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.

Expression of the Insulin-like Growth Factor-1 Receptor in Odontogenic Myxoma

Odontogenic myxoma (OM) is a rare mesenchymal tumour arising in the jaws. The origin and pathogenesis of OM is poorly understood. The aim of this study was to characterize OM by immunolocalization of certain antigens in the tumour that are relevant for cellular differentiation, migration and maintenance.

MATERIALS AND METHODS

Five OMs were immunohistochemically investigated for expression of nestin, CD133, podoplanin, and insulin-like growth factor 1 receptor (IGF-1R).

RESULTS

OM failed to react with antibodies applied in this study, with the exception of IGF-1R in tumour cells.

DISCUSSION

OM is a poorly characterized benign, invasive tumour of the jaws. The absence of stem cell marker in OM does not exclude possible temporary expression of these antigens during certain phases of tumour development. The identification of IGF-1R in OM is shared with numerous tumours and indicates the ability of these tumour cells to respond to growth factors.

DNA methyltransferase immunohistochemical expression in odontogenic tumours

BACKGROUND

Odontogenic tumours are a heterogeneous group of lesions formed from tissues that give rise to the tooth. DNA methylation, a covalent addition of a methyl group to the 5-carbon position of a cytosine nucleotide, is considered an important regulator of gene expression. The addition of the methyl radical is catalysed by DNA methyltransferases (DNMTs). Although some epigenetic studies have been conducted in odontogenic tumours, a study with the three types of DNMTs in several different members of this group is missing. This study analyses the expression of DNMTs in odontogenic tumours.

METHODS

Formalin-fixed and paraffin-embedded tissue samples of 20 ameloblastomas, 10 calcifying cystic odontogenic tumours, 10 calcifying epithelial tumours, 10 adenomatoid odontogenic tumours, 10 keratocystic odontogenic tumours, five ameloblastic fibromas, two ameloblastic fibro-odontomas, four central odontogenic fibromas, seven peripheral odontogenic fibromas and 10 odontogenic myxomas were included. Immunohistochemical expression of DNMT1, 3A and 3B was assessed using a semi-quantitative analysis, and also a correlation with p21, p27 and E-cadherin immunoexpression was made.

RESULTS

DNMT1, 3A and 3B were expressed in the nucleus and/or cytoplasm of all odontogenic tumours. DNMT1 expression was directly correlated with p27 expression in ameloblastomas.

CONCLUSION

The high expression of DNMTs in odontogenic tumour cells suggests methylation as an important mechanism for this group of tumours.

Calcifying Cystic Odontogenic Tumour: immunohistochemical expression of matrix metalloproteinases, their inhibitors (TIMPs and RECK) and inducer (EMMPRIN)

BACKGROUND

Calcifying cyst odontogenic tumour (CCOT) is a rare benign cystic neoplasm of odontogenic origin. MMPs are responsible for extracellular matrix remodelling and, together their inhibitors and inducer, determinate the level of its turnover in pathological processes, leading to an auspicious microenvironment for tumour development. Thus, our goal was to evaluate matrix metalloproteinases (MMPs-2, -7, -9 and -14), their inhibitors (TIMPs-2, -3, -4 and RECK) and its inductor (EMMPRIN) expression in CCOT.

MATERIALS AND METHODS

We used 18 cases of CCOT submitted to immunolocalization of the target proteins and analysed in both neoplastic odontogenic epithelial and stromal compartments.

RESULTS

All molecules evaluated were expressed in both compartments in CCOT. In epithelial layer, immunostaining for MMPs, TIMPs, RECK and EMMPRIN was found in basal, suprabasal spindle and stellate cells surrounding ghost cells and ghost cells themselves, except for MMP-9 and TIMP-2 which were only expressed by ghost cells. In stromal compartment, extracellular matrix, mesenchymal (MC) and endothelial cells (EC) were positive for MMP-2, -7, TIMP-3 and -4, while MMP-9, TIMP-2 and RECK were positive only in MC and MMP-14 only in EC. Statistical significance difference was found between both compartments for MMP-9 (P < 0.001), RECK (P = 0.004) and EMMPRIN (P < 0.001), being more expressed in epithelium than in stroma. Positive correlation between both stromal EMMPRIN and RECK expression was found (R = 0.661, P = 0.003).

CONCLUSIONS

We concluded that these proteins/enzymes are differentially expressed in both epithelium and stroma of CCOT, suggesting an imbalance between MMPs and their inducer/inhibitors may contribute on the tumour behaviour.

Increased expression of autophagy-related proteins in keratocystic odontogenic tumours: its possible association with growth potential

The aim of this study was to evaluate the activation status of autophagy in keratocystic odontogenic tumours (KCOT), and to investigate its possible association with growth potential. We detected the expression of some key autophagy-related proteins in clinical samples of KCOT and radicular cysts and compared then by real-time quantitative polymerase chain reaction (qPCR) and immunohistochemical analysis, respectively. The correlation between the autophagy-related proteins tested, and with cell antiapoptotic (Bcl-2) or proliferative (Ki-67) markers in KCOT was explored using Spearman's rank correlation, followed by cluster analysis. The results showed that both the expression of mRNA and the immunoreactivity of the autophagy-related proteins tested were considerably increased in samples of KCOT compared with those in samples of radicular cysts. The correlation analyses showed that the immunostains of autophagy-related proteins in samples of KCOT correlated closely with each other. The immunostains of these autophagy-related proteins also correlated closely with the immunostains of Bcl-2 and Ki-67 in KCOT. More importantly, double-labelling immunofluorescence analyses also showed that the distribution of autophagic and proliferative markers was partially synchronous in samples from KCOT. We have, to our knowledge for the first time, implicated the activation of autophagy in KCOT, and showed its possible association with growth potential.

