Alteration of primary cilia morphology and associated signalling in ameloblastoma.

OBJECTIVES: Primary cilium is a cellular organelle with growing significance confirmed in tumour biology. Primary cilia have been associated with fine tuning of numerous cell signalling pathways and the role of this structure in cancer initiation and progression is recently at the forefront of attention. Here, we investigated possible alterations in the occurrence of primary cilia and changes of associated signalling in ameloblastoma, which represents the most common odontogenic tumour. METHODS: We performed immunohistochemistry to assess the number and morphology of primary cilia in ameloblastoma tissues. The gene expression of key SHH pathway members was analysed by qPCR. As a functional experiment, we treated a primary ameloblastoma cell line by a SHH pathway inhibitor Sonidegib (LDE225). RESULTS: We uncovered differences in primary cilia distribution and appearance in histological subtypes of ameloblastoma with the highest number of ciliated cells in plexiform and follicular subtypes. SHH protein was located close to primary cilia in ameloblastoma epithelial cells and the expression of molecules downstream of SHH signalling was upregulated. Moreover, the inhibition of SHH pathway by Sonidegib caused downregulation of SHH effector gene GLI1 and cell cycle regulator CCND1 in ameloblastoma primary cell line. The inhibition of SHH signalling also altered the expression of molecules involved in intraflagellar transport. CONCLUSIONS: In conclusion, our study uncovered alterations in number of ciliated cells and associated signalling in ameloblastoma, which indicate SHH inhibitors as potential therapeutic target to treat this disease.

Expression of BMP4 and FOXN1 in orthokeratinized odontogenic cyst compared to odontogenic keratocyst suggests an epidermal phenotype.

Odontogenic keratocysts (OKC) and orthokeratinized odontogenic cysts (OOC) are odontogenic cysts that share histological and immunohistochemical similarity with epidermal appendages and cutaneous cystic lesions despite exhibiting contrasting biological behavior. In epidermal appendages, BMP4 induces expression of FOXN1, which participates in terminal differentiation of keratinocytes and control of proliferation. We compared BMP4 and FOXN1 expression in OOC and OKC to investigate their role in the epithelial differentiation of these cysts. BMP4 and FOXN1 expression was assessed using immunohistochemistry in 20 primary sporadic OKC and compared to 16 OOC. BMP4 epithelial expression was detected in 81.25% OOC compared to 35% in OKC, while its expression in connective tissue was observed in 65% OKC and 75% OOC. FOXN1 was detected in 75% OOC vs. 30% OKC. The "triple positive" phenotype, i.e., BMP4 epithelial and connective tissue positivity and FOXN1 epithelial positivity, was seen in 56.25% OOC compared to 10% OKC. The greater expression of BMP4 and FOXN1 in OOC suggests greater activation of this pathway in OOC, which suggests a role in its more mature epithelium; it also resembles an epidermal phenotype.

Ghost cells unveiled: A comprehensive review.

BACKGROUND: Ghost cells (GCs) are cells with distinct intracytoplasmic keratinization, which leads to the preservation of the cellular outline with a clear area corresponding to the previous nucleus location. GCs may show various patterns, such as degeneration, tissue granulation, and calcification. Their true nature and the mechanism regulating the conversion of odontogenic epithelial cells into GCs remain unclear. GC keratinization is different from normal keratinization as they are larger than keratotic squames, are frequently vacuolated, and have prominent nuclear membrane remnants. Few cystic lesions, odontogenic tumors, and non-odontogenic tumors, such as calcifying odontogenic cyst, craniopharyngioma, pilomatrixoma, odontoma, dentinogenic ghost cell tumor, and ghost cell odontogenic carcinoma, exhibit GCs as a typical feature. The Wnt and Notch signaling pathways play a role in the histogenesis of the neoplasms. HIGHLIGHT: The review clarifies the various proposed hypotheses of the histogenesis of GCs, including molecular pathogenesis. Diagnostic workup for the identification of GCs, including special staining and immunohistochemistry, has been extensively discussed. A stepwise algorithm for identifying odontogenic and non-odontogenic lesions containing GCs has been proposed. Additionally, the prognostic role of GCs in the lesions has been elucidated. CONCLUSION: Among the various hypotheses of the origin of GCs, we suggest that aberrant keratinization is the most accepted based on various immunohistochemical studies and special staining characteristics. GCs are a distinct characteristic entity of many odontogenic and non-odontogenic lesions; however, it remains controversial whether their presence has any pathognomonic role in the biological nature of these lesions.

