BRAFV600E mutation in the diagnosis of unicystic ameloblastoma

BRAF V600E mutation mediates invasive and growth features in ameloblastoma

OBJECTIVES

Ameloblastoma (AM), a locally aggressive tumor with extensive growth capacity, causes significant damage to the jaw and affects facial appearance. Although the high prevalence of BRAF V600E mutation in AM is known, its specific impacts on patients with AM remain unclear. Thus, the present study investigated the role of BRAF V600E mutation, thereby focusing on its impact on AM invasion and growth.

MATERIALS AND METHODS

Immunohistochemical analysis was used to compare BRAF V600E, MMP2, MMP9, and Ki-67 expressions in AM (n = 49), normal oral mucosa (NOM) (n = 10), and odontogenic keratocyst (OKC) (n = 15) tissues. AM was further classified according to the presence or absence of BRAF V600E. The relationship between BRAF V600E and invasion as well as growth was evaluated. In addition, correlation analysis was performed using immunohistochemistry and confirmed via double-labeling immunofluorescence. Finally, comparative analyses using mass spectrometry, immunohistochemistry, and immunofluorescence were performed to explore and identify underlying mechanisms.

RESULTS

AM exhibited a higher incidence of BRAF V600E mutation than NOM and OKC. BRAF V600E expression was positively correlated with the invasion-associated proteins MMP2 and MMP9 and the growth-related protein Ki-67. Proteomic data revealed that BRAF V600E primarily activates the MAPK signaling pathway in AM, particularly driving the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2).

CONCLUSIONS

In summary, the findings suggested that the BRAF V600E mutation enhances the invasion and growth abilities of AM via the MAPK/ERK signaling pathway. Thus, targeting BRAF V600E or the MAPK/ERK pathway may be a potential AM therapy.

Differences in BRAF V600E mutation between the epithelium and mesenchyme in classic ameloblastoma

PURPOSE

Laser capture microdissection (LCM) was used to pinpoint the mutated tissue in ameloblastoma and investigate whether B-Raf proto-oncogene, serine/threonine kinase (BRAF) mutation is the main pathogenic gene in classic ameloblastoma.

STUDY DESIGN

A total of 24 patients with ameloblastoma scheduled to undergo surgery between 2000 and 2024 were included in the study. LCM was used to isolate tumor cells. Oxford nanopore technology (ONT) was used to analyze the collected cells. GO and KEGG enrichment analyses were then performed on the 300 most highly expressed genes in the epithelial tissue and mesenchyme.

RESULTS

Mandibular follicular ameloblastoma showed BRAF V600E mutations in all epithelial cells but not in the mesenchyme. The mutation rate was significantly higher in mandibular ameloblastomas compared to the maxilla (P < .05). RNA-seq showed that traditional follicular ameloblastoma epithelium was enriched in "growth factor receptor binding" and "angiogenesis regulation," while the mesenchyme was enriched in "ECM receptor interaction." KEGG enrichment analysis showed differential gene expression, mainly in MAPK and PI3K-AKT pathways.

CONCLUSION

Classical follicular ameloblastoma shows the presence of BRAF V600E mutation in epithelial tissue, with a higher mutation rate in the mandible than in the maxilla. The signaling pathways of MAPK and PI3K may be significantly involved in epithelial signal transduction.

Function and Therapeutic Potential of Non-Coding RNA in Ameloblastoma

Ameloblastoma (AB) is a common odontogenic tumor that develops in the mouth. Despite its benign nature, AB exhibits significant invasiveness leading to tumor metastasis and high postoperative recurrence rates. Studies have shown a relationship between the occurrence and development of various tumors and non-coding RNA (ncRNA). NcRNA, transcribed from the genomes of mammals and other complex organisms, are often products of alternative splicing and processing into smaller products. MicroRNA (miRNA), circular RNA (circRNA), and long non-coding RNA (lncRNA) are the main types of ncRNA. NcRNA play increasingly significant roles in the pathogenesis of human cancers, regulating their occurrence and progression as oncogenes or tumor suppressors. They are involved in tumor development and progression through alternative splicing of pre-mRNA, transcriptional regulation, mRNA stability, protein translation, and chromatin remodeling and modification. The importance of ncRNA in AB has received significant attention in recent years. However, the biological functions and mechanisms of ncRNA in AB remain largely unknown. In this review, we not only explore the functions and roles of ncRNA in AB, but also describe and envision their potential functional roles as biomarkers in AB diagnosis. In particular, we highlight the potential of miR-29a as a molecular marker for diagnosis and therapy. As promising novel therapeutic targets, the biological functions of ncRNA need further study, which is indispensable.

