanthomatous epulides collected from clinically affected dogs showed amelogenin expression, whereas 22 other canine oral lesions, including six additional acanthomatous epulides, did not show amelogenin expression. Examination of structural proteins may allow precise identification of the histogenesis of the odontogenic neoplasms, which are often difficult to distinguish by means of morphological criteria alone.

Establishment of ameloblastoma cell line, AM-1

Ameloblastomas are slowly growing, locally invasive neoplasms with a potentially destructive behaviour. The molecular mechanisms that regulate the cell growth and invasion of ameloblastoma cells are unknown. Because ameloblastoma cells placed in culture have a very limited lifespan, the establishment of immortalized clones of ameloblastoma cells would aid its study. We produced an immortalized ameloblastoma cell line (AM-1) using human papillomavirus type-16. This cell line maintains epithelial cell morphology and expresses cytokeratins K8, K14, K18, K19. Furthermore, bcl-2 protein, which prevents apoptosis, is expressed. We investigated the behaviour of these cells on a collagen matrix in vitro. These cells grew in a monolayer over foci of collagen degradation and could invade the collagen gel at such sites. Since the behavior of cell line AM-1 mimics the behavior of ameloblastoma in vivo, it may be a valuable model for the study of these neoplasms.