Benign odontogenic tumors versus histochemically related tissues: preliminary results from mid-infrared and solid-state nuclear magnetic resonance spectroscopy

Three types of human odontogenic tumors histologically classified as compound composite odontoma, ossifying fibroma, and Pindborg tumor were characterized using mid-infrared spectroscopy (mid-IR) and solid-state nuclear magnetic resonance (ssNMR). For comparison, human jawbone and dental mineralized tissues such as dentin, enamel, and dental cement were also characterized. The studies focused on the structural properties and chemical composition of pathological tissues versus histochemically related tissues. All analyzed tumors were composed of organic and mineral parts and water. Apatite was found to be the main constituent of the mineral part. Various components (water, structural hydroxyl groups, carbonate ions (CO(3)(2-)), and hydrogen phosphate ions (HPO(4)(2-))) and physicochemical parameters (index of apatite maturity and crystallinity) were examined. The highest organic/mineral ratio was observed in fibrocementoma, a finding that can be explained by the fibrous character of the tumor. The lowest relative HPO(4)(2-) content was found in odontoma. This tumor is characterized by the highest mineral crystallinity index and content of structural hydroxyl groups. The Pindborg tumor mineral portion was found to be poorly crystalline and rich in HPO(4)(2-). The relative CO(3)(2-) content was similar in all samples studied. The results of spectroscopic studies of odontogenic tumors were consistent with the standard histochemical analysis. It was shown that the various techniques of ssNMR and elaborate analysis of the mid-IR spectra, applied together, provide valuable information about calcified benign odontogenic tumors.

Expression of podoplanin in nevoid basal cell carcinoma syndrome-associated keratocystic odontogenic tumours

BACKGROUND

Keratocystic odontogenic tumour (KCOT) is a benign oral neoplasm of odontogenic origin. The majority of KCOT develop sporadically. The main differential diagnosis of KCOT is from other odontogenic cysts and ameloblastoma. In the rare nevoid basal cell carcinoma syndrome (NBCCS, synonym: Gorlin(-Goltz)-Syndrome), however, KCOTs are frequently detected and may be the initial sign of this clinical syndrome. Podoplanin is a mucin-type transmembrane protein found in podocytes of human kidneys homologous to T1α-2. The expression of podoplanin in some other non-endothelial tissues raised our interest in studying this antibody in tissues of odontogenic origin. Recently, we reported podoplanin expression in sporadic cases of KCOT. We intended to investigate the podoplanin expression in KCOTs associated with NBCCS.

MATERIALS AND METHODS

Archival paraffin embedded tissues from six KCOTs from patients with known NBCCCS were analyzed immunohistochemically with antibodies to podoplanin (D2-40) and p63.

RESULTS

We observed a continuous linear immunoreactivity of basal epithelial cells for podoplanin in all cases. The staining intensity was strong and did not differ from that for KCOT in previously reported sporadic cases. Strong nuclear P63 expression was detected in basal cell layers and diminished in suprabasal layers.

CONCLUSION

KCOTs exhibited enhanced podoplanin expression in a clinical setting of NBCCS. Although the biological functions of podoplanin have not yet been fully recognized, the overexpression of this protein is capable of promoting the formation of elongated cell extensions, and increasing adhesion and migration of inflammatory cells. Podoplanin expression in KCOT is possibly associated with slow invasion of the adjacent structures and the well-known frequent local tumour recurrences of this odontogenic tumour.

Characterization of Apin, a secreted protein highly expressed in tooth-associated epithelia

We previously reported expression of a protein by enamel organ (EO) cells in rat incisors, originally isolated from the amyloid of Pindborg odontogenic tumors called Apin. The aim of the present study was to further characterize the Apin gene and its protein in various species, assess tissue specificity, and clarify its localization within the EO. Northern blotting and RT-PCR revealed that expression of Apin was highest in the EO and gingiva, moderate in nasal and salivary glands, and lowest in the epididymis. The protein sequences deduced from the cloned cDNA for rat, mouse, pig, and human were aligned together with those obtained from four other mammal genomes. Apin is highly conserved in mammals but is absent in fish, birds, and amphibians. Comparative SDS-PAGE analyses of the protein obtained from bacteria, transfected cells, and extracted from EOs all indicated that Apin is post-translationally modified, a finding consistent with the presence of predicted sites for phosphorylation and O-linked glycosylation. In rodent incisors, Apin was detected only in the ameloblast layer of the EO, starting at post-secretory transition and extending throughout the maturation stage. Intense labeling was visible over the Golgi region as well as on the apices of ameloblasts abutting the enamel matrix. Apin was also immunodetected in epithelial cells of the gingiva which bind it to the tooth surface (junctional epithelium). The presence of Apin at cell-tooth interfaces suggests involvement in adhesive mechanisms active at these sites, but its presence among other epithelial tissues indicates Apin likely possesses broader physiological roles.

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.

KAI-1 protein expression in odontogenic cysts

The KAI-1 tumor suppressor gene is widely distributed in normal tissues and its down-regulation may be correlated with the invasive phenotype and metastases in several different epithelial tumors. The aim of the present study was an evaluation of KAI-1 expression in radicular cysts (RC), follicular cysts (FC), orthokeratinized keratocysts (OOKC), and parakeratinized keratocysts (POKC). Eighty-five odontogenic cysts, 28 RC, 22 FC, and 35 OKC (16 OOKC, 19 POKC) were selected. All the POKC were negative and only four of 16 of the OOKC were positive for KAI-1. On the contrary, all RC and FC cases were positive and immunoreactivity for KAI-1 was detected throughout all the layers of the cyst epithelium. The lack of KAI-1 expression in POKC could help to explain the differences in the clinical and pathologic behavior of OKC and, according to what has been reported for epithelial tumors, could be related to the increased aggressive behavior and invasiveness of OKC.

Odontogenic Myxoma: A Clinicopathologic Study of 25 Cases

Context.—Odontogenic myxoma is an uncommon tumor that has the potential for extensive destruction of the jaws.

Objective.—To document the clinical, pathologic, and behavioral features of odontogenic myxomas.

Design.—Histologic and immunocytochemical examinations were performed on odontogenic myxomas from 25 Chinese patients. Clinical and available follow-up data were analyzed.

Results.—In the present series, 13 were male and 12 female. The age at diagnosis ranged from 6 to 66 years, with a mean age of 28.8 years. Twelve tumors involved the mandible and 13 occurred in the maxilla, with a predilection for posterior areas. The posterior maxillary tumors frequently (9/10) involved the maxillary sinus. Of the 23 cases with radiographic records, 22 lesions presented with a multilocular appearance. Although 80% of the mandibular lesions showed a well-defined border, only 33.3% of the maxillary tumors were well-defined. Histologically, odontogenic myxomas were mainly composed of spindled or stellate-shaped cells in a mucoid-rich intercellular matrix. Tumors containing noticeable fibrous components were evident in 13 cases. Apart from 5 cases treated conservatively by enucleation, the remaining 20 cases were treated by relatively radical procedures, including block/segmental resection and partial or total maxillectomy or mandibulectomy. Follow-up data were available on 22 patients and only 1 patient initially treated by enucleation had a recurrence.