Molecular pathogenesis of ameloblastoma

Ameloblastoma (AM) is a benign, although aggressive, epithelial odontogenic tumour originating from tooth-forming tissues or remnants. Its aetiopathogenesis remains unclear; however, molecular analysis techniques have allowed researchers to progress in understanding its genetic basis. The high frequency of BRAF p.V600E as a main driver mutation in AM is well established; nevertheless, it is insufficient to explain its tumourigenesis. In this review, we aimed to integrate the current knowledge about the biology of AM and to describe the main genetic alterations reported, focusing on the findings of large-scale sequencing and gene expression profiling techniques. Current evidence shows that besides BRAF mutation and activation of the MAPK pathway, alterations in Hedgehog and Wnt/β-catenin pathway-related genes are also involved in AM pathogenesis. Recently, a tumour suppressor gene, KMT2D, has been reported as mutated by different research groups. The biological impact of these mutations in the pathogenesis of AM has yet to be elucidated. Further studies are needed to clarify the impact of these findings in the identification of novel biomarkers that could be useful for diagnosing, classifying, and molecular targeting this neoplasm.

Does BRAF mutation status and related clinicopathological factors affect the recurrence rate of ameloblastoma? A systematic review, meta-analysis and metaregression

OBJECTIVES

This review aims to analyse the recurrence rate in BRAFv600e+ and BRAFv600e- ameloblastomas and explore its association with clinicopathological variables.

METHODS

A comprehensive search was conducted using databases including PubMed, Embase, Cochrane Central Register of Controlled Trials, Clinicaltrials.gov, Google Scholar and grey literature, without any limitation on start date or language up to 20 June 2023. A random effect meta-analysis was conducted and Metaregression analyses were performed based on available clinicopathological factors.

RESULTS

Fifteen studies met the criteria for meta-analysis of outcomes. There was no significant difference in overall recurrence rates between the two groups (risk difference = 0.001, p-value = 0.987). Increasing male:female ratio in the BRAFv600e+ group was associated with a lower reported recurrence, suggesting a higher recurrence rate in females. The odds of having mandibular lesion were four times higher in BRAFv600e+ cases compared to BRAFv600e- cases (confidence interval: 2.121-7.870, p < 0.001, I2  = 28.37%).

CONCLUSION

Within the BRAFv600e+ group, females showed a higher reported recurrence rate. This specific clinical group may benefit from BRAFv600e mutation investigation and potential upscaled surgical treatment and additional BRAF inhibitor therapy, which needs validation in future studies.

The Role of BRAF Inhibitors in the Management of Ameloblastoma: A Literature Review

Ameloblastoma is one of the most prevalent but enigmatic benign odontogenic tumors of the jaw, accounting for approximately 10% of all maxillary and mandibular tumors. This neoplasia is distinguished by exhibiting several clinical and histological variants along with several mutations that affect its behavior. The ameloblastoma treatment plan is determined by the tumor's size, anatomical location, histologic variant, and anatomical involvement. On chromosome 7, there is a proto-oncogene called BRAF. When BRAF is mutated, it becomes an oncogene and continuously produces proteins like MEK and ERK, members of mitogen-activated protein kinase (MAPK). In the signaling pathway, these proteins activate transcription factor inside the nucleus that helps in cell division and growth. Numerous neoplasms have been linked to more than 40 BRAF mutations. The most common one is BRAF proto-oncogene serine/threonine kinase (BRAF) V600E, whose treatment has been linked to a positive outcome. BRAF inhibitors like vemurafenib, dabrafenib, and sorafenib have shown excellent results, especially in metastatic ameloblastoma. BRAF, particularly in the case of metastatic ameloblastoma, inhibitors such as vemurafenib, dabrafenib, and sorafenib, has demonstrated outstanding results. Targeted therapies have been employed as adjuvant therapies to enhance cosmetic outcomes, even though no reports of serial cases demonstrate their effectiveness in ameloblastomas. In the treatment of ameloblastomas, the identification of BRAF V600E and additional mutations as the prime targeted therapies has proven to be a significant breakthrough where surgical treatment was contraindicated. In this article, we review the presence of BRAF V600E mutations, their inhibitors, and targeted therapies in ameloblastoma.

Differential expression of PEA3 in odontogenic cysts and tumors

BACKGROUND

PEA3 transcription factor has been identified as a downstream target of the MAPK and PI3K pathways, and PEA3 overexpression has been observed in a variety of tumor types. We aimed to evaluate PEA3 expression in odontogenic cysts and tumors and compare the expression among odontogenic lesions. In addition, the correlations between PEA3 expression and clinicopathological characteristics of conventional ameloblastoma and unicystic ameloblastoma were investigated.

METHODS

This study was performed on 165 samples of odontogenic cysts and tumors including 20 dentigerous cysts, 20 odontogenic keratocysts, 16 adenomatoid odontogenic tumors, 5 ameloblastic fibromas, 45 unicystic ameloblastomas, and 59 conventional ameloblastomas. The sections were immunohistochemically stained with mouse monoclonal anti-PEA3 antibody and PEA3 expression was evaluated as the immunoreactive score.

