Cytokeratins in epithelia of odontogenic neoplasms

LIM homeobox 8 reduced apoptosis and promoted periodontal tissue regeneration function of dental pulp stem cells

Stem cell-mediated tissue regeneration is a promising strategy for repairing tissue defects and functional reconstruction in periodontitis, a common disease that leads to the loss of alveolar bone and teeth. However, stem cell apoptosis, widely observed during tissue regeneration, impairs its efficiency. Therefore, the regulation of stem cell apoptosis is critical for improving regeneration efficiency. The LIM homeobox 8 gene LHX8, belongs to the LIM homeobox family, which was involved in tooth morphogenesis. Here, we found that LHX8 was significantly expressed in dental pulp. LHX8 knockdown significantly increased dental pulp mesenchymal stem cells (DPSCs) apoptosis, as confirmed by RT-PCR, western blotting, flow cytometry, and transmission electron microscopy. Additionally, LHX8 overexpression inhibited apoptosis and enhanced the osteo/odontogenic differentiation potential of hDPSCs in vitro. Furthermore, LHX8-overexpression could enhance the periodontal tissue regeneration efficiency of hDPSCs in mice with periodontitis. In conclusion, the present study indicates that LHX8 inhibits stem cell apoptosis and promotes functional tissue formation in stem cell-based tissue regeneration engineering, suggesting a new therapeutic target to increase the efficacy of periodontal tissue regeneration.

Adenoid 'ameloblastoma': Clinicopathological description of 4 additional BRAF-negative cases

OBJECTIVE

Adenoid ameloblastoma (AA) is an epithelial odontogenic tumor that was recognized as a separate entity in the last odontogenic classification of WHO in 2022. The etiology is unknown, and the pathogenesis remains controversial. The objective of this study is to contribute the clinicopathological features of 4 additional BRAF-negative cases to the existing literature, aiming to enhance the molecular understanding of this unique tumor in the forthcoming classification.

MATERIALS AND METHODS

This study consists of a case series of four patients diagnosed with AA. The patients' demographic and clinical information were collected from the universities' medical achieves. Histopathologically, all cases were reexamined according to the latest update of the WHO odontogenic tumor classification. In addition to H&E and immunohistochemical stains, cytogenetics was also evaluated.

RESULTS

Well-defined unilocular radiolucent lesions were observed in all cases. Ameloblastoma-like components exhibited reserved nuclear polarity, suprabasal stellate reticulum-like epithelium, duct-like structure, whorls/morules, and cribriform architecture were common features. Variable immunoreactivity to CK7, CK19, CK14, p63, and p40 were determined, and proliferative activity was greater than 15%. The BRAF molecular study revealed no mutations.

CONCLUSIONS

When diagnosing AA, the essential histopathological characteristics must be rigorously applied, and a significant portion of the lesion should contain these features. Additionally, despite limited molecular data, since the BRAF mutation commonly observed in ameloblastomas is not present in the majority of AA cases, we propose changing the term "ameloblastoma" to "ameloblastic" and referring to it as "adenoid ameloblastic tumor" in the forthcoming classification.

Adenoid Ameloblastoma Shares Clinicopathologic, Immunohistochemical, and Molecular Features With Dentinogenic Ghost Cell Tumor: A Comparative Analysis

The updated classification of odontogenic tumors by the World Health Organization (WHO) has included adenoid ameloblastoma (AA) as a distinct entity. However, distinguishing between AA and dentinogenic ghost cell tumor (DGCT) can still be challenging due to their significant morphologic similarities. In this study, we aimed to compare the clinicopathologic, immunohistochemical, and molecular characteristics of AA and DGCT to aid in their differentiation and to shed light on their pathologic mechanisms. Thirteen cases of AA and 14 cases of DGCT (15 samples) were analyzed, along with 11 cases of adenomatoid odontogenic tumor (AOT) and 18 cases of conventional ameloblastoma (AM) for comparative purposes. The study found that AA and DGCT shared a similar long-term prognosis. Immunohistochemically, all cytokeratins detected, except CK8/18, were not statistically significant in differentiating AA and DGCT, while there was a statistically significant difference in the immunophenotype of CK7 and CK10/13 between AA and AM. Nuclear β-catenin accumulation were detected in all cases of AA and DGCT, while AOTs and AMs exhibited cytoplasmic β-catenin. Molecularly, CTNNB1 hotspot mutations were found in only 1 case of AA (1/13), but not found in the other 3 types of tumors. BRAF p.V600E mutation was positive in 2/13 (15%) AA, 1/15 (7%) DGCT, and 2/11 (18%) AOT cases. In comparison, conventional AM was positive for BRAF p.V600E mutation in 94% (17/18) of cases, while KRAS mutations were detected in 63% (7/11) of AOT cases. The study suggests that the so-called AA is a rare benign tumor that exhibits clinical, immunohistochemical, and molecular features similar to DGCTs. Based on these findings, AA should not be categorized as a standalone entity solely based on the presence of whorls/morules and cribriform/duct-like structures. Further studies are needed to investigate the pathologic mechanisms of these tumors and to identify potential therapeutic targets.

Higher immunoexpression of CK14 from the Wnt-1/β-catenin pathway in the development of odontomas

Tooth development depends on a series of reciprocal signaling interactions between the oral epithelium and ectomesenchyme. This study aimed to investigate the role of CK14, a protein involved in Wnt-1/β-catenin signaling, in odontogenesis and the development of odontomas. This cross-sectional, retrospective, immunohistochemical study analyzed 30 compound odontomas, 30 complex odontomas, and 17 tooth germs. Higher immunoexpression of CK14 was observed in odontogenic epithelial cells of tooth germs (p < 0.001) and odontogenic epithelial cells of odontomas (p < 0.001). There was higher immunoexpression of Wnt-1 and β-catenin proteins in epithelial cells of tooth germs (p = 0.002 and p < 0.001, respectively), as well as in the ectomesenchyme of odontomas (p = 0.003 and p < 0.001, respectively). β-Catenin was moderately and significantly correlated with CK14 in the membrane of reduced enamel epithelial cells in odontomas (p = 0.007). Higher immunoexpression of CK14 was observed in the odontogenic epithelium during the bud and cap stages and lower immunoexpression in the internal enamel epithelium during the bell stage. In odontomas, lower expression of Wnt-1/β-catenin and higher immunoexpression of CK14 were found in odontogenic epithelial cells, especially adjacent to the mineralized material resembling the tooth formed in these lesions.

