Immunohistochemical expression of amelogenins in odontogenic epithelial tumours and cysts

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.

Analysis of Protein Immunoexpression and Its Interrelationship in the Pathogenesis of Odontomas and Ameloblastic Fibro-Odontomas: A Systematic Review

Odontomas and ameloblastic fibro-odontomas (AFOs) are the result of a developmental anomaly of odontogenic tissues. A literature review of proteins immunoexpressed in odontomas and AFOs was conducted in order to determine which proteins are involved in the pathogenesis of these lesions. AFO was changed to early odontoma in the 2017 WHO classification and will also be discussed in this article. A literature search was performed in the following electronic databases: PubMed/MEDLINE, Web of Science, Scopus, EMBASE, Lilacs, Cochrane Collaboration Library, and Science Direct. The research question was developed according to the population, intervention, comparison, and outcome (PICO) framework: Which proteins are related to the differentiation of odontomas and what is their interrelationship with AFOs? Thirty articles met all inclusion criteria and were selected for this systematic review, totaling 355 cases of odontomas and 43 cases of AFO. Similar immunoexpression was observed in odontomas and AFOs. Immunoexpression of proteins involved in cell differentiation was higher in compound odontomas than in complex odontomas. Proteins involved in histodifferentiation and enamel formation were more frequent in odontomas. The immunoexpression of enamel matrix proteins differs between odontomas and tooth germs, with their persistence being related to the development of odontomas. Compound odontomas exhibit the highest immunoexpression of proteins involved in cellular histodifferentiation and the Wnt/beta-catenin pathway is involved in tumor formation.

Ghost cell characterization in calcifying odontogenic cysts and dentinogenic ghost cell tumors: An immunohistochemical study

OBJECTIVES

The aim of our study was to ascertain the true nature of ghost cells (GCs) by immunolocalization of cytokeratin (CK) 6, CK19, and amelogenin in calcifying odontogenic cysts (COCs) and dentinogenic ghost cell tumors (DGCTs) in an attempt to determine the nature of this unique cell.

METHODS

A total of thirteen cases (six COCs and seven DGCTs) were examined immunohistochemically, in order to compare immunoreactivity for CK6, CK19, and amelogenin in odontogenic GCs.

RESULTS

Positive expression of amelogenin (92.3%) and CK6 (77%) was chiefly found in GCs. CK19 expression was observed in the cytoplasm of odontogenic epithelial cells of the lining epithelium. GCs were devoid of CK19 expression and were positive only on the cytoplasmic periphery.

CONCLUSION

In the current study, GCs showed accumulation of amelogenin and hard keratins in their cytoplasm during pathological transformation.

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.

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.

Primordial odontogenic tumor: An immunohistochemical profile

BACKGROUND

Primordial Odontogenic Tumor (POT) is a recently described odontogenic tumor characterized by a variably cellular loose fibrous tissue with areas similar to the dental papilla, covered by cuboidal to columnar epithelium that resembles the internal epithelium of the enamel organ, surrounded at least partly by a delicate fibrous capsule. The purpose of this study was to investigate the possible histogenesis and biological behavior of this rare tumor by means of a wide immunohistochemical analysis of its epithelial and mesenchymal components.

MATERIAL AND METHODS

The immunoexpression of twenty-three different antibodies were evaluated in four cases of POT.

RESULTS

The epithelial cells that cover the periphery of the tumor showed immunopositivity for Cytokeratins 14 and 19, while Amelogenin, Glut-1, MOC-31, Caveolin-1. Galectin-3, PITX2, p53, Bax, Bcl-2, Survivin and PTEN were variably expressed in focal areas. The mesenchymal component of the tumor was positive for Vimentin, Syndecan-1, PITX2, Endoglin (CD105), CD 34, Cyclin D1, Bax, Bcl-2, Survivin and p53. PTEN and CD 90 showed a moderate positivity. BRAF V600E and Calretinin were negative in all samples. Cell proliferation markers (Ki-67, MCM-7) were expressed in <5% of the tumor cells.

CONCLUSIONS

According to these immunohistochemical findings, we may conclude that POT is a benign odontogenic tumor in which there is both epithelial and mesenchymal activity during its histogenesis, as there is expression of certain components in particular zones in both tissues that suggests this tumor develops during the immature (primordial) stage of tooth development, leading to its inclusion within the group of benign mixed epithelial and mesenchymal odontogenic tumours in the current World Health Organization classification of these lesions.

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.