RESULTS

PEA3 expression was absent in all dentigerous cysts (DCs) and odontogenic keratocysts, while all adenomatoid odontogenic tumors showed either no (75%) or low (25%) expression of PEA3. Most of the ameloblastic fibromas (60%) displayed no PEA3 expression. A high expression of PEA3 was observed in a substantial number of unicystic ameloblastomas (48.9%) and conventional ameloblastomas (49.2%) in our study. PEA3 expression in DCs, odontogenic keratocysts and adenomatoid odontogenic tumors were significantly different from that in conventional ameloblastomas and that in unicystic ameloblastomas (p < 0.05). The expression of PEA3 was significantly different in the age groups of unicystic ameloblastomas and histological subtypes of conventional ameloblastomas (p < 0.05).

CONCLUSION

PEA3 overexpression is predominant in unicystic ameloblastomas and conventional ameloblastomas compared to other odontogenic lesions, indicating a pivotal role of PEA3 as a downstream effector of MAPK pathway in these two odontogenic lesions.

Does BRAF V600E mutation affect recurrence rate of ameloblastomas? Systematic review and meta-analysis

OBJECTIVE

The objective of this systematic review with meta-analysis was to critically evaluate the available data on the association of the BRAF V600E mutation and recurrence rate of ameloblastomas.

MATERIALS AND METHODS

This systematic review was registered in Prospero (CRD42020183645) and performed based on the PRISMA statement. A comprehensive search in PubMed, Web of Science, Scopus and Cochrane Library databases was performed in order to answer the question "Does BRAF V600E mutation affect recurrence rate of ameloblastomas?" Methodological quality and risk of bias of the selected studies were assessed with JBI Critical Appraise Tool. Meta-analysis of quantitative data was conducted with RevMan 5.3 and Jamovi 2.3.

RESULTS

The initial search identified 302 articles, and 21 met the inclusion criteria. A total of 855 subjects with ameloblastoma were included in the analysis. The pooled measures for frequency of BRAF V600E mutation was 65.30% (95% CI: 0.56-0.75; p < .001; I2  = 90.85%; τ = 0.205; p < .001), and the pooled recurrence rate was 25.30% (95% CI: 0.19-0.31; p < .001; I2  = 79.44%; τ = 0.118; p < .001). No differences in recurrence rate were observed between the BRAF V600E and wild type BRAF ameloblastomas, with a pooled Odds Ratio of 0.93 (95% CI: 0.56-1.54; p = .78; I2  = 31%; p = .09).

CONCLUSIONS

BRAF V600E mutation is a frequent event in ameloblastomas, but does not increase nor reduce its recurrence rate, and thus have a limited value in predicting its prognosis.

Machine learning-based radiomics for predicting BRAF-V600E mutations in ameloblastoma

Background

Ameloblastoma is a locally invasive and aggressive epithelial odontogenic neoplasm. The BRAF-V600E gene mutation is a prevalent genetic alteration found in this tumor and is considered to have a crucial role in its pathogenesis. The objective of this study is to develop and validate a radiomics-based machine learning method for the identification of BRAF-V600E gene mutations in ameloblastoma patients.

Methods

In this retrospective study, data from 103 patients diagnosed with ameloblastoma who underwent BRAF-V600E mutation testing were collected. Of these patients, 72 were included in the training cohort, while 31 were included in the validation cohort. To address class imbalance, synthetic minority over-sampling technique (SMOTE) is applied in our study. Radiomics features were extracted from preprocessed CT images, and the most relevant features, including both radiomics and clinical data, were selected for analysis. Machine learning methods were utilized to construct models. The performance of these models in distinguishing between patients with and without BRAF-V600E gene mutations was evaluated using the receiver operating characteristic (ROC) curve.

Results

When the analysis was based on radiomics signature, Random Forest performed better than the others, with the area under the ROC curve (AUC) of 0.87 (95%CI, 0.68-1.00). The performance of XGBoost model is slightly lower than that of Random Forest, and its AUC is 0.83 (95% CI, 0.60-1.00). The nomogram evident that among younger women, the affected region primarily lies within the mandible, and patients with larger tumor diameters exhibit a heightened risk. Additionally, patients with higher radiomics signature scores are more susceptible to the BRAF-V600E gene mutations.

Conclusions

Our study presents a comprehensive radiomics-based machine learning model using five different methods to accurately detect BRAF-V600E gene mutations in patients diagnosed with ameloblastoma. The Random Forest model's high predictive performance, with AUC of 0.87, demonstrates its potential for facilitating a convenient and cost-effective way of identifying patients with the mutation without the need for invasive tumor sampling for molecular testing. This non-invasive approach has the potential to guide preoperative or postoperative drug treatment for affected individuals, thereby improving outcomes.

Cystic Lesions of the Jaws: The Top 10 Differential Diagnoses to Ponder

BACKGROUND

Cystic lesions of the gnathic bones present challenges in differential diagnosis. This category includes a smorgasbord of odontogenic and non-odontogenic entities that may be reactive or neoplastic in nature. While most cystic jaw lesions are benign, variability in biologic behavior makes distinction between these entities absolutely crucial.