Conclusions.—Odontogenic myxomas have a very bland histologic appearance that lacks atypia and may easily lead to misdiagnosis. The tumors are infiltrative with no capsulation and may recur after inadequate surgery.

Nestin expression in odontoblasts and odontogenic ectomesenchymal tissue of odontogenic tumours

BACKGROUND

Nestin, one of the intermediate filaments constituting the cytoskeleton, is a marker of neural stem cells or progenitor cells. Its expression is also related to tooth development and repair of dentine.

AIMS

The aim of this study was to investigate nestin expression in various odontogenic tumours and evaluate its usefulness for histopathological diagnosis.

METHODS

We studied formalin fixed, paraffin embedded specimens from 129 cases of odontogenic tumours and 9 of mandibular intraosseous myxoma. After characterisation of odontogenic ectomesenchymal tissues in these tumours using antibodies to vimentin, desmin, neurofilament, and glial fibrillary acidic protein, we immunohistochemically examined nestin expression.

RESULTS

No differentiation towards muscle and nervous tissues was found in the odontogenic ectomesenchymal tissues. Although almost all the ameloblastomas and malignant ameloblastomas were negative for nestin, odontogenic ectomesenchyme in the odontogenic mixed tumours demonstrated nestin immunolocalisation, particularly in the region adjacent to the odontogenic epithelium. Odontoblasts and their processes, pulp cells near the positive odontoblasts, and flat cells adhering to the dentine showed immunoreaction with nestin in the odontomas and odontoma-like component in the ameloblastic fibro-odontomas. Neoplastic cells in almost half cases of jaw myxoma and one case of odontogenic fibroma expressed nestin.

CONCLUSIONS

The distribution of nestin in the odontogenic mixed tumours suggests that nestin expression in the odontogenic ectomesenchyme is upregulated by stimulation from odontogenic epithelium. In addition, nestin may also be involved in the differentiation from pulp cells to odontoblasts in odontogenic tumours. Therefore, nestin is a useful marker for the odontogenic ectomesenchyme and odontoblasts in odontogenic tumours. Nestin, one of the intermediate filaments constituting the cytoskeleton, is a marker of neural stem cells or progenitor cells. Its expression is also related to tooth development and repair of dentine.

Odontogenic ghost cell tumour with clear cell components: clear cell odontogenic ghost cell tumour?

A case of odontogenic ghost cell tumour (OGCT) with clear cell components was encountered in the mandible of a 63-year-old man. The tumour revealed ameloblastomatous-type epithelial components accompanied by clusters of ghost cells and dentinoid juxtaposed to the odontogenic epithelium. In addition, some areas of the tumour tissue showed sheets and islands of clear, glycogen containing epithelial cells, which were separated by a thin fibrous connective tissue stroma. Both ameloblastic and clear cells exhibited positive immunoreactivities for cytokeratin 19 and AE1/3. It is not known whether this tumour represents a clear cell change of a pre-existing OGCT or a separate and distinct neoplasm derived de novo from the odontogenic epithelium. This tumour was given the term 'clear cell OGCT' because it captures the clear cell components, which is one of the most prominent distinguishing features of the tumour.

Differential distribution of glycosaminoglycans in human cementifying fibroma and fibro-osseous lesions

OBJECTIVE

Differential diagnosis of cementifying fibroma, ossifying fibroma and fibrous dysplasia by histological evaluation is often difficult. The aim of this study was to examine the immunoreactivities for keratan sulfate (KS) and chondroitin-4-sulfate (C4S) glycosaminoglycans of the histological samples obtained from mandibles of patients with these diseases.

MATERIALS AND METHODS

The samples were collected from three patients with cementifying fibroma, two with ossifying fibroma and three with fibrous dysplasia and were subjected to immunohistochemical analyses.

RESULTS

The results demonstrated that a significant immunoreactivity for KS was found in lacunae housing cells in the cementum-particles of cementifying fibromas, while both ossifying fibromas and fibrous dysplasias showed no significant immunoreactivity for KS. For C4S, while the former showed little immunoreactivity, the latter two cases exhibited intensive immunostaining in the pre- and poorly mineralized matrices.

CONCLUSIONS

These results suggest that cementifying fibromas could be distinguished from these fibro-osseous tumors by using immunohistochemical analysis for KS and C4S.

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.

Cytokeratins in epithelia of odontogenic neoplasms

Neoplasms and tumours related to the odontogenic apparatus may be composed only of epithelial tissue or epithelial tissue associated with odontogenic ectomesenchyme. The immunohistochemical detection of different cytokeratins (CKs) polypeptides and vimentin has made it easier to explain the histogenesis of many epithelial diseases. The present study aimed to describe the immunohistochemical expression of cytokeratins 7, 8, 10, 13, 14, 18, 19 and vimentin in the epithelial components of the dental germ and of five types of odontogenic tumours. The results were compared and histogenesis discussed. All cells of the dental germ were positive for CK14, except for the preameloblasts and secreting ameloblasts, in which CK14 was gradually replaced by CK19. CK7 was especially expressed in the cells of the Hertwig root sheath and the stellate reticulum. The dental lamina was the only structure to express CK13. The reduced epithelium of the enamel organ contained CK14 and occasionally CK13. Cells similar to the stellate reticulum, present in the ameloblastoma and in the ameloblastic fibroma, were positive for CK13, which indicates a nature other than that of the stellate reticulum of the normal dental germ. The expression of CK14 and the ultrastructural aspects of the adenomatoid odontogenic tumour probably indicated its origin in the reduced dental epithelium. Calcifying odontogenic epithelial tumour is thought to be composed of primordial cells due to the expression of vimentin. Odontomas exhibited an immunohistochemical profile similar to that of the dental germ. In conclusion, the typical IF of odontogenic epithelium was CK14, while CK8, 10 and 18 were absent. Cytokeratins 13 and 19 labelled squamous differentiation or epithelial cells near the surface epithelium, and CK7 had variable expression.

Immunolocalization of PTCH protein in odontogenic cysts and tumors

The human patched gene (PTCH) functions in both embryologic development and tumor suppression. PTCH mutations have been found in odontogenic keratocysts. However, the expression and localization of the protein product of the gene have not been determined in odontogenic tumors and cysts. We investigated 68 odontogenic lesions by immunohistochemistry, and compared their PTCH expression with that in basal cell carcinomas. All odontogenic lesions, including two keratocysts with truncating mutations, were positive for PTCH. Different types of lesions had different amounts of staining. Lack of staining was noted in the majority of basal cell carcinomas. Taken together, these data suggest that odontogenic keratocysts arise with heterozygous mutations of the PTCH gene.