Current Concepts and Occurrence of Epithelial Odontogenic Tumors: II. Calcifying Epithelial Odontogenic Tumor Versus Ghost Cell Odontogenic Tumors Derived from Calcifying Odontogenic Cyst

Calcifying epithelial odontogenic tumors (CEOTs) and ghost cell odontogenic tumors (GCOTs) are characteristic odontogenic origin epithelial tumors which produce calcifying materials from transformed epithelial tumor cells. CEOT is a benign odontogenic tumor composed of polygonal epithelial tumor cells that show retrogressive calcific changes, amyloid-like deposition, and clear cytoplasm. Differentially, GCOTs are a group of transient tumors characterized by ghost cell presence, which comprise calcifying cystic odontogenic tumor (CCOT), dentinogenic ghost cell tumor (DGCT), and ghost cell odontogenic carcinoma (GCOC), all derived from calcifying odontogenic cysts (COCs). There is considerable confusion about COCs and GCOTs terminology, but these lesions can be classified as COCs or GCOTs, based on their cystic or tumorous natures, respectively. GCOTs include ameloblastomatous tumors derived from dominant odontogenic cysts classified as CCOTs, ghost cell-rich tumors producing dentinoid materials as DGCTs, and the GCOT malignant counterpart, GCOCs. Many authors have reported CEOTs and GCOTs variably express keratins, β-catenin, BCL-2, BSP, RANKL, OPG, Notch1, Jagged1, TGF-β, SMADs, and other proteins. However, these heterogeneous lesions should be differentially diagnosed to allow for accurate tumor progression and prognosis prediction.

A histopathological and immunohistochemical analysis of ameloblastic fibrodentinoma

Ameloblastic fibrodentinoma (AFD) is considered a mixed odontogenic tumor that is characterized by conserved epithelial and ectomesenchymal neoplastic components. AFD is composed of long narrow cords and islands of odontogenic epithelium; the epithelial strands lie in a myxoid cell-rich ectomesenchymal tissue with stellate-shaped fibroblasts that exhibit long slender cytoplasmic extensions that resemble dental papilla. The lesions show the presence of dysplastic dentin. Although AFD is a rare entity and its very existence is not completely accepted, based on the extent of histodifferentiation, it is considered to represent a stage between ameloblastic fibroma and ameloblastic fibroodontoma. This study aimed to provide a histopathological and immunohistochemical characterization of this infrequent tumor. A large panel of antibodies including amelogenin, Ck 19, calretinin, syndecan-1, E-cadherin, MSH2, histone H3, and Ki-67 was used to illustrate the nature of the tumor.

Histopathologic diversity of Gorlin's cyst: a study of four cases and review of literature

AIM

The purpose of the present article is to discuss four different case reports of the so-called calcifying odontogenic cyst and highlight the histopathological diversity of the same.

BACKGROUND

Calcifying odontogenic cyst was first described by Gorlin et al in 1962. Ever since, its identification as a specific odontogenic lesion, controversies and confusions have existed regarding the relationship between cystic lesions and solid tumor masses that share cellular and histomorphologic features. Although several classifications were proposed, dilemma still persists regarding the nature of these lesions as cysts, neoplasms and even malignancies.

CONCLUSION AND CLINICAL SIGNIFICANCE

The classifications discussed for the so-called calcifying odontogenic cyst by various authors have only added to further confusion rather than enlightening. Though many authors state that classifications remain only an academic exercise, it definitely has significance in treatment planning. Emphasis should, therefore, be laid on a universally accepted classification.

Biochemical and immunohistochemical characterization of the amyloid in canine amyloid-producing odontogenic tumor

The amyloid of canine amyloid-producing odontogenic tumor (APOT) was evaluated biochemically and immunohistochemically. The N-terminal amino-acid sequence of purified amyloid protein from a canine APOT was strikingly similar to the sequence in both rat ameloblastin and porcine sheathlin. Immunohistochemically, the amyloid in APOT from 9 dogs was strongly reactive with anti-rat ameloblastin, anti-porcine sheathlin, and anti-canine APOT amyloid and weakly reactive with anti-porcine amelogenin but negative for antibodies to cytokeratins, vimentin, desmin, alpha-smooth muscle actin, amyloid A, glial fibrillary acidic protein, or S100 protein. The neoplastic epithelial cells of APOT were focally reactive with antibodies to ameloblastin, sheathlin, amelogenin, and canine APOT amyloid. The similarity in amino-acid sequence of the amyloid protein of canine APOT to that of enamel proteins, such as ameloblastin, sheathlin, and amelogenin, and the expression of these antigens in both APOT amyloid and in the neoplastic cells suggest that the amyloid of canine APOT is derived from enamel proteins secreted by ameloblasts.