METHODS

Review.

RESULTS

Two clinical cases are presented in parallel and are followed by an illustrated discussion of the ten most likely differential diagnoses that should be considered when confronted with a cystic jaw lesion. Strong emphasis is placed on the histologic differences between these entities, empowering readers to diagnose them with confidence. Perhaps even more importantly, the more common diagnostic pitfalls in gnathic pathology are discussed, recognizing that a definitive diagnosis cannot be rendered in every situation. The histologic diagnoses for the two clinical cases are finally revealed.

CONCLUSION

Cystic lesions of the maxilla and mandible may be odontogenic or non-odontogenic. The most common cystic lesions are the reactive periapical cyst, and the dentigerous cyst (which is developmental in nature). It is important to note that cystic neoplasms also occur in the jaws, and that the presence of inflammation may obscure the diagnostic histologic features of lesions like odontogenic keratocyst and unicystic ameloblastoma. Ancillary testing is of limited diagnostic value in most scenarios. However, both clinical and radiographic information (such as the location, size, duration, associated symptoms, and morphology of the lesion in its natural habitat) are significantly useful.

The molecular basis of odontogenic cysts and tumours

The advances in molecular technologies have allowed a better understanding of the molecular basis of odontogenic cysts and tumours. PTCH1 mutations have been reported in a high proportion of odontogenic keratocyst. BRAF p.V600E are recurrent in ameloblastoma and KRAS p.G12V/R in adenomatoid odontogenic tumour, dysregulating the MAPK/ERK pathway. Notably, BRAF p.V600E is also detected in ameloblastic carcinoma, but at a lower frequency than in its benign counterpart ameloblastoma. Recently, adenoid ameloblastoma has been shown to be BRAF wild-type and to harbour CTNNB1 (β-catenin gene) mutations, further suggesting that it is not an ameloblastoma subtype. CTNNB1 mutations also occur in other ghost-cell-containing tumours, including calcifying odontogenic cysts, dentinogenic ghost cell tumours and odontogenic carcinoma with dentinoid, but the link between CTNNB1 mutations and ghost cell formation in these lesions remains unclear. Regarding mixed tumours, BRAF p.V600E has been reported in a subset of ameloblastic fibromas, ameloblastic-fibrodentinomas and fibro-odontomas, in addition to ameloblastic fibrosarcoma. Such mutation-positivity in a subset of samples can be helpful in differentiating some of these lesions from odontoma, which is BRAF-wild-type. Recently, FOS rearrangements have been reported in cementoblastoma, supporting its relationship with osteoblastoma. Collectively, the identification of recurrent mutations in these aforementioned lesions has helped to clarify their molecular basis and to better understand the interrelationships between some tumours, but none of these genetic abnormalities is diagnostic. Since the functional effect of pathogenic mutations is context and tissue-dependent, a clear role for the reported mutations in odontogenic cysts and tumours in their pathogenesis remains to be elucidated.

Factors affecting the accuracy of anti-BRAF V600E immunohistochemistry results in ameloblastomas

BACKGROUND

There are still some controversies about the results of anti-BRAF V600E-specific antibody immunohistochemistry in ameloblastomas. This study aimed to examine the accuracy of V600E-specific antibody immunohistochemistry in detection of BRAF V600E mutation in ameloblastoma tissue sections of different ages.

METHODS

The BRAF V600E status of 64 ameloblastoma specimens was assessed using both Sanger sequencing and V600E-specific antibody immunohistochemistry, and the sensitivity, specificity, positive predictive value, and negative predictive value were calculated. The difference in V600E-specific antibody immunohistochemistry staining intensity among the three groups of ameloblastoma tissue blocks of different ages was evaluated by chi-square test. The consistency between V600E-specific antibody immunohistochemistry and DNA sequencing results and the V600E-specific antibody immunohistochemistry staining intensity of 15 paired newly-cut and 3-month storage sections of the same 15 ameloblastomas were also compared.

RESULTS

For detection of BRAF V600E mutation, the V600E-specific antibody immunohistochemistry had high sensitivity (98.21% 55/56), specificity (87.5% 7/8), positive predictive value (98.21% 55/56), and negative predictive value (87.5% 7/8). Heterogeneity of the staining intensity was observed in the same tissue section, but all or none expression pattern was noticed in the solid tumor nests. The storage time of paraffin tissue blocks ranging from 2 to 14 years did not affect the V600E-specific antibody-positive staining intensity. However, the three-month storage sections showed a significant diminishment of V600E-specific antibody-positive staining signals.

CONCLUSIONS

The BRAF V600E-specific antibody immunohistochemistry is suitable for routine detection of BRAF V600E mutation in ameloblastomas. The all or none expression pattern suggests the BRAF V600E mutation may be an early event in the pathogenesis of ameloblastoma.