Analysis of the 100 most cited articles on ameloblastoma

OBJECTIVES

An increasing number of articles are published each year. The aim of this is to provide a list of the 100 most cited articles on the subject of ameloblastoma.

METHODS

A bibliographic search was performed on Google Scholar (GS), Microsoft Academic (MA), and Dimensions for ameloblastoma. A ranking was created in order of citation density. Graphical representations of keywords and authorship were created with VOSviewer. Statistical analysis was performed and only results with a 95% confidence interval were considered significant.

RESULTS

A helpful list of top 100 articles was developed to help professionals in a variety of ways. Some curiosities are discussed about this scientometric analysis in ameloblastoma articles.

CONCLUSIONS

A useful list of the top 100 most cited articles on ameloblastoma has been provided. Bibliometric and altmetric analysis using Google Scholar, Microsoft Academic, and Dimensions is a free and excellent tool, not only as a citation manager but also as a study reference.

Maxillary unicystic ameloblastoma: a rare presentation

Unicystic ameloblastoma (UAM), a rare variant of ameloblastoma, is an odontogenic epithelial neoplasm typically appearing in the mandible. We report an extremely rare case of maxillary UAM with an impacted canine and supernumerary tooth. The patient was a woman in her late 30s who presented with a slight expansion of the left anterior maxilla due to a cystic lesion with impacted teeth. Under a clinical diagnosis of dentigerous cyst, the cystic lesion was completely enucleated by extracting the impacted teeth. Based on the clinical features and pathological findings, the final diagnosis was intraluminal UAM in the anterior maxilla. In the present case, despite the rarity of UAM with impacted teeth in the anterior maxilla, it should be considered during differential diagnosis. Careful clinical examination is required for diagnostic accuracy since the clinical findings of tooth-containing ameloblastoma and dentigerous cyst are very similar.

Adenomatoid odontogenic tumor: evidence for a mixed odontogenic tumor

OBJECTIVE

Adenomatoid odontogenic tumor (AOT) was classified by the World Health Organization as a mixed odontogenic tumor in 1992 and reclassified without a clear rationale as an epithelium-only tumor in 2005. The purpose of this study was to investigate if there was any evidence to suggest AOT might be a mixed odontogenic tumor.

STUDY DESIGN

Immunohistochemical studies with nestin, dentin sialophosphoprotein (DSPP), cytokeratin, and vimentin were performed using 21 cases of AOT, and the staining results were analyzed according to the various morphologic patterns seen in AOT. Sirius red stain was used to detect the presence of collagen types I and III in AOT products.

RESULTS

Our results showed that 20 of 21 (95.23%), 0 of 21 (0%), 21 of 21 (100%), and 20 of 21 (95.23%) cases expressed nestin, DSPP, cytokeratin, and vimentin, respectively. Some cells in rosette/duct-like structures (RDSs) expressed nestin, vimentin, or both, without cytokeratin. Coexpression of vimentin and cytokeratin or of nestin, cytokeratin, and vimentin was noted in some cells. Sirius red staining was positive in eosinophilic products in RDSs, double-layered spheres, and dentinoids.

CONCLUSION

Although most AOT cells appear epithelial, there is a small population of cells expressing mesenchymal proteins and secreting collagen types I and III. This evidence suggests that AOT is a mixed odontogenic tumor.

Organoids from human tooth showing epithelial stemness phenotype and differentiation potential

Insight into human tooth epithelial stem cells and their biology is sparse. Tissue-derived organoid models typically replicate the tissue’s epithelial stem cell compartment. Here, we developed a first-in-time epithelial organoid model starting from human tooth. Dental follicle (DF) tissue, isolated from unerupted wisdom teeth, efficiently generated epithelial organoids that were long-term expandable. The organoids displayed a tooth epithelial stemness phenotype similar to the DF’s epithelial cell rests of Malassez (ERM), a compartment containing dental epithelial stem cells. Single-cell transcriptomics reinforced this organoid-ERM congruence, and uncovered novel, mouse-mirroring stem cell features. Exposure of the organoids to epidermal growth factor induced transient proliferation and eventual epithelial-mesenchymal transition, highly mimicking events taking place in the ERM in vivo. Moreover, the ERM stemness organoids were able to unfold an ameloblast differentiation process, further enhanced by transforming growth factor-β (TGFβ) and abrogated by TGFβ receptor inhibition, thereby reproducing TGFβ's known key position in amelogenesis. Interestingly, by creating a mesenchymal-epithelial composite organoid (assembloid) model, we demonstrated that the presence of dental mesenchymal cells (i.e. pulp stem cells) triggered ameloblast differentiation in the epithelial stem cells, thus replicating the known importance of mesenchyme-epithelium interaction in tooth development and amelogenesis. Also here, differentiation was abrogated by TGFβ receptor inhibition. Together, we developed novel organoid models empowering the exploration of human tooth epithelial stem cell biology and function as well as their interplay with dental mesenchyme, all at present only poorly defined in humans. Moreover, the new models may pave the way to future tooth-regenerative perspectives.

Comparative Analysis Between Dentinogenic Ghost Cell Tumor and Ghost Cell Odontogenic Carcinoma: A Systematic Review

Dentinogenic ghost cell tumor (DGCT) and ghost cell odontogenic carcinoma (GCOC) form a spectrum of rare benign and malignant odontogenic neoplasms, respectively. The aim of this study was to perform a comparative systematic review of the clinicopathological, genetic, therapeutic, and prognostic features of DGCT and GCOC. The electronic search was performed until December 2020 on seven electronic databases. Case reports, series, and research studies with enough histopathological criteria for diagnosis and all genomic studies were included. Both DGCT and GCOC showed a male prevalence (p = 0.043), with mandibular and maxillary predilections, respectively (p = 0.008). Peripheral DGCT (DGCTp) affected most elderly people (p < 0.001), and central DGCT (DGCTc) and GCOC occurred mainly in younger individuals. Unilateral enlargement of maxilla or mandible was the most common clinical sign associated with a radiolucent or mixed image. Ameloblastomatous epithelium was often present in both neoplasms. Basaloid and large cells with vesicular nuclei were also frequently seen in GCOC. β-catenin expression and mutations (CTNNB1 gene) were found in DGCT and GCOC. Conservative surgery was mostly used for DGCTp, while radical resection was chosen for DGCTc and GCOC. High recurrence rates were found in DGCTc and GCOC. Metastasis occurred in 16.7% of GCOC cases and the 5-year survival rate was 72.6%. DGCT and GCOC share numerous clinicopathological features and demand a careful histopathological evaluation, considering the overlap features with other odontogenic tumors and the possibility of malignant transformation of DGCT. A strict regular post-operative follow-up is mandatory due to high recurrence rates and metastatic capacity in GCOC.