Immunohistochemical detection of hepatocyte growth factor, transforming growth factor-β and their receptors in epithelial odontogenic tumors

BACKGROUND

Tumors derived from odontogenic epithelium exhibit considerable variation and are classified into several benign and malignant entities. To clarify the role of growth factors in oncogenesis, cytodifferentiation and progression of epithelial odontogenic tumors, expression of hepatocyte growth factor (HGF), transforming growth factor-beta (TGF-beta) and their receptors were analyzed in these tumors as well as in tooth germs.

METHODS

Specimens of five tooth germs, 34 ameloblastomas, three calcifying epithelial odontogenic tumors (CEOTs), two clear cell odontogenic tumors (CCOTs), five adenomatoid odontogenic tumors (AOTs), six calcifying odontogenic cysts (COCs) and six malignant ameloblastomas were examined immunohistochemically with the use of antibodies against HGF, TGF-beta and their receptors.

RESULTS

In tooth germs and epithelial odontogenic tumors, immunoreactivity for HGF and TGF-beta was detected in both epithelial and mesenchymal cells, while expression of their receptors was found only in epithelial cells. In tooth germs and main types of ameloblastomas, HGF and TGF-beta reactivity was marked in epithelial cells near the basement membrane, and their receptors were diffusely positive in most epithelial cells. In subtypes of ameloblastomas, reduced expression of HGF, c-Met and TGF-beta and increased reactivity for TGF-beta receptors were detected in keratinizing cells in acanthomatous ameloblastomas, and granular cells in granular cell ameloblastomas demonstrated little or no expression of HGF, TGF-beta or their receptors. As compared with main types of ameloblastomas, basal cell ameloblastomas showed high HGF reactivity, and desmoplastic ameloblastomas exhibited elevated reactivity for TGF-beta and its receptors. Neoplastic cells in CEOTs, AOTs and COCs showed reactivity for HGF, TGF-beta and their receptors. Elevated HGF and TGF-beta reactivity was found in pseudoglandular cells in AOTs, and high expression of their receptors was noted in ghost cells in COCs. Metastasizing ameloblastomas showed similar expression patterns of HGF, TGF-beta and their receptors to those of benign ameloblastomas, while CCOTs and ameloblastic carcinomas had increased HGF expression and low reactivity for TGF-beta and its receptors as compared with benign ameloblastomas.

CONCLUSIONS

Immunohistochemical localization of HGF, TGF-beta and their receptors in tooth germs and epithelial odontogenic tumors supports the hypothesis that HGF and TGF-beta act on epithelial cells via paracrine and autocrine mechanisms. Altered expression of the agents in these epithelial odontogenic tumors, especially subtypes of ameloblastomas, AOTs and COCs, suggests that HGF and TGF-beta signaling might affect differentiation of neoplastic odontogenic epithelial cells. Activated HGF/c-Met pathway and reduced TGF-beta signaling in CCOTs and ameloblastic carcinomas may be associated with the malignant potential of these epithelial odontogenic tumors.

Immunohistochemical localization of large chondroitin sulfate proteoglycan in odontogenic tumor

The present study investigated the localization of versican in odontogenic tumors by immunohistochemistry, using paraffin-embedded sections obtained from 27 patients with odontogenic tumors (17 ameloblastomas, 1 adenomatoid odontogenic tumor, 4 odontogenic keratocysts, 1 calcifying odontogenic cyst, 2 ameloblastic fibromas, and 2 malignant ameloblastomas). Deparaffinized sections were immersed in a buffered 1 : 1000 solution of an antibody, 5D5 (raised against a large chondroitin sulfate proteoglycan from bovine sclera), which mainly recognizes versican. All samples showed a positive reaction for versican in connective tissues, whereas positive staining of epithelial nests was observed in only some samples. The positive staining in epithelial nests was in areas showing stellate reticulum-like, cuboidal, columnar cells at the periphery, and tear-drop structures. These results indicated that versican might be involved in, at least in part, the morphogenesis of neoplastic epithelium and mesenchymal tissues in odontogenic tumors.

Clear cell odontogenic carcinoma

Clear cell tumours, in the head and neck region, are usually derived from salivary or odontogenic tissues, or may be metastatic. A few clear cells may be present in odontogenic cysts, while, odontogenic neoplasms composed predominantly of clear cells are quite rare. They include calcifying epithelial odontogenic tumours (CEOT), ameloblastoma and odontogenic carcinoma. Clear cell odontogenic tumour (CCOT) has been classified in the last WHO classification as a benign tumour, but it is now recognized as a more sinister lesion and current opinion is that CCOT should be designated as a carcinoma. These tumours are characterized by aggressive growth, recurrences, and metastatic disease. A recent review of the literature has yielded 30 cases of tumours with similar characteristics. These tumours have a peak incidence in the 5th-7th decades, with a female predilection. The anterior portions of the jaws, especially the mandible, are most frequently affected. The aggressive potential of these neoplasms is well documented by the extensive invasion of adjacent tissues, multiple recurrences and regional or distant metastases.

Clear cell odontogenic carcinoma: a clinicopathologic and immunocytochemical study of 5 cases

CONTEXT

Odontogenic tumor composed predominantly of clear cells is a rare neoplasm of the jaws that was initially designated as clear cell odontogenic tumor. Subsequent reports in the literature, however, all have indicated that this tumor exhibits an aggressive behavior characterized by infiltrative local growth, recurrence, or metastases.

OBJECTIVE

To ascertain the clinicomorphologic features and biologic behavior of this tumor group, we present 5 additional cases using the term clear cell odontogenic carcinoma.

DESIGN

Histologic and immunohistochemical examinations were performed on clear cell odontogenic carcinomas from 5 patients. Clinical and follow-up data were recorded, and the literature was reviewed.

RESULTS

The patients were 1 man and 4 women with an average age of 42.4 years at diagnosis. Three tumors occurred in the mandible and the other 2 in the maxilla. Four of the 5 cases occurred in the anterior or premolar areas of the jaws, appearing as poorly marginated radiolucencies. All cases consisted of islands and sheets of large clear cells and small basaloid cells with scanty eosinophilic cytoplasm, which were separated by thin, mature, fibrous septae. The tumors were unencapsulated and showed aggressive infiltration of the surrounding muscle and perineural tissues. Most of the clear cells contained cytoplasmic glycogen. Immunocytochemically, the tumor cells were positive for pan-keratin, cytokeratin 19, and epithelial membrane antigen, but were negative for vimentin, S100 protein, desmin, smooth muscle actin, human melanoma antigen (HMB-45), and alpha(1)-antichymotrypsin. Follow-up data showed 4 of 5 patients to have multiple local recurrences, and 1 of these 4 had submandibular lymph node metastasis and a fatal outcome due to uncontrollable tumor growth.