BRAF V600E Mutation in Ameloblastoma: A Systematic Review and Meta-Analysis

The discovery that ameloblastoma has a high mutation incidence of BRAF V600E may enable a better investigation of pathophysiology. However, there is inconsistent evidence regarding this mutation occurrence and its association with clinical information. This systematic review and meta-analysis aim to pool the overall mutation prevalence of BRAF V600E in reported ameloblastoma cases and to determine its association with patient demographic and clinicopathological features. Following the PRISMA guidelines, a comprehensive article search was conducted through four databases (Scopus, Google Scholar, PubMed, and Web of Science). Seventeen articles between 2014 and 2022 met the inclusion criteria with 833 ameloblastoma cases. For each included study, the significance of BRAF V600E on the outcome parameters was determined using odd ratios and 95% confidence intervals. Meta-analysis prevalence of BRAF V600E in ameloblastoma was 70.49%, and a significant meta-analysis association was reported for those younger than 54 years old and in the mandible. On the contrary, other factors, such as sex, histological variants, and recurrence, were insignificant. As a result of the significant outcome of BRAF V600E mutation in ameloblastoma pathogenesis, targeted therapy formulation can be developed with this handful of evidence.

Identification of BRAF V600E mutation in odontogenic tumors by high-performance MALDI-TOF analysis

Odontogenic tumors are rare lesions with unknown etiopathogenesis. Most of them are benign, but local aggressiveness, infiltrative potential, and high recurrence rate characterize some entities. The MAP-kinase pathway activation can represent a primary critical event in odontogenic tumorigenesis. Especially, the BRAF V600E mutation has been involved in 80–90% of ameloblastic lesions, offering a biological rationale for developing new targeted therapies. The study aims to evaluate the BRAF V600E mutation in odontogenic lesions, comparing three different detection methods and focusing on the Sequenom MassARRAY System. 81 surgical samples of odontogenic lesions were subjected to immunohistochemical analysis, Sanger Sequencing, and Matrix-Assisted Laser Desorption/Ionization-Time of Flight mass spectrometry (Sequenom). The BRAF V600E mutation was revealed only in ameloblastoma samples. Moreover, the presence of BRAF V600E was significantly associated with the mandibular site (ρ = 0.627; P value <0.001) and the unicystic histotype (ρ = 0.299, P value <0.001). However, any significant difference of 10-years disease-free survival time was not revealed. Finally, Sequenom showed to be a 100% sensitive and 98.1% specific, suggesting its high-performance diagnostic accuracy. These results suggest the MAP-kinase pathway could contribute to ameloblastic tumorigenesis. Moreover, they could indicate the anatomical specificity of the driving mutations of mandibular ameloblastomas, providing a biological rational for developing new targeted therapies. Finally, the high diagnostic accuracy of Sequenom was confirmed.

Diagnostic accuracy of immunohistochemistry compared with molecular tests for detection of BRAF V600E mutation in ameloblastomas: systematic review and meta-analysis

OBJECTIVE

The objective of this systematic review with meta-analysis was to critically evaluate the available data on sensitivity and specificity of IHC compared with molecular tests in the detection of BRAF V600E mutation in ameloblastomas.

MATERIALS AND METHODS

This systematic review was performed based on the PRISMA statement and registered in Prospero (CRD42021259117). PubMed, Web of Science, Scopus and Cochrane Library databases were searched for observational studies to answer the question "What is the diagnostic accuracy of immunohistochemistry compared with molecular tests for the diagnosis of BRAF V600E mutation in ameloblastomas?". Methodological quality and risk of bias assessment of the selected studies were based on the QUADAS-2. Meta-analysis based on hierarchical SROC curve model and summary measures for sensitivity and specificity were computed.

RESULTS

A total of 226 records were found, but only 05 articles met the inclusion criteria, with 277 FFPE specimens of ameloblastoma included in the quantitative analysis. The sensitivity of the IHC compared to molecular tests ranged from 0.71 to 1.00, while all of the included studies showed perfect specificity (1.00). Pooled measures for sensitivity and specificity were 0.95 [95% CI 0.89, 1.00] and 1.00 [95% CI 0.95, 1.00], respectively. The Diagnostic Odds Ratio was 4.05 and the AUC for SROC curve was calculated as 0.979.

CONCLUSIONS

BRAF V600E-specific IHC using VE1 antibody showed extremely high sensitivity and specificity when compared with molecular tests in the detection of the mutation in ameloblastomas.