Administration of the bisphosphonate zoledronic acid during tooth development inhibits tooth eruption and formation and induces dental abnormalities in rats

Bisphosphonates (BPs) are potent inhibitors of osteoclastic bone resorption and widely used for the treatment of osteoporosis and metastatic bone diseases. Recently, BPs have also been shown to benefit children with primary and secondary osteoporosis, including osteogenesis imperfecta; however, their long-term safety has not been established yet. Clinical and experimental studies have demonstrated that BPs delay or inhibit tooth eruption. The failure of tooth eruption causes several dental abnormalities. In this study, to determine the effects of BPs on tooth formation, the BP zoledronic acid (ZOL) was injected into 7- and 14-day-old rats, and the development of the mandibular teeth was examined. X-ray analysis demonstrated that ZOL inhibited the eruption of both incisors and molars and their formation, especially in the molar roots. Histological examination showed that, in ZOL-treated animals, alveolar bone remained unresorbed around tooth crowns, which injured ameloblasts and enamel matrix, leading to defects of the enamel. Furthermore, haphazard proliferation of odontogenic epithelium and mesenchyme associated with primitive tooth structures, which resembles human odontomas, was induced at the basal end of incisors but not around the molars. Tooth ankylosis to alveolar bone was occasionally observed in molars. These results suggest that administration of BPs during tooth development has the potential to inhibit tooth eruption and formation and to induce several types of dental abnormalities, which may be attributed to the altered osteoclastic activities.

[Maxillary and mandibular carcinogenesis: research and prospects]

Development and growth of odontogenic tumours depend on impairment of numerous genes and molecules. In recent years, most of the genes involved in dental development were identified. This produced a new basis for the study of oral pathology and maxillofacial carcinogenesis. A better understanding of these molecular phenomena should allow to better determine the evolution of such lesions. Research breakthroughs should facilitate the development of new molecular and genetic therapeutic perspectives.

Analysis of ghost cells in calcifying cystic odontogenic tumors by confocal laser scanning microscopy

OBJECTIVE

The confocal laser scanning microscope represents an effective tool for studying biological samples stained for fluorescence observation. In this study we have used the confocal microscope to analyze ghost cells in calcifying cystic odontogenic tumors.

STUDY DESIGN

Specimens from 15 calcifying cystic odontogenic tumor cases were stained with hematoxylin and eosin, and scanned by a confocal laser scanning microscope to generate optically sectioned images.

RESULTS

All of the analyzed samples presented autofluorescent cells that were identified as ghost cells. The degree of autofluorescence intensity was variable and may be a result of the presence of hard keratin.

CONCLUSION

The confocal laser scanning microscope may be of help in analyzing and defining the nature and extent of keratinization processes in calcifying cystic odontogenic tumor ghost cells.

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.

Peripheral clear cell variant of calcifying epithelial odontogenic tumor: Report of a case and immunohistochemical investigation

A case of peripheral calcifying epithelial odontogenic tumor, clear cell variant, located on the right gingival maxilla of a 48-year-old woman, presenting as a 2.0-cm solitary, firm nodule was studied. Microscopically, it was composed of polyhedral and clear epithelial cells associated with amyloid-like deposition. The clear epithelial cells exhibited granules that were positive for periodic acid-Schiff, and the amyloid-like deposit stained with Congo red showed a green birefringence in the polarized light. Polyhedral and clear epithelial cells were immunopositive for AE1/AE3 and cytokeratin 14. Immunoexpression of fibronectin and types I and III collagen were different between the amyloid-like deposits and the connective tissue stroma. Tenascin surrounded epithelial cells located inside the amyloid-like deposits. Laminin and type IV collagen were immunodetectable around the strands, cords, and nests of epithelial cells. This report represents the seventh case of peripheral calcifying epithelial odontogenic tumor, clear cell variant.

Calcifying epithelial odontogenic (Pindborg) tumor with malignant transformation and metastatic spread

BACKGROUND

Pindborg tumors (calcifying epithelial odontogenic tumors) are uncommon neoplasms of odontogenic origin most often located in the posterior mandible. First described in detail in 1955 by Pindborg, these tumors are considered benign but can be locally aggressive in nature, with recurrence rates of 10% to 15% reported. The malignant form of this tumor is exceedingly rare.

