Surrogate Immunohistochemical Markers of Proliferation and Embryonic Stem Cells in Distinguishing Ameloblastoma from Ameloblastic Carcinoma.

PURPOSE: The current study aimed to investigate the use of surrogate immunohistochemical (IHC) markers of proliferation and stem cells to distinguish ameloblastoma (AB) from ameloblastic carcinoma (AC). METHODS: The study assessed a total of 29 ACs, 6 ABs that transformed into ACs, and a control cohort of 20 ABs. The demographics and clinicopathologic details of the included cases of AC were recorded. The Ki-67 proliferation index was scored through automated methods with the QuPath open-source software platform. For SOX2, OCT4 and Glypican-3 IHC, each case was scored using a proportion of positivity score combined with an intensity score to produce a total score. RESULTS: All cases of AC showed a relatively high median proliferation index of 41.7%, with statistically significant higher scores compared to ABs. ABs that transformed into ACs had similar median proliferation scores to the control cohort of ABs. Most cases of AC showed some degree of SOX2 expression, with 58.6% showing high expression. OCT4 expression was not seen in any case of AC. GPC-3 expression in ACs was limited, with high expression in 17.2% of ACs. Primary ACs showed higher median proliferation scores and degrees of SOX2 and GPC-3 expression than secondary cases. Regarding SOX2, OCT4 and GPC-3 IHC expression, no statistically significant differences existed between the cohort of ABs and ACs. CONCLUSION: Ki-67 IHC as a proliferation marker, particularly when assessed via automated methods, was helpful in distinguishing AC from AB cases. In contrast to other studies, surrogate IHC markers of embryonic stem cells, SOX2, OCT4 and GPC-3, were unreliable in distinguishing the two entities.

NKG2D (Natural Killer Group 2, Member D) ligand expression and ameloblastoma recurrence: a retrospective immunohistological pilot study.

BACKGROUND/PURPOSE: This retrospective immunohistological pilot study aimed to investigate the influence of natural killer group 2, member D (NKG2D) ligand expression on ameloblastoma recurrence after surgical resection. It also aimed to elucidate additional clinical factors that could serve as predictors of ameloblastoma recurrence. MATERIALS AND METHODS: This study included 96 patients who were histologically diagnosed with ameloblastoma after surgical resection. The expression of NKG2D ligands, including UL16-binding proteins (ULBPs) 1-3 and major histocompatibility complex class I chain-related molecule (MIC) A/B, was evaluated in formalin-fixed paraffin-embedded tumor tissues via immunohistochemistry assays. Furthermore, the patients' electronic medical records were reviewed. Multivariate Cox regression analysis was conducted, and data were expressed as adjusted hazard ratios [HRs] with 95% confidence intervals [95% CIs]. RESULTS: Multivariate analysis revealed that recurrent tumors (ref.: primary; adjusted HR [95% CI]: 2.780 [1.136, 6.803], p = 0.025) and positive MICA/B expression (ref.: negative; adjusted HR [95% CI]: 0.223 [0.050, 0.989], p = 0.048) independently affected recurrence-free survival in ameloblastoma. CONCLUSION: This study identified recurrent cases and loss of MICA/B expression as independent predictors of early ameloblastoma recurrence following surgical resection. The findings suggest that decreased MICA/B expression might undermine NKG2D-mediated tumor immunosurveillance, thereby influencing early recurrence.

MMP13 Expression and Activity Suggest Its Role in Bone Resorption in Ameloblastomas.

BACKGROUND: Ameloblastoma is a locally destructive benign odontogenic tumor. While the neoplastic cells of conventional ameloblastoma can infiltrate the connective tissue and bone, in unicystic ameloblastoma the epithelium is encapsulated. The mechanisms driving ameloblastoma's bone resorption remains unclear. METHODS: RNA sequencing (RNA-seq) was performed in a discovery cohort of conventional ameloblastoma, and pathway enrichment analysis was carried out. mRNA levels of MMP13, a gene associated with bone resorption, were assessed using RT-qPCR in a larger cohort of conventional ameloblastoma and in unicystic ameloblastoma. Zymogram gels and the immunoexpression profile of collagenase 3 (encoded by MMP13 gene) were evaluated as well. RESULTS: Enriched pathways related to bone mineralization and upregulation of MMP13 were observed in ameloblastomas. Collagenolytic activity of collagenase 3 was detected in the tumor lysates. Collagenase 3 immunopositivity was observed in ameloblastomatous epithelium infiltrating the fibrous capsule of unicystic ameloblastoma. At the tumor-bone interface, collagenase 3 expression was detected in stromal cells, osteoblasts, and osteocytes. CONCLUSION: The results indicate a potential involvement of MMP13 in ameloblastoma-related bone resorption and progression.