The Molecular Pathology of Odontogenic Tumors: Expanding the Spectrum of MAPK Pathway Driven Tumors

Odontogenic tumors comprise a heterogeneous group of lesions that arise from the odontogenic apparatus and their remnants. Although the etiopathogenesis of most odontogenic tumors remains unclear, there have been some advances, recently, in the understanding of the genetic basis of specific odontogenic tumors. The mitogen-activated protein kinases/extracellular signal-regulated kinases (MAPK/ERK) pathway is intimately involved in the regulation of important cellular functions, and it is commonly deregulated in several human neoplasms. Molecular analysis performed by different techniques, including direct sequencing, next-generation sequencing, and allele-specific qPCR, have uncovered mutations in genes related to the oncogenic MAPK/ERK signaling pathway in odontogenic tumors. Genetic mutations in this pathway genes have been reported in epithelial and mixed odontogenic tumors, in addition to odontogenic carcinomas and sarcomas. Notably, B-Raf proto-oncogene serine/threonine kinase (BRAF) and KRAS proto-oncogene GTPase (KRAS) pathogenic mutations have been reported in a high proportion of ameloblastomas and adenomatoid odontogenic tumors, respectively. In line with the reports about other neoplasms that harbor a malignant counterpart, the frequency of BRAF p.V600E mutation is higher in ameloblastoma (64% in conventional, 81% in unicystic, and 63% in peripheral) than in ameloblastic carcinoma (35%). The objective of this study was to review MAPK/ERK genetic mutations in benign and malignant odontogenic tumors. Additionally, such genetic alterations were discussed in the context of tumorigenesis, clinical behavior, classification, and future perspectives regarding therapeutic approaches.

Genetic Profile of Adenomatoid Odontogenic Tumor and Ameloblastoma. A Systematic Review

Purpose: To perform a comprehensive and systematic critical appraisal of the genetic alterations reported to be present in adenomatoid odontogenic tumor (AOT) compared to ameloblastoma (AM), to aid in the understanding in their development and different behavior.

Methods: An electronic search was conducted in PubMed, Scopus, and Web of Science during March 2021. Eligibility criteria included publications on humans which included genetic analysis of AOT or AM.

Results: A total of 43 articles reporting 59 AOTs and 680 AMs were included. Different genomic techniques were used, including whole-exome sequencing, direct sequencing, targeted next-generation sequencing panels and TaqMan allele-specific qPCR. Somatic mutations affecting KRAS were identified in 75.9% of all AOTs, mainly G12V; whereas a 71% of the AMs harbored BRAF mutations, mainly V600E.

Conclusions: The available genetic data reports that AOTs and AM harbor somatic mutations in well-known oncogenes, being KRAS G12V/R and BRAFV600E mutations the most common, respectively. The relatively high frequency of ameloblastoma compared to other odontogenic tumors, such as AOT, has facilitated the performance of different sequencing techniques, allowing the discovery of different mutational signatures. On the contrary, the low frequency of AOTs is an important limitation for this. The number of studies that have a assessed the genetic landscape of AOT is still very limited, not providing enough evidence to draw a conclusion regarding the relationship between the genomic alterations and its clinical behavior. Thus, the presence of other mutational signatures with clinical impact, co-occurring with background KRAS mutations or in wild-type KRAS cases, cannot be ruled out. Since BRAF and RAS are in the same MAPK pathway, it is interesting that ameloblastomas, frequently associated with BRAFV600E mutation have aggressive clinical behavior, but in contrast, AOTs, frequently associated with RAS mutations have indolent behavior. Functional studies might be required to solve this question.

Genetic Study of BRAF V600E and SMO L412F Mutations in Japanese Patients with Ameloblastoma

Background and aim: Ameloblastoma is a benign, intraosseous, progressively growing, epithelial, odontogenic neoplasm. BRAF and SMO mutations have been reported in ameloblastoma. In this study, we evaluated BRAF V600E and SMO L412F mutations; and assessed the relationship between BRAF V600E mutant expression and the clinicopathological features in Japanese patients with ameloblastoma. Methods: We examined 24 formalin-fixed paraffin-embedded samples. All specimens were from patients with mandibular ameloblastoma: 20 were conventional ameloblastoma and 4 were unicystic ameloblastoma. The BRAF V600E mutation was assessed by Sanger sequencing and immunohistochemistry, and the SMO L412F mutation was assessed only by Sanger sequencing. Results: Twenty of the 24 (83%) ameloblastoma samples carried the BRAF V600E mutation; 22 of the 24 (92%) samples were immunohistochemically positive for BRAF V600E. However, the SMO L412F mutation was not detected in any of them. The BRAF V600E mutation status did not correlate with the clinicopathological features, such as age, sex, location, method, recurrence, and subtype. Conclusion: BRAF inhibitors could be a potential treatment option for Japanese patients with ameloblastoma, harboring the BRAF V600E mutation.

Correlation of BRAF mutational status with clinical characteristics and survival outcomes of patients with ameloblastoma: the experience of 11 Italian centres

AIMS

Ameloblastoma is a rare odontogenic tumour with an aggressive local behaviour. Mutations in the mitogen-activated protein kinase pathway, namely BRAF V600E mutations, are a common finding. To date, there is no clear correlation between BRAF V600 mutation and clinical outcome.