Odontogenic carcinosarcoma with dentinoid: a rare case report

Odontogenic carcinosarcoma is a very rare malignant odontogenic tumor, characterized by malignant epithelial and mesenchymal components. Studies have reported several cases of odontogenic carcinosarcoma, mainly in the upper and lower jaws, with malignant clinical manifestations. Herein, we present the case of a 58-year-old woman with odontogenic carcinosarcoma with dentinoid in the left maxilla. The invasion range was large, and the left maxillary molar was missing. Histology revealed odontogenic carcinosarcoma with bidirectional differentiation characteristics and comprising three components: malignant epithelium, malignant interstitium, and dentinoid. The patient subsequently underwent nasal endoscopic sinus tumor resection, and she recovered well after surgery. After a strict 4-year follow-up, to date, there are still no signs of disease or local recurrence. To our knowledge, this is the first reported case of odontogenic carcinosarcoma with dentinoid. Our study describes the clinical, morphological, and immunohistochemical characteristics of this case, and distinguishes it from related diseases.

Odontogenic fibroma amyloid-variant: a typical case and brief considerations about mimickers

The World Health Organization's (WHO) updated classification of head and neck tumors (2017) defined odontogenic fibroma as a rare neoplasm. In this report, we describe an unusual, typical and rare variant of a central odontogenic fibroma with diffuse amyloid-like protein stromal deposition, and discuss the differential diagnosis with other entities. Radiographically, this lesion presented as a well-defined radiolucency of the mandible, partially cystic. Histologically, the lesion showed a unique confluence of odontogenic epithelial rests in a moderately cellular connective tissue. Immunohistochemical staining highlighted a mixture of benign epithelial and Langerhans cells within connective tissue with diffuse amyloid-like stromal deposition. The importance of recognizing this variant of odontogenic fibroma is due to its benign prognosis and clinical course.

Sclerosing odontogenic carcinoma - review of all published cases: is it a justifiable addition as a malignancy?

INTRODUCTION

Sclerosing odontogenic carcinoma was a new addition to the list of head and neck tumors by World Health Organization in 2017. This lesion has scarcely been reported and a lack of pathognomonic markers for diagnosis exists.

OBJECTIVE

The aim of the study was to summarize findings from the available literature to provide up-to-date information on sclerosing odontogenic carcinoma and to analyse clinical, radiological, and histopathological features to obtain information for and against as an odontogenic malignancy.

METHODS

We conducted a comprehensive review of literature by searching Pubmed, EBSCO and Web of Science databases, according to PRISMA guidelines. All the cases reported as sclerosing odontogenic carcinoma in English were included. Data retrieved from the articles were gender, age, clinical features, site, relevant medical history, radiographical findings, histopathological findings, immunohistochemical findings, treatments provided and prognosis.

RESULTS

Mean age at diagnosis of sclerosing odontogenic carcinoma was 54.4 years with a very slight female predilection. Sclerosing odontogenic carcinoma was commonly reported in the mandible as an expansile swelling which can be asymptomatic or associated with pain or paraesthesia. They appeared radiolucent with cortical resorption in radiograph evaluation. Histologically, sclerosing odontogenic carcinoma was composed of epithelioid cells in dense, fibrous, or sclerotic stroma with equivocal perineural invasion. Mild cellular atypia and inconspicuous mitotic activity were observed. There is no specific immunohistochemical marker for sclerosing odontogenic carcinoma. AE1/AE3, CK 5/6, CK 14, CK19, p63 and E-cadherin were the widely expressed markers for sclerosing odontogenic carcinoma. Surgical resection was the main treatment provided with no recurrence in most cases. No cases of metastasis were reported.

CONCLUSION

From the literature available, sclerosing odontogenic carcinoma is justifiable as a malignant tumor with no or unknown metastatic potential which can be adequately treated with surgical resection. However, there is insufficient evidence for histological grading or degree of malignancy of this tumor.

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.

Adenomatoid odontogenic tumor mimicking a lateral periodontal cyst - A rare case report in the mandible

Adenomatoid odontogenic tumor (AOT) is benign tumor of the oral cavity characterized by its slow growth accounting to 3%-7% of the odontogenic tumors. AOTs mostly occur in the maxillary anterior region and most often than not associated with impacted anterior teeth. It affects the younger age group, especially below 20 years and is commonly seen in females. It occurs as two main variants - (a) central/intraosseous which is more common and (b) peripheral which is rare. The location of the lesion, its association with the impacted tooth, is the basis for the classification of AOT. The intraosseous type may be related to unerupted tooth (follicular variant) or may not be related to unerupted tooth (extra-follicular variant). Radiologically, AOT presents predominantly as a unilocular cystic lesion enclosing the unerupted tooth. The lesion presents rarely with a cystic component. Radiopacities on the intraoral periapical radiograph are seen as discrete foci having a flocculent pattern within radiolucency even with the presence of minimal calcified deposits. AOT being benign in nature is enucleated with least chances of recurrence. Here, we present a rare case of extra-follicular variant of adenomatoid odontogenic tumor in a 19-year-old female patient.

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.

Adenomatoid Odontogenic Tumor Associated with Impacted Mandibular Canine - A Case Report

Adenomatoid odontogenic tumor (AOT) is a relatively rare, benign, hamartomatous, and cystic odontogenic neoplasm that was first described more than a century ago. It accounts for 2-7% of all odontogenic tumors. The lesion still continues to intrigue experts with its varied histomorphology and controversies regarding its development. The present article describes a case of cystic AOT with an unusual histomorphology associated with an impacted 43 in a 15-year-old male.