A comparative immunohistochemical analysis of cortactin in orthokeratinized odontogenic cyst (OOC), sporadic odontogenic keratocyst (OKC), and syndromic OKC.

OBJECTIVES: To evaluate and compare the immunohistochemical expression of cortactin in the epithelial lining of orthokeratinized odontogenic cyst (OOC), sporadic odontogenic keratocyst (OKC), and syndromic OKC. METHODS: Formalin-fixed paraffin-embedded tissue blocks of histopathologically diagnosed cases of OOC, OKC, syndromic OKC, normal buccal mucosa (NBM), and oral squamous cell carcinoma (OSCC) were examined for immunohistochemical expression of cortactin. Clear brown cytoplasmic and membranous staining was considered positive. RESULTS: A statistically significant difference was observed between OOC and syndromic OKC (p < 0.001), as well as between sporadic OKC and syndromic OKC (p < 0.001). Although not statistically significant, the expression of cortactin was slightly higher in the basal layer of NBM (mean = 0.47), OOC (mean = 0.27), sporadic OKC (mean = 0.47) syndromic OKC (mean = 1.53), and OSCC (mean = 0.67) than in the parabasal layers of NBM (mean = 0.27), OOC (mean = 0.20), sporadic OKC (mean = 0.47), syndromic OKC (mean = 1.27), and OSCC (mean = 0.60). CONCLUSION: The expression of cortactin in the basal layer may suggest the formation of invadopodia in the basal layer where the invasion mechanism occurs. This finding is further supported by the higher localization of cortactin in areas of epithelial budding and daughter cysts in syndromic OKC, thereby reaffirming its possible association with recurrence.

New diagnostic molecular markers and biomarkers in odontogenic tumors.

Odontogenic tumors comprised of complex heterogeneous lesions that diverse from harmatomas to malignant tumors with different behavior and histology. The etiology of odontogenic tumors is not exactly determined and pathologists deal with challenges in diagnosis of odontogenic tumors because they are rare and obtained experiences are difficult to evaluate. In this study, we describe immunohistochemical and molecular markers in diagnosis of odontogenic tumors besides advanced diagnostic technique. Immunohistochemical features of odontogenic tumors beside the clinical features and radiological finding can help us to determine the correct diagnosis. Although these markers are neither specific nor sensitive enough, but analysis of gene expression provides definitive confirmation of diagnosis. In addition, "-omics" technology detected specific molecular alternation associated with etiology such as genomics, epigenomics, transcriptomics, proteomics and metabolomics. The post transcriptional events such as DNA methylation and chromatin remodeling by histone modification affect the changes in epigenome. Furthermore, non-coding RNAs like micro-RNAs, long noncoding RNA (lncRNA) and small non-coding RNA (snoRNA) play regulatory role and impact odontogenesis. Molecular marker propose their potential role in etiopathogenesis of odontogenic tumors and suitable candidate in diagnostic, prognostic and therapeutic approaches in addition to patient management. For future evaluations, organoid represents in vitro tumor model-study for tumor behavior, metastasis and invasion, drug screening, immunotherapy, clinical trial, hallmarks association with prognosis and evolution of personalized anti-cancer therapy. Moreover, organoid biobank help us to check genetic profile. We think more investigation and studies are needed to gain these knowledges that can shift therapeutic approaches to target therapy.

Should the solid variant of odontogenic keratocyst and keratoameloblastoma be classified as the same entity? A clinicopathological analysis of nine cases and a review of the literature.