Differential Expression of Immunohistochemical Markers in Ameloblastoma & Ameloblastic Carcinoma: A Systematic Review and Meta-analysis of observational studies.

Background: Differentiating between ameloblastoma (AB) and ameloblastic carcinoma (AC) is difficult, especially when AB has atypical cytological characteristics or an uncommon clinical history. This systematic review and meta-analysis aimed to elucidate the differential expression of immunohistochemical markers between AB and AC. Methods: We conducted a thorough search of PUBMED and SCOPUS according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines to identify cross-sectional studies that compared the expression of immunohistochemical markers in AB and AC. We used a random-effects model to analyze the risk ratios and their corresponding 95% confidence intervals (CIs). The quality of the included studies was assessed using the Newcastle-Ottawa scale. The Egger's test was used to assess publication bias. Results: In total, 301 articles were identified. After excluding irrelevant titles and abstracts, 86 articles were selected for full-text review. We categorized the 41 markers into proliferative and non-proliferative markers. Among non-proliferative markers, nuclear markers were differentially expressed in AB and AC. SOX2 was the only marker that significantly differentiated AB and AC, with an RR of -0.19 (CI 0.10-0.36, I2=0). Conclusion: The current evidence suggests the significance of SOX2 in differentiating between AB and AC, warranting prospective confirmation in well-defined extensive studies. We highlight the paucity of high-quality replicated studies of other markers in this field. Collaborative efforts with standardized techniques are necessary to generate clinically useful immunohistochemical markers.

Tumor microenvironment of ameloblastoma with a focus on osteoclastogenesis, cell migration, and malignant transformation.

BACKGROUND: Odontogenic tumors arise in the jawbone and originate from cells associated with tooth development. Therefore, understanding odontogenic tumors requires knowledge of all aspects of dental research, including tooth development and eruption. Ameloblastoma is the most common odontogenic tumor. HIGHLIGHT: Although a benign tumor, ameloblastoma progresses with marked jawbone resorption. Because of its locally aggressive features, it can be treated surgically by resecting the surrounding bone. From a molecular pathology perspective, several genetic mutations and dysregulated signaling pathways involved in ameloblastoma tumorigenesis have been identified. Histopathologically, ameloblastomas consist of peripheral ameloblast-like cells and an inner stellate reticulum. The stromal region consists of fibrovascular connective tissue, showing a characteristic sparse myxoid histology. In general, the tumor microenvironment, including the surrounding non-tumor cells, contributes to tumorigenesis and progression. In this review, we focus on the tumor microenvironment of ameloblastomas. In addition, we present some of our recent studies on osteoclastogenesis, tubulin acetylation-induced cell migration, and hypoxia-induced epithelial-mesenchymal transition in ameloblastomas. CONCLUSION: Further research on ameloblastomas can lead to the development of new treatments and improve patients' quality of life.

Comprehensive insights into the understanding of hypoxia in ameloblastoma.

Hypoxia is characterized by a disparity between supply and demand of oxygen. The association between hypoxia and head and neck tumors is a topic of significant interest. Tumors frequently encounter areas with inadequate oxygen supply, resulting in a hypoxic microenvironment. Ameloblastoma is one of the most common benign odontogenic tumors of the maxillofacial region. It is a slow-growing but locally invasive tumor with a high recurrence rate. The literature has demonstrated the correlation between hypoxia and ameloblastoma, revealing a discernible link between the heightened expression of hypoxic markers in low oxygen conditions. This association is intricately tied to the tumoral potential for invasion, progression, and malignant transformation. Hypoxia profoundly influences the molecular and cellular landscape within ameloblastic lesions. The present review sheds light on the mechanisms, implications, and emerging perspectives in understanding this intriguing association to clarify the dynamic relationship between hypoxia and ameloblastoma.

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.

Immunohistochemical evaluation of IL-1ß, IL-6, TNF-α and IL-17 cytokine expression in peripheral giant cell granuloma and peripheral ossifying fibroma of the jaws.