An extensive sclerosing odontogenic carcinoma in mandible: a case report and literature review

Sclerosing odontogenic carcinoma (SOC) is a primary intraosseous carcinoma of the jaw that was listed as a separate entity for the first time in the latest version of the World Health Organization classification of Head and Neck Tumors (2017). In this report, we present a case of SOC involving a circuitous diagnostic process because of the inadequately detailed biopsy findings and inherent impression based on the imaging manifestations. Through an extensive literature review, the histopathological and immunohistochemical features of the disease were briefly summarized. Radiological findings of SOC have been characterized in detail, and an imaging classification scheme has been proposed to further discuss the diversity of radiographic features. Due to the rarity of the disease, a comprehensive understanding of SOC is needed, and close collaboration between clinicians, radiologists, and pathologists is crucial to avoid misdiagnosis.

Rare variants of head and neck squamous cell carcinoma -differential immunohistochemical profiles

We aimed to immunohistochemically characterize the pattern of expression of epithelial markers in rare head and neck squamous cell carcinoma (HNSCC) variants: carcinoma cuniculatum (CC) and adenosquamous carcinoma (ASC). We also present an additional variant of HNSCC with concomitant basaloid and squamous components that has overlapping morphological features with odontogenic and non-odontogenic tumors, which we termed basalo-squamous carcinoma (BSC). The selected markers included CK5/6, p40, CK19, BerEP4, p16 and SOX10. All tumors were CK5/6 and p40 positive. CK19 and BerEP4 were positive in BSC and focally in ASC but negative in CC. p16 was positive in 3 (60%) of the CCs, focally positive in ASC and negative in BSC. SOX10 was negative in all three variants. Our results highlight the plasticity of the lining epithelium revealing differential profiles of immuno-expression of the selected molecular markers, possibly reflecting their diverse histopathogenesis.

Primordial odontogenic tumor: a case report and literature review

Background

A primordial odontogenic tumor (POT) is a rare, benign, mixed epithelial and mesenchymal odontogenic tumor that has been included as a new entity in the latest World Health Organization (WHO) classification (2017). POT consists of dental papilla-like myxoid connective tissue covered with a delicate membrane of ameloblastic epithelium. Only 15 cases have been documented worldwide, and here, we report the sixteenth case and the first one of South Korea.

Case presentation

An asymptomatic lesion was discovered as an incidental radiographic finding in a 10-year-old boy. The patient had no complaints about the lesion. Cone-beam computerized tomograms revealed a round cavity with a defined cortical border measuring approximately 5 × 5 × 5 mm in size. The lesion was a POT. The patient was treated with enucleation. The tumor showed no recurrence for one year.

Conclusion

This is the first report of POT in South Korea using the novel diagnosis of POT after it was recognized and defined in the latest WHO classification. This novel diagnosis will be useful for pathologists and clinicians in diagnosing and differentiating this new and rare disease from other odontogenic tumors.

Role of Cytokeratin-7 in the pathogenesis of odontogenic cysts - an immunohistochemical study

Introduction

Odontogenic cysts are distinct entities and quite a common occurrence in the jaw bones. These are individual lesions which arise from the same odontogenic apparatus but with varying pathogenesis. Cytokeratins are integral components in tooth development and are expressed across the odontogenic tissues in physiological and pathological states.

Aim

To elucidate the role of cytokeratin-7 in the pathogenesis of odontogenic cysts by immunohistochemistry.

Method

Cytokeratin-7 (CK-7) was assessed in 39 cases of odontogenic lesions retrieved from the archival files which included 15 cases of dentigerous cysts (DC), 12 cases of odontogenic keratocysts (OKC) and 12 cases of radicular cysts (RC) and also 8 cases of control specimens.

Statistical analysis

Results obtained were statistically analyzed using chi-square test to assess the association between different odontogenic cysts used in this study and Cytokeration-7 staining. The difference was considered to be of statistical significance if the p value was ≤ 0.05.

Results

CK7 expression was maximum in dentigerous cycts (66.66%) followed by radicular cysts (41.66%) and odontogenic keratocysts (16.6%). On evaluation of staining and expression pattern, highest positivity is shown in dentigerous cysts and the positivity is seen in suprabasal (60%) and superficial layers (40%) whereas radicular cysts and odontogenic keratocysts showed positivity in superficial and spinous layers.

Conclusion

Cytokeratin-7 expression correlates with the degree of differentiation of the epithelium. So the cysts with a well-differentiated epithelium (RC and DC) express CK-7, while the cysts with a less well-differentiated epithelium (OKC) show slight positivity. Thus it can be useful to differentiate OKC from DC and RC.

Ameloblastic Fibroma of the Mandible Reconstructed with Autogenous Parietal Bone: Report of a Case and Literature Review

Ameloblastic fibroma (AF) is a rare, slow-growing benign neoplasm, comprised of tissues of odontogenic origin. It constitutes 2% of odontogenic tumours, occurring at any age, but has a predilection to present in the first two decades of life. AF principally affects the posterior mandible. It is characterized by epithelial islands and cords immersed in ectomesenchyme that mimics the dental papilla and enamel organ but without actual hard tissue formation. Herein, we describe the case of a 6-year-old Caucasian male who presented to the Oral and Maxillofacial Department at Alder Hey Children's Hospital, Liverpool, UK, with a painless expansile mass in the left mandible which was diagnosed as a benign ameloblastic fibroma and subsequently enucleated and reconstructed with a parietal calvarial bone graft. A brief literature review and the issues surrounding diagnosis are discussed.

Cytokeratin and fibronectin expression in orthokeratinized odontogenic cyst: A comparative immunohistochemical study

Background

The orthokeratinized odontogenic cyst (OOC) is a rare developmental jaw cyst. It is crucial to distinguish it from keratocystic odontogenic tumor (KCOT) in all parameters including clinical behavior, immunohistochemical (IHC) profile and prognosis. This study aimed to analyze the IHC expression of cytokeratins and fibronectin in OOC, epidermoid cyst and dermoid cyst (EDC/DMC), dentigerous cyst (DC) and KCOT in order to explicate the pathogenesis of OOC.