METHODS

We retrospectively reviewed the medical records of patients who underwent surgery for ameloblastoma between May 1998 and June 2018, at 11 participating Italian centres. BRAF mutational status was evaluated by quantitative PCR/pyrosequencing. The primary end points were to determine BRAF mutational status in primitive and recurrent ameloblastoma, and to assess the relapse-free interval (RFI); the secondary end point was to investigate the correlation of BRAF mutational status with the clinical features of the tumour and survival outcomes.

RESULTS

Overall, 74 patients were included: 33 (44.5%) were BRAF wild type and 41 (55.4%) BRAF V600 mutated. BRAF V600 mutated ameloblastomas occurred more frequently in younger patients (p=0.0031), were located at the mandible (p=0.0009) and presented with unicystic variant. After a median follow-up of 60 months, 21 (28.3%) patients relapsed (30.3% and 26.8% in the BRAF wild type and BRAF mutated group, respectively). At univariable Cox models, none of the investigated variables, including microscopic margin involvement, was associated with RFI.

CONCLUSIONS

Local recurrence occurs in 30% of patients with ameloblastoma. BRAFV600 mutation is associated with younger age, mandibular localisation and with unicystic ameloblastoma. Neither BRAF mutation nor microscopically positive surgical margins were associated with RFI. Further studies are needed to elucidate outcomes of this rare disease according to clinical, histopathological and comprehensive molecular features.

BRAF p.V600E status in epithelial areas of ameloblastoma with different histological aspects: Implications to the clinical practice

BACKGROUND

BRAF p.V600E is reported in up to 80% of ameloblastomas. Despite the high frequency, the presence of this mutation in different histopathological areas of the tumour has not been investigated. This information has an important role in the use of BRAF p.V600E assessment as an auxiliary tool in the differential diagnosis between unicystic ameloblastoma and other odontogenic cystic lesions, especially when only incisional biopsies are available. Therefore, the purpose of the present study was to investigate BRAF p.V600E heterogeneity in unicystic ameloblastoma.

METHODS

Five cases of ameloblastoma and two dentigerous cysts were analysed. The regions exhibiting different microscopic characteristics were selected from each ameloblastoma case and manually dissected. TaqMan allele-specific qPCR or Sanger sequencing was performed to determine BRAF p.V600E status.

RESULTS

We screened the mutation in a small cohort of UA and no molecular heterogeneity was found. Four cases of ameloblastoma (80%) exhibited BRAF p.V600E in all different areas evaluated. One case did not harbour the mutation in any microscopic region analysed. The BRAF mutation was absent in the dentigerous cysts.

CONCLUSION

Ameloblastomas appear to exhibit a homogeneous profile regarding the BRAF p.V600E no matter what histological feature is observed under light microscopy, suggesting that this molecular test may contribute to establish the correct diagnosis in cases microscopically resembling other odontogenic lesions.

Analyses of odontogenic tumours: the most recent classification proposed by the World Health Organization (2017)

BACKGROUND

The fourth edition of the ''WHO Classification of Head and Neck Tumours'' was published in January 2017 and includes a classification of odontogenic tumours. This review aims to examine the changes made in this new classification in comparison with the previous classification of 2005.

MATERIAL AND METHODS

An electronic search was conducted in the PubMed, Scopus and Cochrane databases with the keywords "odontogenic tumor", "WHO classification" and "update". Studies published from January 2009 to April 2019 with a high level of scientific evidence were included, but studies not published in English, epidemiological studies and studies with a low level of evidence were excluded.

RESULTS

The initial search found 457 articles and after eliminating duplicates, 8 studies were selected for full-text assessment. After excluding 3 epidemiological studies, 5 articles were finally included. These studies were stratified by their level of scientific evidence using SORT criteria (Strength of Recommendation Taxonomy).

CONCLUSIONS

The new odontogenic tumour list has been simplified with the objective of improving its role as an international guide for diagnosis. Some changes have been possible thanks to the application of immunohistochemistry and molecular genetic techniques that allow better characterization of certain tumours. Further clinicopathological and molecular studies are needed so that this new classification can be consolidated and/or amended.

Discrepancy between immunohistochemistry and sequencing for BRAF V600E in odontogenic tumours: Comparative analysis of two VE1 antibodies

BACKGROUND

Although immunohistochemistry (IHC) along with molecular tests has been investigated in ameloblastoma for BRAF V600E detection, VE1 IHC has not been studied in odontogenic carcinomas (OCs) and benign mixed epithelial and mesenchymal odontogenic tumours (BMOTs). Here, we performed BRAF V600E mutation analysis, examined the expression pattern of VE1 IHC, and comparatively evaluated the performance of two VE1 antibodies in ameloblastomas, OCs and BMOTs.

METHODS

BRAF V600E detection was performed using Sanger sequencing in a total of 47 odontogenic tumours: 28 ameloblastomas, 6 OCs and 13 BMOTs. VE1 IHC was conducted using two different antibodies (IHC-A and IHC-V), and their performance was analysed by calculating the sensitivity and specificity compared with sequencing.