The solid variant of odontogenic keratocyst (SOKC) is an extremely rare odontogenic lesion, which remains poorly defined even in the 2017 World Health Organization odontogenic tumour classification. It is difficult to distinguish between SOKC and so called keratoameloblastoma (KAB), both rare lesions that have similarities in clinical, histological and biological characteristics. Here, we report clinicopathological data and results of molecular analysis of nine cases with a literature review. First, they were compared to previously reported cases of SOKC and/or KAB, and many overlaps were found in clinical and pathological characteristics. Second, we performed PCR analysis for BRAF V600E mutation. Although ameloblastoma-like epithelia were often encountered, none exhibited BRAF V600E mutation, which has been reported to occur frequently in ameloblastomas but not in odontogenic keratocysts (OKCs). One of two cases of SOKC in the present series from which fresh frozen tissue specimens were available was found to harbour PTCH1 mutations, indicating that these were more likely to be a subtype of OKC. Moreover, we also examined the differences between SOKC and primary intraosseous carcinoma (PIOC) with regard to the expression of cytokeratins (pan-CK, CK5/6, CK7, CK8/18, CK10, CK14 and CK19), p53 and Ki-67. The proportions of p53-and Ki-67-positive cells were significantly higher in PIOC than in SOKC. These findings suggest that immunostaining for p53 and Ki-67 would be useful to differentiate between SOKC and PIOC. We also conducted a review of SOKC and KAB cases reported in the English language literature.

BDNF/TrkB/Akt Signaling Pathway Epithelial Odontogenic Tumors and Keratocyst: An Immunohistochemical Study Comparative With Dental Germs.

Odontogenic lesions (OL) are an important group of oral and maxillofacial diseases represented by odontogenic cysts, benign, and malignant tumors. The brain-derived neurotrophic factor (BDNF)/ tropomyosin receptor kinase B (TrkB) signaling pathway has multiple biological actions and has been identified as an important pathway in the proliferation, invasion, and survival of different epithelial tumors. Its role in the development of OL, however, has so far been unexplored. Our aim was to evaluate the BDNF/TrkB/Akt/p-RPS6 signaling pathway in OL of epithelial origin. This cross-sectional study comprised 3 cases of tooth germs, 25 cases of odontogenic keratocyst (OK), 29 cases of ameloblastoma (Am), and 6 cases of ameloblastic carcinoma. Immunohistochemical staining for BDNF, TrkB, p-Akt, and p-RPS6 was performed. OLs were evaluated according to the pattern of immunohistochemical expression in epithelial cells and by semiquantitative scores that considered the intensity of staining and percentage of positive cells. BDNF stromal expression was also assessed. No significant differences were observed with respect to the percentage of positive cases for all markers. Regarding the immunoreactive scores, BDNF and p-RPS6 expressions were similar in the odontogenic epithelium of all OL. However, TrkB and p-Akt were overexpressed in OK compared with ameloblastic carcinoma. In Am, epithelial BDNF was significantly higher compared with stromal expression. In conclusion, BDNF seems to participate in the development of cystic, benign, and malignant odontogenic epithelium to similar degrees. The acquisition of the invasive or malignant phenotype in odontogenic neoplasms is not associated with alterations in the BDNF/TrkB/Akt/RPS6 axis, which could be implicated in the differentiation process.

Assessment of Tumor Angiogenesis by Expression of CD 105 in Ameloblastoma, Odontogenic Keratocyst and Central Giant Cell Lesion.