Materials and Methods

Twenty-five cases of all study groups were incubated with CK10, CK13, CK19 and fibronectin antibodies and staining was assessed in the basal, intermediate and surface layers of epithelium. All the data were analyzed by SPSS software. Nonparametric Chi-square test and Spearman's correlation test were applied.

Results

The overall expression pattern of CK10, CK13 and CK19 was similar and resembled each other in the study groups of OOC and EDC. The immunoexpression was almost akin to each other in DC and KCOT.

Conclusion

It was inferred from the results that the IHC profile of OOC is different from DC and KCOT and closer to EDC.

Evaluation of cytokeratin 19 as a prognostic tumoral and metastatic marker with focus on improved detection methods

In the last few years, there has been a growing interest in Cytokeratin 19 (CK19) studies in the cancer research field. CK19 belongs to the Type I CKs, serves as a useful research tool in prognosis, diagnosis, and management of the tumors. In this paper, we dissect the metastatic potential of CK19, its relation with cancer stem cells and retinal epithelial cells behavior, its application as a tumor marker and its role among 30 cancers such as thyroid, thoracic, lung, pancreatic, cervical, colorectal, and so forth. CK19 expressed in several cancer types because of its metastatic potential. This paper also presents modified detection methods of CK19 in disseminated tumor cells.

The Challenging Diagnosis of Primordial Odontogenic Tumor

Primordial odontogenic tumor (POT) is a benign mixed odontogenic tumor comprised of a loose connective tissue with a similar morphology with dental papilla and exhibiting in its periphery the presence of a columnar epithelium. POT occurs in young patients and typically is associated with an unerupted tooth, with the mandible being the main anatomic site of occurrence. The present manuscript is aimed at describing a new case of POT and reviewing the main biologic findings related to this odontogenic tumor.

Benign odontogenic ghost cell lesions revisited and new considerations on dysplastic dentin

OBJECTIVES

This study aimed to revisit benign odontogenic ghost cell lesions (BOGCL) by hematoxylin and eosin staining and immunohistochemistry.

MATERIALS AND METHODS

Thirty cases of calcifying odontogenic cyst (COC) and 6 cases of dentinogenic ghost cell tumor (DGCT) were selected for histopathological and immunohistochemical analysis. Sections stained for cytokeratin (K) 14, K-19, amelogenin, collagen type 1 (COL-1), and dentin matrix acidic phosphoprotein 1 (DMP-1) were evaluated using qualitative analysis. Sections stained for Ki-67 and minichromosome maintenance protein-2 (MCM-2) were evaluated using semi-quantitative analysis.

RESULTS

A morphologic overlap was noticed in all BOGCL. Moreover, no differences were detected in the expression of K-14 and K-19. The expression of proliferative markers Ki-67 and MCM-2 was similar between cystic and tumor lesions (p > .05). The presence of COL-1 and absence of amelogenin in the so-called dysplastic dentin, associated with its histologic pattern, suggest that this is in fact an enameloid-like tissue.

CONCLUSIONS

The dysplastic dentin should be considered an enameloid-like tissue in these lesions.

CLINICAL RELEVANCE

The similarity in histology, protein expression, and proliferative marker indices between COC and DGCT suggest that they are a sole entity and likely represent types of the same neoplasia.

Ameloblastoma with adenoid features: A series of eight cases

BACKGROUND

Ameloblastoma with adenoid features are characterized by the presence of duct-like structures formed from the parenchyma of the tumor. This study was conducted to report a series of eight ameloblastomas with adenoid features, highlighting their clinicopathological and immunohistochemical aspects.

MATERIAL AND METHODS

Out of 71 cases of ameloblastomas, this study classified 8 cases as ameloblastomas with adenoid features. Clinicopathological data and immunohistochemistry for CK7, CK14, CK19, IMP3, p53 and Ki-67 were evaluated.

RESULTS

From those cases of ameloblastoma exhibiting adenoid features, there were 4 women and 4 men, with mean age of 39 years. Most cases affected the mandible and all presented radiographically as a radiolucency. The predominant histopathological features were pseudoducts, squamous metaplasia, nuclear hyperchromatism, clear cells, whorled aspect of epithelial structures, cribriform growth pattern, proliferation of spindle cells and extracellular eosinophilic material. Immunohistochemical analysis showed high expression for CK14 (n = 6) and CK19 (n = 3) and all cases (n = 8) were negative for p53, IMP3 and CK7. In addition, all samples (n = 8) showed low expression for Ki-67.

CONCLUSIONS

The similarities between the histopathological and immunohistochemical features of eight cases described in the present study and those described in previous studies support the possibility that these lesions are adenoid ameloblastomas. In addition, the immunohistochemical results of CK14, CK19, p53 and Ki-67 did not differ from those of conventional ameloblastomas.

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.

Comparative histological and immunohistochemical study of ameloblastomas and ameloblastic carcinomas

BACKGROUND

This study aimed to compare the histological and immunohistochemical characteristics of ameloblastomas (AM) and ameloblastic carcinomas (AC).

MATERIAL AND METHODS

Fifteen cases of AM and 9 AC were submitted to hematoxilin and eosin (H&E) and immunohistochemical analysis with the following antibodies: cytokeratins 5,7,8,14 and 19, Ki-67, p53, p63 and the cellular adhesion molecules CD138 (Syndecan-1), E-cadherin and β-catenin. The mean score of the expression of Ki-67 and p53 labelling index (LIs) were compared between the groups using the t test. A value of p<0.05 was considered to be statistically significant.

RESULTS

All cases were positive for CKs 5, 14 and 19, but negative for CKs 7 and 8. CKs 5 and 19 were positive mainly in the central regions of the ameloblastic islands, while the expression in AC was variable in intensity and localization. CK14 was also variably expressed in both AM and AC. Ki-67 (P=.001) and p53 (P=.004) immunoexpression was higher in AC. All cases were positive for p63, but values were higher in AC. CD138 was mainly expressed in peripheral cells of AM, with a weak positivity in the central areas, while it was positive in most areas of ACs, except in less differentiated regions, where expression was decreased or lost. E-cadherin and β-catenin were weakly positive in both AM and AC.