OBJECTIVE: To examine and compare the immunohistochemical expressions of IL-1ß, IL-6, IL-17 and TNF-α in peripheral giant cell granuloma (PGCG) and peripheral ossifying fibroma (POF). DESIGN: The study included 20 POF and 20 PGCG cases diagnosed at the Pathology Department of Eskisehir Osmangazi University Medical Faculty. Hematoxylin & Eosin-stained slides obtained from each biopsy specimen were re-evaluated, and IL-1ß, IL-6, IL-17 and TNF-α antibodies were investigated immunohistochemically. While staining in stromal cells was examined in POF cases, staining in both stromal spindle cells and multinucleated giant cells was evaluated in PGCG cases. An immunoreactivity score was established for each case by evaluating the staining percentage and intensity for each individual case. The significance level was set at 5% (p < 0.05). RESULTS: The level of IL-6 and TNF-α expressions in the multinucleated giant cells in PGCG lesions was found higher than that in stromal cells (p < 0.005 and p < 0.000, respectively). In PGCG lesions, there was no significant difference between giant cells and stromal cells in terms of IL-1ß and IL-17 expression levels. There was no significant difference between PGCG and POF lesions in terms of IL-1ß and IL-6 expression. TNF-α expression levels were significantly higher in spindle cells of PGCG lesions than that of POF lesions (p < 0.00). However, IL-17 expression levels were significantly lower in PGCG lesions than in POF lesions (p < 0.05). CONCLUSION: The study results showed that TNF-α expression was significantly higher in PGCG lesions and IL-17 expression in POF lesions. IL-1ß, IL-6, IL-17 and TNF-α are involved in the pathogenesis of both PGCG and POF lesions.

αTAT1-induced tubulin acetylation promotes ameloblastoma migration and invasion.

Ameloblastoma (AB) is the most common benign epithelial odontogenic tumor occurring in the jawbone. AB is a slowly growing tumor but sometimes shows a locally invasive and an aggressive growth pattern with a marked bone resorption. In addition, the local recurrence and distant metastasis of AB also sometimes occurs, which resembles one of the typical malignant potentials. From these points of view, to understand better the mechanisms of AB cell migration or invasion is necessary for the better clinical therapy and improvements of the patients' quality of life. Microtubules in eukaryotic cells reveal the shape of hollow cylinders made up of polymerized alpha (α)- and beta (ß)-tubulin dimers and form the cytoskeleton together with microfilaments and intermediate filaments. Microtubules play important roles in cell migration by undergoing assembly and disassembly with post-translational modifications. Stability of microtubules caused by their acetylation is involved in cell migration. In this study, we investigated the expression and distribution of acetylated α-tubulin and alpha-tubulin N-acetyltransferase 1 (αTAT1), an enzyme which acetylates Lys-40 in α-tubulin, in AB specimens, and analyzed how tubulin was acetylated by αTAT1 activation in a human AB cell line, AM-1. Finally, we clarified that TGF-ß-activated kinase1 (TAK1) was phosphorylated by TGF-ß stimulation, then, induced tubulin acetylation via αTAT1 activation, which subsequently activated the migration and invasion of AB cells.

Comparative transcriptional profiling of canine acanthomatous ameloblastoma and homology with human ameloblastoma.

Ameloblastomas are odontogenic tumors that are rare in people but have a relatively high prevalence in dogs. Because canine acanthomatous ameloblastomas (CAA) have clinicopathologic and molecular features in common with human ameloblastomas (AM), spontaneous CAA can serve as a useful translational model of disease. However, the molecular basis of CAA and how it compares to AM are incompletely understood. In this study, we compared the global genomic expression profile of CAA with AM and evaluated its dental origin by using a bulk RNA-seq approach. For these studies, healthy gingiva and canine oral squamous cell carcinoma served as controls. We found that aberrant RAS signaling, and activation of the epithelial-to-mesenchymal transition cellular program are involved in the pathogenesis of CAA, and that CAA is enriched with genes known to be upregulated in AM including those expressed during the early stages of tooth development, suggesting a high level of molecular homology. These results support the model that domestic dogs with spontaneous CAA have potential for pre-clinical assessment of targeted therapeutic modalities against AM.

Differentiated Immunohistochemical Expression of Osteoclastogenic Markers in Radicular Cyst, Odontogenic Keratocyst, and Ameloblastoma.