BACKGROUND: Angiogenesis is critical for tumor growth and reflects the aggressive behavior of invasive odontogenic lesions [like Ameloblastoma (AM), Odontogenic Keratocyst (OKC) and Central giant cell lesion (CGCL)]. Mean vascular density (MVD) shows the angiogenic potential and CD105 is an ideal endothelial biomarker due to its specificity to new blood vessels for MVD detection. The aim of the study was to compare the MVD (angiogenic potential) among AM, OKC and CGCL in comparison to Pyogenic Granuloma (PG) using CD105 biomarker. METHODS: Sixty-four primary cases of odontogenic invasive tumors (AM, OKC and CGCL) and PG, diagnosed clinically and histologically were included in the study, with 16 samples in each group. Tissue samples of peripheral AM, Peripheral GCL of jaws, malignant AM, and specimen with insufficient tissue were excluded. Tissue sections were embedded, processed and stained using Hematoxylin and Eosin (H and E). Immunohistochemistry was performed using antibodies against CD105, with positive brown cytoplasmic staining in the endothelial cells of neo-vasculature. Distinct countable, positively stained endothelial cell or clusters were evaluated under light microscope for identification of MVD. ANOVA and t-test were applied for statistical analysis of data. RESULTS: Highest MVD was displayed in CGCL (32.99±0.77) and the minimum was observed in OKC (7.21± 0.75) respectively. CGCL showed significantly higher MVD to AM, OKC and PG lesions (p <0.05). AM (8.07± 0.36) and Odontogenic Keratocyst (7.21± 0.75) showed comparable MVD, which was lower than PG (14.7± 0.96) and CGCL vascular density (p < 0.01) respectively. CONCLUSION: CGCL was most aggressive, with highest MVD among the investigated odontogenic lesions (OKC, AM and PG). The proliferative aggressive behavior of Odontogenic Keratocyst is comparable to AM due to comparable mean vascular density.
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Hypoxia and proangiogenic proteins in human ameloblastoma.

Ameloblastomas are epithelial odontogenic tumours that, although benign, are locally invasive and may exhibit aggressive behaviour. In the tumour microenvironment, the concentration of oxygen is reduced, which leads to intratumoral hypoxia. Under hypoxia, the crosstalk between the HIF-1α, MMP-2, VEGF, and VEGFR-2 proteins has been associated with hypoxia-induced angiogenesis, leading to tumour progression and increased invasiveness. This work showcases 24 ameloblastoma cases, 10 calcifying odontogenic cysts, and 9 dental follicles, used to investigate the expression of these proteins by immunohistochemistry. The anti-HIF-1α, anti-MMP-2, anti-VEGF, and anti-VEGFR-2 primary antibodies are used in this work. The results have been expressed by the mean grey value after immunostaining in images acquired with an objective of 40×. The ameloblastoma samples showed higher immunoexpression of HIF-1α, MMP-2, VEGF, and VEGFR-2 when compared to the dental follicles and calcifying odontogenic cysts. Ameloblastomas show a higher degree of expression of proteins associated with intratumoral hypoxia and proangiogenic proteins, which indicates the possible role of these proteins in the biological behaviour of this tumour.

Immunohistochemical expression of p53 and murine double minute 2 protein in odontogenic keratocyst versus variants of ameloblastoma.

INTRODUCTION: Oncogenes and tumor suppressor genes play a major role in cancer formation, growth, and progression. One of the important findings in this area is that murine double minute 2 (MDM2) oncogene is a negative regulator of wild-type p53. In tumors, expressing wild-type p53, inhibition of MDM2 expression will stabilize p53 and allow it to perform its proapoptotic function, while simultaneously preventing MDM2 from exerting its p53-independent oncogenic effects. The intracellular levels of p53 are tightly regulated by MDM2, as it is a key player in autoregulatory feedback loop under nonstressed conditions. The p53-MDM2 relationship is vital not only for essential functions of the cell, but it also appears to be an integrated part of the complex cellular network which supports the importance of this affair and is a hallmark for its coexistence. SUBJECTS AND METHODS: This study was designed to identify immunohistochemically the expression of p53 and MDM2 gene using monoclonal antibody in 60 cases of formalin-fixed paraffin-embedded tissue blocks, of which 20 cases were of solid multicystic ameloblastoma (SMA), 20 cases were of odontogenic keratocyst (OKC), and 20 cases were of unicystic ameloblastoma (UA). RESULTS: Immunoexpression of p53 and MDM2 was highest in OKC followed by SMA and was minimum in UA. Further results showed positive correlation between both the molecules. CONCLUSION: The studied showed that the relationship has a significant role in cancer etiology and progression and therefore is an important topic for future research which should help in the development of new therapeutic agent against cancer.

Malignant fibrous histiocytoma - a case report.