CONCLUSIONS

These results shows that Ki-67, p53 and p63 expression was higher in AC as compared to AM, suggesting that these markers can be useful when considering diagnosis of malignancy, and perhaps could play a role in malignant transformation of AM. Pattern of expression of CKs 5 and 19 in AC were different to those found in AM, suggesting genetic alterations of these proteins in malignant cells. It was confirmed that CK19 is a good marker for benign odontogenic tumors, such as AM, but it is variably expressed in malignant cases.

Comparative study of cytokeratin and langerin expression in keratinized cystic lesions of the oral and maxillofacial regions

Dermoid cysts (DMCs) and epidermoid cysts (EDMCs) usually arise in soft tissues, whereas orthokeratinized odontogenic cysts (OOCs) and keratocystic odontogenic tumors (KCOTs) develop in the jaw. In this study, we performed immunohistochemical analysis of cytokeratins (CKs) to examine differences in the lining epithelium of DMCs, EDMCs, OOCs, and KCOTs. In addition, we carried out immunohistochemical examination of langerin to clarify the biological characteristics of the orthokeratinized lining epithelium of DMCs, EDMCs, and OOCs. Seven DMCs, 30 EDMCs, 11 OOCs, and 28 KCOTs were examined immunohistochemically using antibodies against CK10, 13, 14, 16, 17, 19, and langerin. Immunoreactivities for CKs and langerin in oral DMCs and EDMCs were similar to those of lesions affecting the skin. Positive reactivity for CK13 and 17 was evident in OOCs, but not in DMCs/EDMCs. CK10 was significantly positive in all layers except for the basal layer in OOCs, but was negative in KCOTs. CK17 was positive in all layers in KCOTs, and in all layers except for the basal layer in both OOCs and dentigerous cysts. CK19 was negative in OOCs. Langerhans cells were found mainly in OOCs, but were hardly evident in KCOTs. These results suggest that DMCs/EDMCs, OOCs and KCOTs are independent diseases.

Twist and Snail expression in tumor and stromal cells of epithelial odontogenic tumors

BACKGROUND

The aims of this study were to evaluate expression of Twist and Snail in tumor and stromal cells of epithelial odontogenic tumors and to analyze relationships between Twist and Snail expression and between tumor and stromal expression.

METHODS

Immunohistochemistry was performed using Twist and Snail antibodies in 60 ameloblastomas (AMs; 20 solid/multicystic, 20 unicystic, and 20 recurrent), six ameloblastic carcinomas (ACs), 10 adenomatoid odontogenic tumors (AOTs), and six calcifying epithelial odontogenic tumors (CEOTs).

RESULTS

A higher rate of tumor cells strongly positive for Twist was observed in AC compared to the other tumors (P = 0.019). The rate of tumor cells strongly positive for Snail tended to be higher in AC than in AM (P = 0.060). AM and AC showed a higher rate of Twist-positive stromal cells than AOT and CEOT (P < 0.001). Tumor cells of recurrent AM showed stronger expression of Twist (P < 0.001) and Snail (P = 0.001) compared to AM without recurrence. A moderate positive correlation was observed between tumor expression of Twist and Snail (r = 0.376, P = 0.001) and between tumor and stromal expression of Snail (r = 0.334, P = 0.002).

CONCLUSIONS

Twist and Snail may affect the epithelial-mesenchymal transition in AC and be involved in recurrence of AM. Stromal Twist expression may be associated with aggressive clinical behavior of epithelial odontogenic tumors. A Twist-Snail pathway may participate in the development and progression of odontogenic tumors, and tumor-stroma interaction in odontogenic tumors may be mediated by Snail.

Murine matrix metalloproteinase-20 overexpression stimulates cell invasion into the enamel layer via enhanced Wnt signaling

Matrix metalloproteinase-20 (MMP20) is expressed by ameloblasts in developing teeth and MMP20 mutations cause enamel malformation. We established a stably transfected Tet-Off Mmp20-inducible ameloblast-lineage cell line and found that MMP20 expression promoted cell invasion. Previously, we engineered transgenic mice (Tg) that drive Mmp20 expression and showed that Mmp20(+/+)Tg mice had soft enamel. Here we asked if Mmp20 overexpression disrupts ameloblast function. Incisors from Mmp20(+/+) mice expressing the Mmp20 Tg had a striking cell infiltrate which nearly replaced the entire enamel layer. A thin layer of enamel-like material remained over the dentin and at the outer tooth surface, but between these regions were invading fibroblasts and epithelial cells that surrounded ectopic bone-like calcifications. Mmp20(+/+)Tg mice had decreased enamel organ cadherin levels compared to the Mmp20 ablated and WT mice and, instead of predominantly locating adjacent to the ameloblast cell membrane, β-catenin was predominantly present within the nuclei of invading cells. Our data suggest that increased cadherin cleavage by transgenic MMP20 in the WT background releases excess β-catenin, which translocates to ameloblast nuclei to promote cell migration/invasion. Therefore, we conclude that MMP20 plays a role in normal ameloblast migration through tightly controlled Wnt signaling and that MMP20 overexpression disrupts this process.

Peripheral Clear Cell Variant of Calcifying Epithelial Odontogenic Tumor: Case Report and Review of the Literature

Calcifying epithelial odontogenic tumor (CEOT) is classified as an uncommon, benign, odontogenic neoplasm that is exclusively epithelial in origin. Of all reported cases, peripheral tumors account for 5-6 %, among which clear cell variants are still rare. A rare case of peripheral clear cell variant of CEOT occurring in the mandibular gingiva of a 47-year-old female is presented.

Follicular Adenomatoid Odontogenic Tumor in Mandible: A Rare Case Report

Adenomatoid odontogenic tumor (AOT) is a relatively rare, benign, hamartomatous, and cystic odontogenic neoplasm that was first described more than a century ago. The lesion still continues to intrigue experts with its varied histomorphology and controversies regarding its development. The present article describes a case of cystic AOT with an unusual histomorphology associated with an impacted 44 in a 21-year-old male.