CONCLUSION

These results suggest that odontogenic clear cell neoplasms are at least low-grade malignancies and should be classified as carcinomas.

Pigmented intraosseous odontogenic carcinoma of the maxilla: a pediatric case report and differential diagnosis

We report a pigmented intraosseous odontogenic carcinoma of the maxilla occurring in a 6-year-old Japanese boy. Grossly, the tumor showed solid, gray-yellow, and markedly pigmented appearance. Histology showed neoplastic growths of atypical epithelial cells that occasionally contained melanin pigments. Melanocytes with dendritic processes were often found in the tumor cell clusters, and solitary or aggregated melanophages were scattered within the dense fibrovascular stroma. The tumor cells were diffusely positive for cytokeratins and epithelial membrane antigen, and focally positive for vimentin, neuron specific enolase, neurofilament protein, carcinoembryonic antigen, and amelogenin. Ultrastructural studies showed well-developed intercellular junctions, mainly desmosomes, and glycogen particles. In addition, some tumor cells contained melanosomes and/or a few neurosecretory granules. We consider that the present tumor suggests a close association of ectoderm, mesenchyma, and neuroectoderm in embryogenesis of the tooth, and can raise a diagnostic confusion with melanotic neuroectodermal tumor.

Enamel proteins and extracellular matrix molecules are co-localized in the pseudocystic stromal space of adenomatoid odontogenic tumor

In order to examine the functional differentiation of tumor cells of adenomatoid odontogenic tumor (AOT) as ameloblasts and to determine the participation of the extracellular matrix (ECM) in the formation of its characteristic histologic architecture, tissue samples from five cases of adenomatoid odontogenic tumor were examined by immunohistochemical staining for enamel proteins and ECM molecules. Amelogenin, enamelin, laminin, heparan sulfate proteoglycan, fibronectin, collagen type IV and type V were immunolocalized within the luminal space and along the inner rim of duct-like structures. Eosinophilic hyaline droplets within the whorled or rosette masses of tumor cells showed basically the same staining pattern as the luminal contents. High columnar tumor cells that formed duct-like structures were immunopositive for amelogenin, while the staining intensity decreased with flattening of the cells, which was a result of luminal growth. The findings suggest that the constituent cells of duct-like structures are differentiated once to ameloblasts but fail to mature further due instead to increased production of ECM molecules and due to their retention in the lumina. It is possible to regard these special structures in AOT as stromal pseudocysts.

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.

A novel cell line that retains the morphological characteristics of the cells and matrix of odontogenic myxoma

Little is known about the histogenesis of the human odontogenic myxoma or the relation between tumour cells and the matrix. In order to attempt to remedy this situation, we established and investigated a cell line derived from a human odontogenic myxoma. To our knowledge this is the first cell line derived from this tumour. The cell line, named Mix 1, preserved features of the tumour cells. Mix 1 cells expressed vimentin, type I collagen, fibronectin, tenascin and hyaluronic acid. Ultrastructural analysis of cells of the tumour and cell line demonstrated similarities, both containing Golgi apparatus, rough endoplasmic reticulum and mitochondria indicative of secretory cells. Ultrastructural analysis showed the matrix to be represented by bundles of collagen fibrils in the tumour, and by irregular filaments in cultures more than 60 days old. The Mix 1 cell line promises to be an excellent model for investigating the biology of the odontogenic myxoma.

Immunohistochemical and histochemical characterization of the mucosubstances of odontogenic myxoma: histogenesis and differential diagnosis

To discuss the dental origin of odontogenic myxoma and to provide further information for the differential diagnosis between this tumor and myxoid malignant fibrous histiocytoma (MFH) which occasionally occurs in jaw bones, the contents of glycosaminoglycans (GAGs) and proteoglycans (PGs) in the mucosubstances of 15 odontogenic myxomas, 5 myxoid MFH and 3 human fetal tooth germs in the bell stage of development were characterized using histochemical and immunohistochemical methods. Histochemical staining of hyaluronic acid (HA) was undertaken using biotinylated HA binding protein (B-HABP), and immunohistochemical detection was done using a panel of antibodies against chondroitin 6-sulfate (CS-6), chondroitin 4-sulfate (CS-4), dermatan sulfate (DS), keratan sulfate (KS), heparan sulfate (HS), aggrecan, PG-M/versican, decorin and biglycan. In odontogenic myxoma, CS-6, HA and PG-M/versican were observed in the myxomatous matrix of all cases, while KS and HS were seen in none. As for CS-4, DS, aggrecan, decorin and biglycan, only irregular and mild stainings were shown. Consistent and strong positive straining for CS-6, HA and PG-M/versican were seen in dental papilla and provided evidence supporting the origin of this tumor from dental papilla. Except for the constant staining for HA, the myxoid matrix was rarely stained for most GAGs and PGs in myxoid MFH. Immunodetection of CS-6 and PG-M/version with the use of monoclonal antibodies 3-B-3 and 2-B-1 is therefore recommended as a useful tool in differentiating odontogenic myoma from myxoid MFH.

Expression of E-cadherin and alpha-catenin in epithelial odontogenic tumors: an immunohistochemical study

To clarify the possible role of cell adhesion in epithelial odontogenic tumors, expression of E-cadherin and alpha-catenin was examined by an immunohistochemical method. These molecules showed pericellular distribution in epithelial cells of the tooth germ and its derived tumors. In ameloblastomas, E-cadherin and alpha-catenin were expressed strongly in central polyhedral cells and slightly in peripheral columnar cells. These features resembled those of epithelial components in the tooth germ tissues, retaining cytodifferentiation of odontogenic epithelium. Expression of the molecules in the variants of ameloblastomas showed loss in the keratinizing areas and reduction in the granular cell clusters, suggesting terminal differentiation of the tumor cells. Calcifying epithelial odontogenic tumors and a clear cell odontogenic tumor preserved E-cadherin and alpha-catenin expression without a specific feature for histogenesis or cytodifferentiation. One case of two malignant ameloblastomas showed prominent reduction in expression of E-cadherin and alpha-catenin.