The aim of this study was to investigate the osteoclastogenesis process by means of immunohistochemical markers for receptor activator of nuclear factor κB ligand (RANKL), osteoprotegerin (OPG), interleukin-6 (IL-6), and cathepsin K (CTSK) antigens in osteolytic lesions of maxillary bones. The sample consisted of 23 radicular cysts (RC), 25 odontogenic keratocysts (OKC), and 25 ameloblastomas (AM). RANKL was statistically higher in RC (49.6±15.2/53.7±18) and OKC (48.6±15.1/51.4±16.8) when compared with AM (37.2±12.5/36.4±13) in the epithelium and connective tissue. OPG was lower in OKC (34.8±18.5) only in connective tissue when compared with RC (44.5±11.2). The expression of RANKL was statistically higher than OPG in RC (epithelium and connective tissue) and OKC (connective tissue). For IL-6, a statistical difference was observed only in the connective tissue between groups, with higher expression in RC (48.2±15) and lower in OKC (22±11.9). The expression of IL-6 was correlated with the intensity of the inflammatory infiltrate. CTSK was statistically higher in AM (34±19) and OKC (29±13.8) compared with RC (19±10.5). According to the results of the present research the bone resorption in cysts and odontogenic tumors occurs through different mechanisms. The ostoclastogenic process in lesions with aggressive clinical behavior, as AM and OKC, seems to be associated with the expression of CTSK. In contrast, lesions with inflammatory etiology, as RC, the expression of IL-6 seems to have an important role in the bone resorption process. The highest expression of RANKL under the expression of OPG also seems to contribute to the growth mechanism of RC and OKC.

Report of a Rare Case of Spindle Cell Ameloblastic Carcinoma and the Diagnostic Utility of Immunohistochemistry.

Ameloblastic carcinoma is a rare aggressive malignant epithelial odontogenic tumor. The spindle cell variant of ameloblastic carcinoma (SCAC) is exceedingly rare with 15 cases of SCAC having been reported. Therefore, because of the paucity of cases in literature related to SCAC, the biological behavior of the entity has not been well evaluated. Herein the authors report a case of incidentally diagnosed SCAC in a 20-year-old woman identified on imaging as part of the evaluation of a work-related facial injury. Histologically, the tumor had background of cystic ameloblastoma with areas of dense hypercellular spindle cells with short-to-long intersecting fascicles and occasional herringbone pattern intermixed with solid epithelial nests. Both the epithelial and spindle cells were positive for cytokeratin including cytokeratin 19, D2-40, and transducin-like enhancer of split proteins-1 immunohistochemical stains. The patient was followed for 18 months with no evidence of recurrence or metastasis. To the knowledge this is a first case of reporting D2-40 positivity in spindle ameloblastic carcinoma and this immunostain could be used as helpful marker to diagnose this entity.

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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Role of phosphatase and tensin homolog in pathogenesis of ameloblastoma: An immunohistochemical study.

BACKGROUND: Altered molecular signaling pathways in ameloblastoma have been identified to play a pivotal role in the mechanism of oncogenesis, differentiation, and tumor progression. Phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin pathway is one of the signaling pathways that are associated with the pathogenesis of ameloblastoma. Phosphatase and tensin homolog (PTEN) controls cell migration and proliferation. It monitors the level of the Akt and maintains cellular integrity. The present study was aimed to study the immunoexpression of PTEN in ameloblastoma to understand its role in the pathogenesis of ameloblastoma. MATERIALS AND METHODS: Twenty cases of ameloblastoma and ten cases of normal tooth germ were subjected to immunohistochemical staining against PTEN. RESULTS: Strong PTEN immunopositivity was seen in the tooth germs, while weak positivity was seen in the ameloblastoma. The immunoscore for PTEN was calculated by adding the percentage score and the intensity score. Seventeen cases showed the reduced PTEN expression in the epithelial component of ameloblastoma. The unpaired t-test showed a statistically significant difference in the mean PTEN immunoscore in tooth germ and ameloblastoma. CONCLUSION: The study showed reduced PTEN immunoreactivity, which plays a role in the pathogenesis of ameloblastoma, through Akt pathway.

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.

Upregulation of Neural Cell Adhesion Molecule 1 (NCAM1) by hsa-miR-141-3p Suppresses Ameloblastoma Cell Migration.