Expression of CK14 and vimentin in adenomatoid odontogenic tumor and dentigerous cyst

Background:

Origin of adenomatoid odontogenic tumor (AOT) has long been a controversy, and the issue of it being a neoplasm or hamartoma was a subject of debate for a long time. Earlier it was grouped under a mixed group of odontogenic tumors considering the varying degrees of inductive changes. Recently, the WHO classification states that the presence of hard tissue within AOT was not due to induction but was rather a metaplastically produced mineralization and hence the tumor was reclassified under a group of tumors arising from odontogenic epithelium. This study is an attempt to identify if both epithelial (cytokeratin 14 [CK14]) and mesenchymal (vimentin) markers are expressed in the follicular and extrafollicular variants of AOT and to compare the expression with dentigerous cyst (DC) as this cyst is known to arise from reduced enamel epithelium which expressed CK14. This is done to possibly relate the origin of AOT with reduced enamel epithelium.

Aims and Objectives:

To study, analyze and correlate the expression of CK14 and vimentin in AOT and DC.

Materials and Methods:

Retrospective study on paraffin embedded tissues. Sixteen cases of AOT and 15 cases of DC were retrieved from the departmental archives and subjected to CK14 and vimentin immunostaining.

Statistical Methods:

Measures of central tendency was used to analyze the results.

Results and Observations:

Ninety percent of cases of follicular AOT (FAOT) and 100% cases of extra-follicular AOTs (EAOTs) showed positivity for CK14 and all cases of DC showed positivity for CK14. Vimentin was positive in 44% and negative in 56% cases of both FAOT and EAOT taken together.

Conclusion:

The CK14 expression profile in AOT and DC supports its odontogenic epithelial specific nature. The possible role of reduced enamel epithelium and dental lamina in histogenesis of AOT and DC is strongly evident by their CK14 expression pattern.

Adenomatoid odontogenic tumor associated with an unerupted mandibular lateral incisor: a case report

Adenomatoid odontogenic tumor (AOT) is a rare, benign odontogenic tumor that predominantly appears in the second decade of life in female patients. Most AOTs occur in the anterior part of the maxilla and are usually associated with impacted anterior teeth. There are three types of AOT, follicular, extrafollicular, and peripheral, which are classified based on the location of the lesion and its association with the impacted tooth. We report a rare case of AOT associated with an impacted right mandibular lateral incisor in an 11-year-old female patient.

Cystic Adenomatoid Odontogenic Tumor

Adenomatoid Odontogenic Tumor (AOT) is a well-established benign epithelial lesion of odontogenic origin. Rightfully called "the master of disguise," this lesion has been known for its varied clinical and histoarchitectural patterns. Not only does AOT predominantly present radiologically as a unilocular cystic lesion enclosing the unerupted tooth (which is commonly mistaken as a dentigerous cyst) but the lesion also presents rarely with a cystic component histopathologically. We present one such unusual case of cystic AOT associated with an impacted canine, mimicking a dentigerous cyst. The present case aims to highlight the difference between cystic AOT and dentigerous cyst radiographically. The exact histogenesis of AOT and its variants still remains obscure. An attempt has been made to hypothesize the new school of thought regarding the origin of AOT.

A Peripheral Dentinogenic Ghost Cell Tumor With Immunohistochemical Investigations and a Literature Review-Based Clinicopathological Comparison Between Peripheral and Central Variants

The aim of the study was to present a peripheral dentinogenic ghost cell tumor (DGCT) and to describe clinicopathological differences between peripheral and central variants of the tumor using a selected literature review. The case report is based on a swelling present on the alveolar ridge of a 74-year-old edentulous denture wearer. The lesion was diagnosed as a peripheral DGCT after excluding the presence of a central lesion. Immunohistochemical investigations revealed similar cytokeratin expression pattern, with CK14 and MNF116 positivity in both the tumor and the surrounding surface epithelium. However, in contrast, CK19 expression was restricted to less than 5% of the tumor cells. A clinicopathological comparison was compiled using 30 cases of peripheral DGCTs (including the present lesion) and 16 cases of central DGCTs published over a period of 40 years. Accordingly, peripheral lesions were more often found in elderly denture wearers, in relation to mandibular gingiva and alveolar mucosa. None of the lesions had recurred after excision. In contrast, majority of the central lesions were common in younger individuals and showed a striking male predilection. It occurred equally on both jaws, while approximately 50% of the lesions gave rise to recurrences. In conclusion, similar cytokeratin expression in both the tumor and surface epithelium can be used to support oral surface epithelial origin, while CK14 positivity confirms the odontogenic derivation of the peripheral DGCT described in the report. In contrast to central DGCT, the peripheral DGCT is a distinct lesion with characteristic clinicopathological profile and nonaggressive behavior.

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.

Expression of cytokeratins in enamel organ, junctional epithelium and epithelial cell rests of Malassez

BACKGROUND AND OBJECTIVE

After tooth formation is complete, it is suggested that continuity exists between the epithelial cell rests of Malassez (ERM), reduced enamel epithelium (REE) and subsequently the junctional epithelium. However, the junctional epithelium was reported to differ from REE and ERM. The developmental relationships between and among them remain controversial. Therefore, in the present study we examined the expression of cytokeratins in the three types of epithelia to investigate the epithelial phenotypes.

MATERIAL AND METHODS

The maxillae of Wistar rats, 1, 2, 3 and 7 wk of age, were used, and the expression of CK14, CK17, CK19, CK10/CK13 and AE1/AE3 was detected using immunoperoxidase techniques.

RESULTS

There was negative staining for CK10/CK13 in all the epithelia. ERM stained strongly for AE1/AE3, CK14, CK17 and CK19. During the transformation of inner enamel epithelial (IEE) cells into reduced ameloblasts and subsequently into junctional epithelium, strong staining for CK14 was evident in IEE, REE and junctional epithelium, whereas the expression of AE1/AE3 and of CK19 were initially negative in IEE and then strong in REE and junctional epithelium, respectively. In particular, the expression of CK17 was strongly positive in ERM and REE, but was negative in IEE and junctional epithelium.

CONCLUSION

ERM are of odontogenic origin and junctional epithelium has an epithelial phenotype different from REE and ERM. This is the first report to demonstrate that CK17 can be used as a marker to distinguish junctional epithelium from ERM.