Clear cell variant of calcifying epithelial odontogenic tumor (CEOT) in the maxilla: report of a case with immunohistochemical and ultrastructural investigations

A rare case of clear cell variant of calcifying epithelial odontogenic tumor is presented with immunohistochemical and ultrastructural investigations. A 14-year-old Japanese girl was admitted with a complaint of swelling in the right posterior maxilla. Radiological examination showed a well-circumscribed radiolucent lesion located close to the impacted third molar. After only a partial tumor excision, the tumor recurred 13 years later. It appeared radiologically as an irregular radiodensity, and a subtotal maxillectomy was performed. Histological examination showed sheets and/or strands composed almost entirely of clear vacuolated epithelial cells in a stroma containing intercellular amyloid-like material and calcification. Histochemical and ultrastructural analysis detected cytoplasmic glycogen granules in the clear cells, and positive immunoreactivities for cytokeratins 8, 13 and 19; filaggrin and anti-ameloblastoma antibodies suggested an odontogenic epithelial origin.

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.

Human cementum tumor cells have different features from human osteoblastic cells in vitro

Cells obtained from human cementoblastoma and alveolar bone were isolated and cultured. Initial and late stages of mineralization were assessed by using atomic force microscopy, scanning electron microscopy and X-ray microanalysis. In cultures of cementoblastoma-derived cells the initial stages of mineralization showed well-defined spherical-shaped structures, while the osteoblastic cells showed plaque-like deposits. These morphological patterns of mineral deposition could serve as nucleation centers for hydroxyapatite crystals. Late stages of mineralization at 28 and 35 d maintained those morphological differences established in initial cultures. The material deposited by cementoblastoma and osteoblastic cells, analyzed by EDX spectra, revealed similar Ca/P ratios for both cell types. These values were similar to those reported for hydroxyapatite in enamel and bone. Alkaline phosphatase specific activity (AlP), of osteoblastic cells at 3, 7 and 11 d, showed an increase of 27.9, 50.9 and 37.0% (p < 0.001), respectively. However, at 15 and 19 d there was an increase of AlP activity of cementoblastoma cells by 39.4 and 34.5% over osteoblastic cells (p < 0.001). Immunostaining of cementoblastoma and osteoblastic cells using a specific mAb against a cementum-derived attachment protein revealed strong immunostaining of cementoblastoma cells which was localized to the cell membrane and fibril-like structures (96.2 +/- 1.3). A few osteoblastic cells also stained weakly with the anti-CAP mAb (6.4 +/- 0.6). Sections of decalcified paraffin embedded cementoblastoma specimens, when immunostained with anti-CAP mAb, showed strong immunostaining of the cells surrounding the regular and irregularly-shaped calcified masses of the tumor. Putative cementocytes also stained positively. Immunostaining with a polyclonal antibody against osteopontin strongly stained the osteoblastic cells (89.0 +/- 3.6). Cementoblastoma cells showed weaker staining (54.2 +/- 2.4). The results suggest that cementoblastoma cells could be a major source of specific cementum proteins. These cells could provide the opportunity to elucidate the regulation of the cementogenesis process.

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.

Odontogenic myxofibroma arising from the periodontal ligament in the maxillary molar region

A rare case of odontogenic myxofibroma, which arose from the periodontal ligament and expanded into the oral cavity resulting in an epulis-like lesion in a 52-year-old man, is reported including details of studies using lectin histochemistry, transmission electron microscopy (TEM), and immunohistochemistry. Most of the tumor cells, which appeared spindle-like with abundant rough endoplasmic reticulum and some microfilaments by TEM, showed immunoreactivity for mesenchymal markers. Some tumor cells, which were polygonal and contained many microfilaments and some filament bundles, were immunoreactive for muscle markers. The present case was considered to consist of many fibroblasts and some myofibroblasts.

[Clear cell odontogenic carcinoma]

Histopathologic and immunohistochemical features of 3 cases of clear cell odontogenic carcinoma were studied. The tumors were composed of sheets or islands of clear cells separated by mature collageneous tissue. Basaloid cells were also seen in the tumors. Tumor cells showed positive reactions for epithelial membrane antigen and cytokeratin. More PCNA positive cells were seen in basaloid cells than in clear cells. Metastasis to regional lymph nodes was found in all 3 cases.

Odontogenic myxoma of the jaws: a clinical, radiologic, immunohistochemical, and ultrastructural study

Ten cases of odontogenic myxoma were evaluated radiologically, histologically, and histochemically. Ultrastructural examination was performed in five cases. Stellate cells with branching processes were seen in an abundant acid mucopolysaccharide background. Occasionally macrophages were found in the tumors. In two cases islands of inactive odontogenic epithelium were identified. The ultrastructural features suggest that many lesional cells are very similar to a myofibroblast. With the avidin-biotin complex immunohistochemical technique, the lesions were tested with antibodies to S- 100 protein, neuron-specific enolase, neurofilaments, glial fibrillary acid protein, keratin, desmin, muscle-specific actin, and vimentin. All the lesions were found to be positive for vimentin and muscle-specific actin, and negative for the rest. The results of our study seem to confirm the muscle-specific actin-positivity of odontogenic myxomas as previously reported.

Calcifying epithelial odontogenic tumours in small domesticated carnivores: histological, immunohistochemical and electron microscopical studies

Histological, immunohistochemical and electron microscopical studies revealed one feline and four canine calcifying epithelial odontogenic tumours in 115 oral tumours over a 10-year period. The tumours consisted of islands and sheets of odontogenic epithelium of varying size within a stroma of fibrous connective tissues. The tumour cells were pleomorphic with variable amounts of eosinophilic cytoplasm and large hyperchromatic, polymorphic nuclei with prominent nucleoli. Clusters of keratinized tumour cells ("shadow cells") were frequently seen within the islands and sheets. The multiple spherules of homogeneous eosinophilic material stained positively with Congo red and Dylon stains and produced an apple green birefringence under polarization microscopy, indicative of amyloid. Mineralized foci were scattered throughout the tumour masses and in the homogeneous spherules. Immunohistochemically, the tumour cells reacted with anti-human keratin antibody, but not with anti-human vimentin or anti-chicken desmin antibodies. The homogeneous spherules did not react with anti-human keratin, anti-human vimentin, anti-chicken desmin, anti-amyloid A, anti-laminin or anti-human collagen (type I, III, IV) antibodies. Ultrastructurally, the cytoplasm of tumour cells was abundant and contained a large number of electron-dense bundles of tonofilaments. The homogeneous spherules consisted of fine filaments measuring about 10-12 nm in diameter.