Fibrous histiocytoma is a mesenchymal neoplasm with benign and malignant varieties. This tumor mainly affects the skin of extremities in adults and may on rare occasions affect the oral cavity. The tumor has radiographic features in very rare cases. The present case report aims to conduct a clinicopathological-radiographic and immunohistochemical assessment and treatment of a patient with this lesion.

IKKß overexpression together with a lack of tumour suppressor genes causes ameloblastic odontomas in mice.

Odontogenic tumours are a heterogeneous group of lesions that develop in the oral cavity region and are characterized by the formation of tumoural structures that differentiate as teeth. Due to the diversity of their histopathological characteristics and clinical behaviour, the classification of these tumours is still under debate. Alterations in morphogenesis pathways such as the Hedgehog, MAPK and WNT/ß-catenin pathways are implicated in the formation of odontogenic lesions, but the molecular bases of many of these lesions are still unknown. In this study, we used genetically modified mice to study the role of IKKß (a fundamental regulator of NF-κB activity and many other proteins) in oral epithelial cells and odontogenic tissues. Transgenic mice overexpressing IKKß in oral epithelial cells show a significant increase in immune cells in both the oral epithelia and oral submucosa. They also show changes in the expression of several proteins and miRNAs that are important for cancer development. Interestingly, we found that overactivity of IKKß in oral epithelia and odontogenic tissues, in conjunction with the loss of tumour suppressor proteins (p53, or p16 and p19), leads to the appearance of odontogenic tumours that can be classified as ameloblastic odontomas, sometimes accompanied by foci of secondary ameloblastic carcinomas. These tumours show NF-κB activation and increased ß-catenin activity. These findings may help to elucidate the molecular determinants of odontogenic tumourigenesis and the role of IKKß in the homoeostasis and tumoural transformation of oral and odontogenic epithelia.

Podoplanin Expression in Odontogenic Keratocysts Associated or not Associated With Nevoid Basal Cell Carcinoma Syndrome.

BACKGROUND: Podoplanin is a transmembrane glycoprotein expressed on various normal or neoplastic cells. Some studies have shown that podoplanin promotes the migration and invasion of tumor cells. This study evaluated a podoplanin expression in Odontogenic Keratocysts (OKs) associated or not associated with Nevoid Basal Cell Carcinoma Syndrome (NBCCS) and in Orthokeratinized Odontogenic Cysts (OOCs). MATERIALS AND METHODS: A total of 50 lesions were obtained in this study, 28 OKs, 18 OKs associated with NBCCS, and 4 OOCs. Immunohistochemical expression of podoplanin in epithelial cells was evaluated using the following score: (a) intensity of immunostaining: (0: absent, 1: weak, 2: moderate, 3: strong, and 4: very strong) and (b) number of positively cells (0: 0%, 1: <25%, 2: 25% to 50%, 3: 50% to 75%, and 4: >75%). The final score was determined by adding the scores of a and b and ranged from 0 to 8 (0: absent, 1 to 4: weak, and 5 to 8: strong). RESULTS: Podoplanin expression was significantly stronger in the basal layer OKs and NBCCS lesions. Further, podoplanin expression was the highest in the suprabasal layer of NBCCS lesions, followed by the suprabasal layers of OK and OOC lesions. CONCLUSIONS: Podoplanin expression is different in lesions of different biological behaviors. Podoplanin seems to play a role in cell proliferation and migration.

Immunohistochemical analysis of MMP-13 and EMMPRIN in epithelial odontogenic lesions.