BACKGROUND Neural cell adhesion molecule 1 (NCAM1; CD56) and E-cadherin are both involved in cell-cell adhesion and cell development processes, and their dysregulation is associated with various tumors. We hypothesized that dysregulated NCAM1 could suppress the invasive behavior of ameloblastoma (AB), and its expression was regulated by miR-141-3p. MATERIAL AND METHODS Real-time qPCR was performed to examine differences in miR-141-3p expression between AB tissues and normal oral tissues (NOMs). The potential target NCAM1 of miR-141-3p was predicted by bioinformatics analysis, which was validated through dual-luciferase assay. The mRNA and protein levels of NCAM1 were detected by real-time qPCR and Western blot, respectively. Furthermore, the expression and distribution of NCAM1 in AB were investigated through immunohistochemical staining, and immunohistochemical staining of E-cadherin was also performed. After overexpression of NCAM1, the migration of AM-1 cells was examined using wound-healing assay. RESULTS Real-time qPCR results confirmed that miR-141-3p was significantly downregulated in AB tissues. According to bioinformatics analysis, NCAM1 was a target of miR-141-3p, which was confirmed by dual luciferase assay. We found that NCAM1 was significantly upregulated in AB tissues at the mRNA and protein levels. Furthermore, NCAM1 and E-cadherin were mainly expressed on the cell membrane of AB. Downregulation of E-cadherin was found in AB tissues. As shown in wound-healing assay results, NCAM1 overexpression significantly inhibited the invasiveness of AM-1 cells. CONCLUSIONS In this study, highly expressed NCAM1 was found in AB, and it suppressed the migration of AB cells and was regulated by miR-141-3p, suggesting its potential value as a therapeutic target for AB.

Differential expression of nicotinamide N-methyltransferase in primary and recurrent ameloblastomas and odontogenic keratocysts.

BACKGROUND: Odontogenic tumours are a group of rare heterogeneous diseases that range from hamartomatous tissue proliferations to benign and malignant neoplasms. Recurrences can occur after 10 years, so long-term clinical and radiological follow-up is required. The study of the molecular mechanisms involved in the development of these lesions is necessary to identify new prognostic markers. In this study, we evaluate the possible role of nicotinamide N-methyltransferase (NNMT) in ameloblastomas (AM) and odontogenic keratocysts (OKC). MATERIALS AND METHODS: A total of 105 surgical specimens of primary and recurrent lesions were obtained from 55 patients (25 AM, 30 OKC). In particular, 50 AMs (25 primary, 25 recurrences) and 55 OKCs (30 primary, 25 recurrences) were retrieved. We carried out immunohistochemical analyses to evaluate the cytoplasmic expression of NNMT, measuring the percentage of positive cells and the value of NNMT expression intensity. RESULTS: NNMT expression was significantly higher in recurrent than primary AMs (P = .0430). This result was confirmed by staining intensity, showing more cases with moderate/intense staining in recurrent AMs (P = .0470). NNMT expression was significantly lower in recurrent than primary OKC (P = .0014). Staining intensity showed more cases with moderate/intense staining in primary OKCs (P = .0276). CONCLUSIONS: This report is the first to evaluate NNMT expression in odontogenic lesions and to demonstrate a differential expression in recurrent AMs and OKCs, suggesting that there is potential for use of NNMT as prognostic marker.

Discovery of novel molecular characteristics and cellular biological properties in ameloblastoma.

Ameloblastoma is a rare odontogenic benign tumor accounting for less than 1% of head and neck tumors. Advanced next generation sequencing (NGS) analyses identified high frequency of BRAF V600E and SMO L412F mutations in ameloblastoma. Despite the existence of whole genomic sequence information from patients with ameloblastoma, entire molecular signature of and the characteristics of ameloblastoma cells are still obscure. In this study, we sought to uncover the molecular basis of ameloblastoma and to determine the cellular phenotype of ameloblastoma cells with BRAF mutations. Our comparative cDNA microarray analysis and gene set enrichment analysis (GSEA) showed that ameloblastoma exhibited a distinct gene expression pattern from the normal tissues: KRAS-responsive gene set is significantly activated in ameloblastoma. Importantly, insulin like growth factor 2 (IGF2), a member of KRAS-responsive genes, enhances the proliferation of an ameloblastoma cell line AMU-AM1 with BRAF mutation. In addition, Toll-like receptor 2 (TLR2) knockdown readily inactivated KRAS-responsive gene sets as well as increases caspase activities, suggesting that TLR2 signaling may mediate cell survival signaling in ameloblastoma cells. Collectively, the findings may help to further clarify the pathophysiology of ameloblastoma and lead to the development of precision medicine for patients with ameloblastoma.

Clinical, histopathologic, subtype, and immunohistochemical analysis of jaw phosphaturic mesenchymal tumors.