Ossifying odontogenic fibroma: A rare case report

Odontogenic fibroma (OF) is a rare benign odontogenic neoplasm that is most commonly found in the mandibular/premolar region of female patients in the second to fourth decades of life. Well-defined radiolucent lesions that may induce root resorption are normally observed. Rare variants of OF have been described in the prior literature, including references to: 1) giant cell lesions, 2) amyloid-like protein deposition, and 3) ossifying variants. Immunohistochemistry can contribute to understanding the biological behavior and the pathogenesis of OF. Therefore, this case report aimed to describe a new case of ossifying OF and discuss the histopathology and immunohistochemical features.

Key words:Odontogenic fibroma, jaw tumors, ossifying variant.

The diagnostic usefulness of immunohistochemistry for odontogenic lesions

The diagnosis of odontogenic tumors can be challenging, largely due to their rarity and consequent difficulties in gaining experience in their assessment. In most cases, careful attention to morphology, in conjunction with clinical and radiological features will allow a diagnosis to be made. However, in some cases, immunohistochemical analysis of the tumor may be useful. In this review we will outline the immunohistochemical expression profile of normal developing odontogenic tissues and a range of odontogenic tumors. In many cases the immunohistochemical markers are neither specific nor sensitive enough to be of help in diagnosis, but in some cases such analysis may prove very useful. Thus we have outlined a limited number of circumstances where immunohistochemistry may be of use to the practicing diagnostic pathologist.

Odontomas and supernumerary teeth: is there a common origin?

The aim of the present work is to analyze all scientific evidence to verify whether similarities supporting a unified explanation for odontomas and supernumerary teeth exist. A literature search was first conducted for epidemiologic studies indexed by PubMed, to verify their worldwide incidence. The analysis of the literature data shows some interesting similarities between odontomas and supernumerary teeth concerning their topographic distribution and pathologic manifestations. There is also some indication of common genetic and immuno-histochemical factors. Although from a nosological point of view, odontomas and supernumeraries are classified as distinct entities, they seem to be the expression of the same pathologic process, either malformative or hamartomatous.

Primordial odontogenic tumour: clinicopathological analysis of six cases of a previously undescribed entity

AIM

To describe the clinicopathological and immuno-histochemical features of six tumours that do not fulfil the criteria of any of the currently classified odontogenic tumours.

METHODS AND RESULTS

The patients were three males and three females, whose ages ranged from 3 years to 18 years (mean, 11.05 years). In all cases there were well-defined radiolucencies associated with unerupted teeth apparently showing a pericoronal relationship. Microscopically, all tumours were composed of variably cellular loose fibrous tissue with areas similar to dental papilla, entirely surrounded by cuboidal to columnar epithelium resembling the internal epithelium of the enamel organ. Mesenchymal tissue was positive only for vimentin, and Ki67 expression was very low (<2%). The epithelium was positive for CK AE1/AE3, CK5, CK14, and CK19, but negative for CK18 and CK20. All cases showed clear demarcation from the surrounding bone, and were surgically removed, with no recurrences after follow-up ranging from 6 months to 20 years.

CONCLUSIONS

These findings differ from those observed in other odontogenic lesions, such as ameloblastic fibroma, odontogenic myxoma, odontogenic fibroma, and hyperplastic dental follicles. The term primordial odontogenic tumour is proposed to describe this novel lesion.

EGFR signaling downstream of EGF regulates migration, invasion, and MMP secretion of immortalized cells derived from human ameloblastoma

Ameloblastoma is an odontogenic tumor characterized by local invasiveness and frequent recurrence. The surrounding stroma, composed of different cell types and extracellular matrix (ECM), may influence ameloblastoma invasive behavior. Furthermore, tumor and stromal cells secrete matrix metalloproteases (MMPs), which, in turn, can modulate the matrix and promote the release of ECM-bound growth factors. Among these growth factors, epidermal growth factor (EGF) and its receptor, EGFR, have already been shown to stimulate MMP synthesis, suggesting that an interdependent mechanism, involving MMP activity and growth factors release, may contribute to tumor invasiveness. The aim of this study was to evaluate the effects of the EGF/EGFR signaling pathway on migration, invasion, and MMP activity, in a primary cell line derived from human ameloblastoma. We established and characterized a primary cell line (AME-1) from a human ameloblastoma sample. This cell line was transduced with human papillomavirus type 16 (HPV16) E6/E7 oncogenes, generating the AME-HPV continuous cell line. EGF, MMP2, and MMP9 expression in ameloblastoma biopsies and in the AME-HPV cell line was analyzed by immunohistochemistry and immunofluorescence, respectively. Migratory activity of EGF-treated AME-HPV cells was investigated using monolayer wound assays and Transwell chambers. EGF-induced invasion was assessed in Boyden chambers coated with Matrigel. Conditioned medium from EGF-treated cells was subjected to zymography. EGFR expression in AME-HPV cells was silenced by small interfering RNA (siRNA), to verify the relationship between this receptor and MMP secretion. Ameloblastoma samples and AME-HPV cells expressed EGF, EGFR, MMP2, and MMP9. AME-HPV cells treated with EGF showed increased rates of migration and invasion, as well as enhanced MMP2 and MMP9 activity. EGFR knockdown decreased MMP2 and MMP9 levels in AME-HPV cells. EGFR signaling downstream of EGF probably regulates migration, invasion, and MMP secretion of ameloblastoma-derived cells.

Malignant transformation of an odontogenic cyst in a period of 10 years

Primary intraosseous carcinoma of the jaws (PIOSCC) might arise from odontogenic epithelium, more commonly from a previous odontogenic cyst. The aim of this case is to illustrate that the clinician should consider that an apparent benign dentigerous cyst can suffer malignant transformation and that all material removed from a patient must be evaluated histologically. A 44-year-old man presented in a routine periapical X-ray an impacted lower left third molar with radiolucency over its crown. Ten years later, the patient complained of pain in the same region and the tooth was extracted. After one month, the patient still complained of pain and suffered a fracture of the mandible. A biopsy was performed and carcinoma was diagnosed. The patient was treated surgically with adjuvant radio- and chemotherapy and after 8 years, he is well without signs of recurrences. This report describes a central mandibular carcinoma probably developed from a previous dentigerous cyst.