PURPOSE: To investigate the contribution of MMP-13 in tumor aggressiveness, by acting on the reorganization of the extracellular matrix, regulating the biological activity of cytokines in odontogenic epithelial lesions, as well as to evaluate the role of EMMPRIN as an inducer of MMP-13. METHODS: Twenty solid ameloblastomas (SAs), 10 unicystic ameloblastomas (UAs), 20 odontogenic keratocysts (OKCs), and 20 adenomatoid odontogenic tumors (OATs) were selected. The expression of MMP-13 and EMMPRIN was evaluated in epithelial/connective tissue by determining the score of immunoreactive cells. RESULTS: Higher concentration of MMP-13 was observed in epithelium of SAs and OKCs (p = 0.316), while in connective, MMP-13 was more expressed in OKCs and UAs (p = 0.213). OKCs exhibited the highest immunoreactivity score for EMMPRIN in the epithelium (p = 0.091). In connective tissue, a larger number of immunoreactive cells were observed in OKCs and UACs (p = 0.357). There was a moderate correlation (r = 0.343/p = 0.004) between MMP-13/EMMPRIN in epithelium and strong correlation (r = 0.474/p < 0.001) in connective tissue. CONCLUSION: We suggest that the OKCs, SAs and UAs presented greater immunoexpression for MMP-13 and EMMPRIN, since they were lesions of more aggressive behavior, with smaller expressions in the AOTs that are admittedly indolent. However, we did not find a statistically significant difference between the expression of MMP-13 and EMMPRIN in lesions studied. The positive correlation found between MMP-13 and EMMPRIN in the epithelial and connective tissue of odontogenic lesions analyzed, seems to be related to the role of EMMPRIN as an inducer of MMP-13 expression.

The dilemma of extensive unilocular radiolucent lesions of the jaws - value of immunohistochemistry as a diagnostic marker and prognostic Indicator.

INTRODUCTION: Large Unilocular radiolucent lesions of the jaws often present a dilemma to both, the Oral Pathologist and the Maxillofacial surgeon with regards to their accurate diagnosis as well as their most appropriate treatment modality. A precise identification as to whether the lesion is a cyst or a tumor is imperative before any treatment is instituted. Once the correct diagnosis and likely prognosis are established, a management protocol can be planned which will completely eliminate the lesion, while at the same time, ensure least possible morbidity for the patient, such as pathological jaw fractures, persisting neurological deficits, esthetic deformity, functional debility, recurrence/persistence of the lesion, etc. AIM & OBJECTIVES: To establish the value of Immunohistochemistry (IH) as a Diagnostic marker and Prognostic indicator for extensive Unilocular radiolucent lesions of the jaws. To assess its role as an adjunct to Histopathological Examination (HPE) in distinguishing Odontogenic tumours from the cysts, by identifying the former using IH Tumor Markers; and in aiding in selection of the most appropriate and effective treatment option for each of such ambiguous lesions, based on their prognosis as indicated by the expression of lH Cell Proliferation Markers. MATERIALS AND METHOD: Thirty cases of large Unilocular Radiolucent lesions of the jaws (Maxilla/Mandible) were managed over a period of three years. Histopathological examination (HPE) and Immunohistochemical (IH) analysis were carried out of the biopsy specimens in all the cases. Calretinin, an Immunohistochemical Tumor marker, was used to distinguish between Odontogenic cysts and tumours. Ki-67 and Proliferating Cell Nuclear Antigen (PCNA), Immunohistochemical Cell Proliferation markers, provided information on the aggressive potential of the lesions. On the basis of the above information, an appropriate management protocol was established for each of these different lesions. Nerve sparing enucleation and curettage was employed for the established cases of Odontogenic Cysts; Enucleation and curettage, peripheral ostectomy, followed by chemical cauterization was employed for the Unicystic Ameloblastomas and other Odontogenic tumours with a low Ki-67 and PCNA Proliferation Index (PI)/Labelling index (LI ≤ 3); Marginal resection was carried out for the tumours with a higher Labelling Index (LI >3 ≤5), and Segmental resection (including partial/complete Maxillectomy, Hemimandibulectomy with/without disarticulation) for the aggressive pathologies with high Labelling Index (LI > 5). RESULTS: Of the thirty cases of large Unilocular radiolucent lesions of the Maxilla and Mandible, thirteen were diagnosed as Dentigerous cysts, one as Dentigerous cyst showing Ameloblastomatous transformation; two as Unicystic Ameloblastomas, one as the Mural variant of Unicystic Ameloblastoma; four as Follicular Ameloblastomas, two as Plexiform Ameloblastomas; four as Acanthomatous Ameloblastomas; one as Ameloblastic Fibroma and two as Adenomatoid Odontogenic Tumours. The predictive and prognostic indication of the Immunohistochemical markers correlated well with the post treatment findings. CONCLUSION: In cases of extensive Unilocular lesions of the jaws, where ambiguity often exists in both diagnosis and appropriate treatment plan to be employed, Immunohistochemistry can serve as an invaluable tool in establishing the precise diagnosis, guiding the treatment plan, as well as indicating the likely prognosis of these lesions.