Jaw phosphaturic mesenchymal tumors (PMTs) are a rare neoplasm with uncertain histogenesis. This study aimed to clarify the clinical and pathological features of jaw PMTs.We reviewed the clinical records of 39 patients diagnosed with PMTs in the jaws, and investigated clinical and morphologic characteristics, histologic subtypes, and immunophenotypes of all cases.Microscopic analyses revealed 2 major histologic tumor subtypes: "phosphaturic mesenchymal tumors of mixed epithelial and connective tissue" (PMTMECT), and "phosphaturic mesenchymal tumors of mixed connective tissue" (PMTMCT). PMTMECTs and PMTMCTs accounted for 29 and 10 cases of PMTs, respectively. Most PMTMECT diagnoses were made predominantly in males aged <45 years, and the incidence was similar in both the mandible and maxilla. In contrast, patients with PMTMCTs are predominantly females aged ≥45 years, and all tumors were in the mandible. Histologically, PMTMECT had lower cellularity and a more elongated and spindled mesenchymal component with less elaborate intrinsic microvasculature than PMTMCT. Immunohistochemically, the epithelia of all PMTMECTs was immunoreactive for AE1/AE3. Other immunohistochemical staining of PMTMECTs revealed positive expression of vimentin, SATB2, ERG, CD99, Bcl-2, CD56, S-100, D2-40, CD68, SMA, and CD34 in either one or both components. Immunohistochemical staining of PMTMCTs was diffusely positive for vimentin and a varied ratio of positivity for SATB2, ERG, CD99, Bcl-2, CD56, S-100, D2-40, CD68, SMA, and CD34, but negative for AE1/AE3. Most patients were cured by complete resection, except 2 patients who had repeated recurrences, one of which also had multiple metastasis.Jaw PMT can be divided into 2 major histological subtypes. PMTMECTs are more common than are PMTMCTs, and can transform into malignant PMTMCTs during the progression. PMTMECTs were more commonly observed in males and the incidence was similar in both the maxilla and mandible. PMTMCTs were almost always observed in the mandible of females. Compared with PMTMCTs, PMTMECTs have an admixture of epithelial components with less prominent vasculature and lower cellularity. There were no statistically significant differences in the expression of immunohistochemical markers except AE1/AE3 between PMTMECTs and PMTMCTs. However, immunohistochemical markers have great significance for differentiating other mesenchymal tumors.

Metastatic tumors in oral mucosa and jawbones: Unusual primary origins and unusual oral locations.

AIM: To perform clinico-pathological characterization of a large series of oral metastases, collected from 3 main medical centers in Israel and compare findings to data on frequency of primary cancer types in the population. MATERIALS: Pathology archives were searched for cases of metastatic tumors to the oral soft tissues and jawbones, 1990 - 2016. Metastases to the skin of face or to major salivary glands have been excluded. Demographic data and histopathological features were analyzed. RESULTS: Study population included 60 patients, 35 females and 25 males (ratio of 1.4:1). The age range was 17-87 years, mean 67.7 + 14.36 years. Only 3 (5%) patients were under 40 years, the remaining clustered predominantly in the 60-80 year age group. The mean age of females (59 + 13.84) was significantly lower than that of males (67.44 + 14) (p = 0.03). There was an almost equal distribution between the oral soft tissue and the jawbones (48.3% and 51.7%, respectively). The five most common organs from which metastases were distributed to the oral cavity and jawbones combined were kidney (20%), breast (15%), cutaneous (predominately melanoma, 13%), lung (11.7%) and soft tissue-sarcomas (8.3%). For comparison, Israel National Cancer Registry 2013 reported that the most frequent malignancies were breast (25.8%), colorectal cancer (16.3%), lung (12%) and prostate (10%). Malignant melanoma was 6th (5.4%), kidney malignancy was only 9th in frequency (4.2%). Although the gingiva and jawbones were the most frequent locations, some cases presented in unusual locations, (mandibular vestibule, lower lip, posterior dorsal tongue), without any specific clinical feature to suggest metastasis. CONCLUSIONS: The most frequent primary origins for oral metastasis do not correspond to the relative frequency of the primary tumors in the population, indicating that metastatic spread is not a random process. Although the majority of metastasis involves the gingiva and jawbones, any other oral mucosal location might be involved. Thus, in adult/older patients, metastasis from a distant site should be included in the differential diagnosis of oral masses at any oral location, whether the existence of a primary tumor is reported or not.