METHODS

We describe the case of a 64-year-old woman initially treated for a painful infected left mandibular third molar. The patient underwent extraction of the tooth and excision of an associated soft tissue component. Subsequent histologic review identified a Pindborg tumor of the left posterior mandible.

RESULTS

After initial excision, this tumor recurred twice, with the recurrences exhibiting a progression to a malignant Pindborg tumor (odontogenic carcinoma) with vascular invasion and spread to a cervical lymph node. Further treatment involved radical surgery and adjuvant radiotherapy. At last review 12 months after treatment, the patient was disease free.

CONCLUSIONS

This article describes only the second case of odontogenic carcinoma. The transformation from benign to malignant histologic findings has not previously been documented in this tumor. The salient clinical features of this case are presented along with supportive pathologic and radiologic evidence.

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.

Clear cell odontogenic carcinoma. Report of two cases and review of the literature

This study reviews the literature and reports on the morphologic and immunophenotypic features of 2 clear cell odontogenic carcinomas occurring in the mandible of elderly women, showing extensive infiltration into adjacent tissues. The tumor cells were large, with clear cytoplasm, and arranged in irregular sheets. Some of the latter demonstrated a peripheral rim of cells with eosinophilic cytoplasm or included duct-like structures. There was no evidence of ameloblastic differentiation. Most cells contained glycogen granules and were immunoreactive for cytokeratins and epithelial membrane antigen. In the differential diagnosis other clear cell odontogenic, salivary gland, and metastatic tumors should be considered. Both cases were treated with surgical excision, and the patients are free of disease after 3 and 5 years, respectively. In the literature, however, variable behavior of these tumors has been reported, including recurrence and metastases. It is recommended that terms such as clear cell ameloblastoma and clear cell odontogenic tumor not be used to describe such tumors.

Cloning and characterization of the human ameloblastin gene

We isolated the full-length human ameloblastin (AMBN) cDNA clone using reverse transcription-polymerase chain reaction (RT-PCR) methods. Sequence analysis of the AMBN cDNA revealed an open reading frame of 1341bp encoding a 447-amino-acid protein. Comparison with pig, cattle, rat, and mouse AMBN sequences showed a high amino acid sequence similarity and led to the identification of a novel 78bp (26 amino acids) insert resulting from internal sequence duplication. By DNA analysis of a human genomic clones, the AMBN gene was shown to consist of 13 exons and a novel 78bp segment, which proved to comprise two small exons. Human ameloblastomas express AMBN transcripts that contain some mutations.

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.

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.

Characterization of novel monoclonal antibodies raised against formalin-fixed, paraffin-embedded human ameloblastoma

To obtain monoclonal antibodies reactive with odontogenic but not other types of epithelium, mice were immunized with homogenates of fixed ameloblastoma tissues, and monoclonal antibodies Y4 and M11 were produced. Y4 reacted immunohistochemically with odontogenic epithelial components but not with those of squamous differentiation, while M11 reacted with odontogenic epithelial components and a part of keratotic epithelial tissues. Immunoglobulin isotypes of both antibodies were IgM as determined by Ouchterlony immunodiffusion and enzyme-linked immunosorbent assays. Western blotting revealed that the antigen recognized by Y4 had a molecular mass of approximately 66 kDa; however, the antigen reactive with M11 was not identified by Western blotting in spite of various attempts in changing reaction conditions. These antibodies may be beneficial to histological analyses of odontogenic tissues and their related lesions.

Non-calcifying Pindborg tumor with Langerhans cells

A rare case of calcifying epithelial odontogenic tumor (CEOT) devoid of calcification is reported with histochemical, immunohistochemical and electron microscopic studies. The tumor occurred intraosseously in the left maxillary canine and premolar region of a 58-year-old man. The tumor chiefly consisted of scattered small islands of epithelial cells in an abundant fibro-myxoid connective tissue stroma. Among the nests, there were many spherical bodies of eosinophilic substance for which non-AA amyloid and non-keratin or basal lamina-like natures were demonstrated histochemically and immunohistochemically. In some nests, there were a few, occasionally several, cells positive for S-100 protein. Ultrastructurally, Langerhans cells with indented nuclei and Birbeck's granules were seen among tumor cells. The prognostic significance of the paucity of calcification and the presence of Langerhans cells in CEOT of which this is only the second description is discussed.