Notch Signaling Affects Oral Neoplasm Cell Differentiation and Acquisition of Tumor-Specific Characteristics.

Histopathological findings of oral neoplasm cell differentiation and metaplasia suggest that tumor cells induce their own dedifferentiation and re-differentiation and may lead to the formation of tumor-specific histological features. Notch signaling is involved in the maintenance of tissue stem cell nature and regulation of differentiation and is responsible for the cytological regulation of cell fate, morphogenesis, and/or development. In our previous study, immunohistochemistry was used to examine Notch expression using cases of odontogenic tumors and pleomorphic adenoma as oral neoplasms. According to our results, Notch signaling was specifically associated with tumor cell differentiation and metaplastic cells of developmental tissues. Notch signaling was involved in the differentiation of the ductal epithelial cells of salivary gland tumors and ameloblast-like cells of odontogenic tumors. However, Notch signaling was also involved in squamous metaplasia, irrespective of the type of developmental tissue. In odontogenic tumors, Notch signaling was involved in epithelial-mesenchymal interactions and may be related to tumor development and tumorigenesis. This signaling may also be associated with the malignant transformation of ameloblastomas. Overall, Notch signaling appears to play a major role in the formation of the characteristic cellular composition and histological features of oral neoplasms, and this involvement has been reviewed here.

Cell proliferation proteins and aggressiveness of histological variants of ameloblastoma and keratocystic odontogenic tumor.

Tumors that originate from the epithelium of the odontogenic apparatus are classified as benign or malignant. The proliferative activity could provide a basis for differences in the biologic behavior among the histological variants of ameloblastoma (AM) and keratocystic odontogenic tumor (KCOT). We examined 32 solid AM and 18 KCOT cases. The AM sample comprised 16 cases of follicular AM, six cases of unicystic AM, eight cases of plexiform AM and two cases of acanthomatous AM. Sections were stained with the Ki-67 antibody. Ten representative fields were selected randomly in each section. For AM, peripheral tall columnar cells of tumor islands/nests/cords were selected. For KCOT, fields were selected in the basal and the suprabasal region of the epithelial lining. We counted the average number of Ki-67 positive cells/field for AM and KCOT. AM exhibited Ki-67 expression in peripheral tall columnar cells, whereas KCOT exhibited Ki-67 expression in the basal and suprabasal layer. No significant difference between AM and KCOT was observed; the cellular proliferative activity varied among the subtypes. No significant difference in Ki-67 expression in acanthomatous, cystic and follicular types of AM was observed, although the plexiform type exhibited significantly higher levels than the other three types. High expression of Ki-67 could be a useful prognostic marker for proliferative activity and a prognostic indicator for recurrence rate of AM and KCOT.

The importance of BRAF-V600E mutation to ameloblastoma metabolism.

BACKGROUND: Ameloblastoma is a locally infiltrative, aggressive epithelial odontogenic neoplasm. BRAF-V600E mutation is frequently found in this tumor and has a pivotal role in its pathogenesis, but the consequences of this alteration need to be addressed. An untargeted metabolomics approach was applied to verify whether metabolic disturbances are related to tumor biology and whether BRAF-V600E mutation contributes to these alterations. METHODS: Formalin-fixed and paraffin-embedded tissue specimens from thirteen ameloblastoma and six dental follicles were included in this study. BRAF mutational status was determined by competitive allele-specific real-time PCR. Metabolite extracts were analyzed using gas chromatography coupled to mass spectrometry. Univariate and multivariate statistical methods were employed to compare the metabolic profiles of the samples. RESULTS: The abundance of eleven metabolites was significantly higher in ameloblastoma in relation to dental follicles, including amino acids, fatty acids, carbohydrates, inorganic acids, and organoheterocyclic compounds. The presence of BRAF-V600E mutations in ameloblastoma was related to decreased levels of glycerol in comparison with tumors carrying only wild-type alleles of this gene. No metabolic differences were observed between recurrent and primary manifestations of ameloblastoma. CONCLUSIONS: Ameloblastoma exhibits a distinct metabolic profile from normal odontogenic epithelium. BRAF-V600E may contribute to metabolic alterations in ameloblastoma. Collectively, our findings suggest that metabolic alterations might play a role in tumor pathogenesis.