An immunohistochemical study of two cases of either peripheral odontogenic fibroma (WHO type) or peripheral ameloblastoma

Two cases of either peripheral odontogenic fibroma (POF) (WHO type) or peripheral ameloblastoma are reported. Their immunohistochemical characteristics were investigated in an attempt to clarify their histogenesis. The results showed that the epithelial component of this neoplasm tended to retain its distinct odontogenic character and expressed a keratin profile different from that of the overlying oral epithelium from which both cases most probably originated. The connective tissue element of these tumors was vimentin-positive and S-100 protein negative, confirming their mesodermal nature but precluding the possibility of ectomesenchymal derivation. No reactivity for desmin was noted.

S100, alpha-smooth muscle actin and cytokeratin 19 immunohistochemistry in odontogenic and soft tissue myxomas

AIMS

To compare the expression of S100 protein, alpha-smooth muscle actin (alpha-SMA) and keratin 19 in odontogenic myxomas and non-odontogenic myxoid lesions.

METHODS

Formalin fixed, paraffin wax embedded tissue from seven odontogenic myxomas, three soft tissue myxomas, six hyperplastic myxoid dental follicles, two intramuscular myxomas, 12 cardiac myxomas, and seven normal dental follicles were examined immunocytochemically for S100 protein, alpha-SMA and cytokeratin 19 using the Streptavidin-biotin method.

RESULTS

A minority of odontogenic myxomas (three of seven) were positive for S100 and the staining was of moderate intensity and in all myxofibroblasts. Soft tissue myxomas, normal dental follicles, intramuscular myxomas, and most enlarged myxoid follicles were negative. In the cardiac myxomas the cells forming cords and islands were positive in approximately half (seven of 12), but the dispersed stellate myxoblasts were positive in only two cases. A population of cells in all the odontogenic myxomas and hyperplastic dental follicles contained alpha-SMA, but such cells were sparse in cardiac myxomas and present in only four cases. Cytokeratin 19 was present in odontogenic epithelium of odontogenic myxoma and follicles.

CONCLUSIONS

A minority of odontogenic myxomas, but not other oral myxoid lesions, may express S100 protein and this could cause difficulty distinguishing myxoma from myxoid nerve sheath tumours. Sparse myofibroblastic cells occurred in all types of myxoma tested. The epithelium sometimes found within jaw myxomas expresses cytokeratin 19 and this is consistent with an odontogenic origin.

Expression of tenascin in odontogenic tumours

We investigated the expression of tenascin in a series of odontogenic tumours (n = 63) of epithelial and epithelial-ectomesenchymal origin by using immunohistochemical methods. A heterogeneity of expression of tenascin was observed in odontogenic tumours. The heterogeneity was most prominent in odontogenic tumours not forming calcified tissues. In these ameloblastomas and adenomatoid odontogenic tumours, tenascin was mainly localised at the epithelial tumour cell-mesenchymal tissue interface. In the calcifying epithelial odontogenic tumour, ameloblastic fibroma and odontoma, a widespread stromal immunoreactivity was observed which was, however, unreactive in the calcified masses. The stellate reticulum-like cells and granular cells of ameloblastoma also showed a positive immunoreactivity for tenascin. The results of the present study suggest that expression of tenascin in the stromal tissue of odontogenic tumours differs according to the potential of forming calcified masses by the tumour cells irrespective of tumour cell morphology.

Odontogenic myxoma--characterisation of the extracellular matrix (ECM) of the tumour stroma

In order to elucidate the origin of the odontogenic myxoma, the composition and the structural organisation of the extracellular matrix (ECM) of this tumour were characterised. Collagen type I, VI, procollagen type III, undulin, tenascin and fibronectin were demonstrated in biopsy material of 4 cases by polyclonal antibodies. The tumour stroma showed a pronounced reaction for collagen type I. Fibroblasts displayed an intense intracytoplasmatic reaction for procollagen type III, and collagen type I was not found in the fibroblasts of the adjacent normal oral mucosa. In contrast to the surrounding connective tissue, label for collagen type VI was weak, as was the reaction for fibronectin and tenascin. Undulin was almost undetectable. The immunohistochemical results suggest that the odontogenic myxoma is characterised by an as yet unobserved structural organisation of ECM proteins, a secretion defect of fibrillar collagens type I and III with no resemblance to physiological tooth development.

Immunohistochemical demonstration of tenascin and fibronectin in odontogenic tumours and human fetal tooth germs

The distribution of tenascin and fibronectin (plasma fibronectin) was studied immunohistochemically in ameloblastomas, ameloblastic fibromas and ameloblastic carcinomas, as well as in tooth germs using monoclonal antibodies. Tenascin is an extracellular matrix molecule that was shown to be enriched in the embryonic mesenchyme surrounding the budding epithelium in various organs, including the tooth. Tenascin was strongly expressed in the basement membrane zone of the ameloblastomas and in the early tooth germ and the dental lamina, but not in the dental follicle. The expression of tenascin in the ameloblastic fibroma was seen in the basement membrane of the epithelial islands throughout the stromal tissues. There were clear differences in fibronectin expression in the follicular ameloblastoma and ameloblastic carcinoma. The results suggest that tenascin and fibronectin are involved in epithelial mesenchymal interactions of the tooth germ and in odontogenic tumours.

EGF receptor and its ligands, EGF and TGF-alpha, in developing and neoplastic human odontogenic tissues

Epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-alpha) regulate cell proliferation and functional maturation through the EGF receptor (EGF-R). Their roles in human tooth development and odontogenic tumorigenesis have not been explored. We studied the expression of EGF, TGF-alpha and EGF-R in human fetal teeth (cap stage to early hard tissue formation) and various odontogenic tumors. EGF-R mRNA and immunoreactive cells were mostly located in odontogenic epithelium. EGF-R expression was subject to temporospatial variation at different stages of tooth development. EGF and TGF-alpha mRNAs were detected in fetal teeth only by the reverse transcription polymerase chain reaction (RT-PCR). However, EGF and TGF-alpha immunoreactive cells were demonstrated in epithelial elements of tooth germ, suggesting that the peptides partially originate from non-odontogenic sources. In odontogenic tumors, EGF-R mRNA and immunoreactivity were confined to neoplastic epithelium. Transcripts for TGF-alpha but not for EGF were detected in tumors of odontogenic epithelial, epithelial-ectomesenchymal and ectomesenchymal origins. It is concluded that regulation of EGF-R expression is developmentally regulated in human odontogenesis. Furthermore, the odontogenic epithelium is the main target tissue for both EGF and TGF-alpha during tooth development. TGF-alpha and its receptor may also be involved in odontogenic tumorigenesis.