Comparison of fatty acid synthase and cyclooxygenase-2 immunoexpression in embryonal, benign, and malignant odontogenic tissues.

OBJECTIVES: The aim of this study was to analyze the immunohistochemical expression of fatty acid synthase (FASN) and cyclooxygenase-2 (COX-2) in tooth germ (TG), ameloblastoma (AM), ameloblastic carcinoma (AC), ameloblastic fibroma (AF), and ameloblastic fibrosarcoma (AFS). STUDY DESIGN: Immunohistochemistry for FASN and COX-2 was performed in 10 TG, 44 AM, 10 AC, 9 AF, and 5 AFS specimens. The results were analyzed by using the immunoreactive score (IRS) and Kruskal-Wallis test followed by Dunn's post-test. RESULTS: Most TG specimens were strongly positive for FASN, whereas COX-2 was weak or negative. All AM and AC specimens expressed both proteins. In AF specimens, FASN and COX-2 were variably expressed in the epithelium and negative in the mesenchyme. In AFS specimens, FASN was strongly positive in the malignant mesenchyme and variable in the epithelium; COX-2 was focal or weak in both components. FASN expression showed significant differences in the following comparisons: TG vs AC, AM vs AC, and AF vs AFS. Differences in COX-2 were significant when comparing TG specimens with AM, AC, and AF specimens. CONCLUSIONS: The results suggest that FASN and COX-2 overexpression may have a role in the pathogenesis of AM and AC, whereas in AFS, FASN seems to be mainly involved. Further studies are necessary to clarify these mechanisms and their clinical implications.

Stromal Expression of CD10 by Immunohistochemistry in Odontogenic Keratocyst (OKC), Dentigerous and Radicular Cysts and Its Correlation with Local Recurrence and Aggressive Behaviour

Objective: To assess and compare the stromal expression of CD10 in OKC, dentigerous and radicular cysts. Materials and Methods: This comparative, cross sectional study was conducted at Armed Forces Institute of Pathology (AFIP), Rawalpindi, from Jan 2017 to Dec 2017. Total sixty cases comprising 20 of each OKC, Dentigerous and Radicular cysts were included in this study. Hematoxylin and eosin (H and E) sections were performed followed by immunohistochemical staining for CD10 antibody. Expression of CD10 was evaluated and compared. Results were analyzed by using SPSS version 20.0. Chi Square test was performed with P value < 0.05 was considered as significant. Results: A total of 60 cases, 20 of each OKC, dentigerous and radicular cysts were taken. In our study, 38 (63.3%) male and 22 (36.7%) female patients with the mean age of 32 ± 15 (mean ± SD) were included. Percentage of CD10 positive cells were highest in sub-epithelial stroma of OKC (95% cases) as compared to radicular and dentigerous cysts (60 and 70%) with highest number of cases showing intense staining in OKC 13(65%) as compared to other odontogenic cysts i-e 4(20%) and 2 (10%) respectively. There was a statistically significant association between odontogenic cysts and proportional score, intensity score and combined score of stromal CD10 expression (P=0.009, p=0.001 and p=0.000). Conclusion: In this study, we found that highest stromal CD10 expression in OKC as compared to dentigerous and radicular cyst, which might be due to aggressive behaviour and increased risk of recurrence in OKC. Expression of CD10 marker will further aid the clinician to plan appropriate surgical intervention and keep regular follow-ups to identify recurrences.