Unusual granular cell odontogenic tumor. Report of two undescribed cases with features of granular cell ameloblastoma and plexiform granular cell odontogenic tumor

Granular cell ameloblastoma (GCA) is a well recognized variant of follicular ameloblastoma with extensive granular cell change. In contrast, plexiform granular cell odontogenic tumor (PGCOT) is a rare and recently described lesion characterized histologically by a monophasic plexiform pattern of granular cells. In this paper, two cases of an unusual granular cell odontogenic tumor exhibiting combined features of these two entities are described along with their immunohistochemical characteristics. The granular cells of both the GCA and PGCOT areas showed similar patterns of expression for keratin and S-100, which differed from those of typical ameloblastoma. No reactivity for desmin or vimentin was noted. The histomorphologic and immunohistochemical features of these hybrid tumors suggest that the granular cells present have a common origin, most probably the odontogenic epithelium.

Distribution of extracellular matrix proteins in odontogenic tumours and developing teeth

The distribution of two cellular fibronectins (cFn), tenascin, laminin, as well as type VII collagen was studied in 14 benign odontogenic tumours of epithelial (ameloblastoma) and epithelial-ectomesenchymal (ameloblastic fibroma) origins, as well as in developing human teeth by immunocytochemical means using monoclonal antibodies (Mabs). An extradomain sequence-A-containing form of cFn (EDA-cFn) was seen in the extracellular matrix (ECM) of all tumours studied and in the mesenchyme of the developing tooth germs, indicating that cFn in these tissues are predominantly produced locally. A form of cFn containing an oncofetal domain (Onc-cFn), hitherto found only in carcinomas, was detected focally in the stroma of most ameloblastomas but was absent from ameloblastic fibromas and tooth germs. Tenascin was strongly expressed in the basement membrane (BM) zone of all odontogenic tumours and in that of the early tooth germs. Focal absence of laminin and type VII collagen from the BM of some ameloblastomas and the presence of Onc-cFn in the ECM of most ameloblastomas may correlate with their aggressive behaviour. The results also suggest that EDA-cFn and tenascin are involved in epithelial-mesenchymal interactions during tooth development and in odontogenic tumours.

Odontogenic myxoma: histochemical and ultrastructural study

Three cases of odontogenic myxoma are presented, two of which were located in the mandible and one in the maxilla. All cases demonstrated similar morphology by light microscopy. Immunohistochemical studies demonstrated positive reaction with antibodies to vimentin and actin, and negative reaction to antibody to S-100 protein. A 127-day-old human tooth bud was used as a control. The ultrastructural features performed on Case 3, when combined with the immunohistochemical findings suggest that the cells comprising odontogenic myxoma are of myofibroblastic origin.

Epidermal growth factor receptor in odontogenic cysts and tumors

The expression of epidermal growth factor receptor (EGFR) was investigated in 67 cases of odontogenic cysts and 35 cases of odontogenic tumors using monoclonal antibody to EGFR (Biomarker, Israel) to determine the presence and significance of this transmembrane growth factor receptor. The cystic epithelial cells of odontogenic cystic lesions (keratocyst 60%; primordial cyst 75%; radicular cyst 35%; and follicular cyst 47.4%) were positive to EGFR staining. Cytochemical characterization of EGFR in those cystic epithelium was cell membrane positive type as in the normal epithelium. No expression of EGFR was found in the odontogenic tumors. This diversity of EGFR represents no binding activity of EGF, or loss of EGFR in the tumor cell upon EGFR mediated growth in odontogenic tumors was suggested a different tumor cell growth factor status or microenvironment in cell proliferation mechanism at the cellular level in cysts and tumors of odontogenic origin.

Ectomesenchyme of ameloblastic fibroma reveals a characteristic distribution of extracellular matrix proteins

The distribution of collagens type I, IV and VI, procollagen type III and of undulin was studied in four cases of ameloblastic fibroma (AF). The ectomesenchyme of AF revealed an as yet unobserved organization of these extracellular matrix proteins with collagen type VI clearly predominating over collagen type I, procollagen type III and undulin, that showed a weak and amorphous distribution throughout the tumor stroma. Undulin, a glycoprotein that is associated with mature collagen fibrils and with differentiated tissues, was not detectable in the tumor stroma of AF except for a slow expression around capillaries and in areas with a high cellularity. We could demonstrate that the characteristics of extracellular matrix composition allowed a clear distinction between the ectomesenchyme of AF and the adjacent normal mesenchymal stroma. Due to the specific staining patterns it was possible to detect epithelial tumor islands outside the typical ectomesenchymal stroma. Our findings furthermore indicate that epithelial cells of AF invade the adjacent normal mesenchyme possibly inducing de novo formation of ectomesenchymal tumor stroma.

Immunohistochemical evaluation of oral myxoid lesions

Oral examples of neurothekeomas (nerve sheath myxomas), soft tissue myxomas, and focal mucinous and odontogenic myxomas were examined for selected markers. With the use of avidin-biotin complex staining procedures, these specimens of lesions were stained with antibodies to S-100 protein, neurospecific enolase, neurofilaments, desmin, and vimentin. Our results show that the use of immunohistochemical markers for these neural antigens can aid in distinguishing nerve sheath myxomas from other oral myxoid lesions.

Immunohistochemical demonstration of enamel proteins in odontogenic tumors

Immunohistochemical localization of two enamel proteins, amelogenin and enamelin, in comparison with that of keratin, was determined in odontogenic tumors and the allied lesions in order to verify functional differentiation of the tumor cells as ameloblasts. Amelogenin and enamelin were demonstrated in small mineralized foci and in the tumor cells surrounding them in adenomatoid odontogenic tumor (AOT), calcifying epithelial odontogenic tumor (CEOT), and calcifying odontogenic cyst (COC). Hyaline droplets in AOT showed positive staining for both enamel proteins. These mineralized and hyaline materials were not positive for keratin, although tumor cells were positive. On the other hand, no immunoreaction for enamel proteins was obtained in ameloblastoima and odontogenic epithelial cell nests within myxoma and epulis. The results suggest that tumor cells of AOT and CEOT and lining epithelial cells of COC show ameloblastic differentiation in part, but that ameloblastoma cells do not attain functional matauration as secretory phase ameloblasts.