RESULTS

BRAF V600E mutations were identified in 24/28 (85.7%) ameloblastomas, 2/5 (40.0%) ameloblastic carcinomas (ACs), 3/7 (42.9%) ameloblastic fibromas and 1/2 (50.0%) ameloblastic fibro-odontomas. In the presence of the mutation, VE1 showed diffuse cytoplasmic staining in ameloblastomas and ACs, whereas all BMOTs were negative for VE1. IHC-A and IHC-V yielded a sensitivity of 76.7% and 60.0%, respectively, although both antibodies showed 100% specificity.

CONCLUSION

OCs and BMOTs have BRAF V600E mutations in common at lower frequencies than ameloblastoma. Diffuse VE1 cytoplasmic staining in AC suggests the utility of MAPK-targeted therapy as selectively applied in ameloblastoma, and consistent VE1 false-negative expression in BMOTs requires further investigation. Considering the high specificity but low sensitivity of VE1 IHC, molecular tests should be performed to determine the presence of BRAF V600E mutations in odontogenic tumours.

Ameloblastoma: A succinct review of the classification, genetic understanding and novel molecular targeted therapies

Ameloblastomas are benign but locally invasive neoplasms which may grow to massive proportions and cause significant morbidity. Although some types of ameloblastoma can be treated predictably with aggressive surgical treatment, recurrent ameloblastoma and metastasising ameloblastoma are still difficult to treat. Recent studies have identified recurrent somatic and activating mutations in the mitogen-activated protein kinase (MAPK) and sonic hedgehog (SHH) signalling pathways in ameloblastoma. This development provided a possibility that molecular targeted therapies can be used as neoadjuvant treatment. In this review, we provide a summary of the latest WHO classification of ameloblastoma, the current understanding of genetic mutations and novel molecular targeted therapies arising from the recent developments.

Frequency of BRAF V600E mutation in a group of Thai patients with ameloblastomas

OBJECTIVE

BRAF V600E mutation has recently been reported in a high proportion of ameloblastomas. This study was conducted to investigate the frequency of this mutation in ameloblastoma and unicystic ameloblastoma. The correlation between clinicopathologic data and BRAF V600E mutation was also analyzed.

STUDY DESIGN

A total of 51 archival samples of ameloblastomas and 22 cases of unicystic ameloblastomas were examined for BRAF V600E mutation by using anti-BRAF V600E (clone VE1) immunohistochemistry.

RESULTS

Positivity for anti-BRAF V600E antibody was detected in 72.5% (37 of 51) of ameloblastomas, but the mutation showed no significant correlation with the clinicopathologic parameters. With regard to unicystic ameloblastoma, 95.5% (21) of the 22 cases exhibited positive immunostaining for BRAF V600E, whereas only 1 case showed the mural subtype of wild-type BRAF.

CONCLUSIONS

A high frequency of BRAF V600E mutation was detected in a group of Thai patients with ameloblastomas, suggesting the future use of BRAF-targeted therapy in patients with BRAF-mutated ameloblastoma. However, no significant association between BRAF V600E mutation and the clinicopathologic characteristics of ameloblastomas was found in our study.

Ameloblastoma with mucous cells: A clinicopathological, BRAF mutation, and MAML2 rearrangement study

OBJECTIVES

To investigate the clinicopathological features, BRAF V600E mutation, and MAML2 rearrangement of ameloblastoma with mucous cell differentiation.

MATERIALS AND METHODS

Five cases of ameloblastoma with mucous cell differentiation were retrospectively studied. Clinicopathological features, BRAF V600E mutation, and MAML2 rearrangement were analyzed. Follow-up information was available for all cases.

RESULTS

Of five cases, two cases were male and three were female, aged 18-55 years. Four cases were located in the mandible and one case in the maxilla. Histologically, four of the five cases (80%) presented with cystic features and three of the five cases (60%) with varying degrees of squamous metaplasia. The mucous cells were located in the epithelial islands or the luminal aspect of the cystic cavities. The BRAF V600E mutation was found in three of five cases (60%). All the cases showed no MAML2 rearrangement. Two cases were recurrent lesions, and one case had a local recurrence during the follow-up.

CONCLUSIONS

Ameloblastoma with mucous cell differentiation is closely related to the cystic features, squamous metaplasia, and shows a high prevalence of BRAF V600E mutation. The absence of MAML2 rearrangement reveals that ameloblastoma with mucous cell differentiation and central mucoepidermoid carcinoma (MEC) are two distinct tumor entities.

A review of the molecular profile of benign and malignant odontogenic lesions

Odontogenic cysts and tumors are heterogeneous lesions, originating from elements or remnants of the odontogenic apparatus. Although the majority of these lesions are benign and never undergo malignant transformation, rare malignant tumors may arise de novo or from benign precursors. The molecular basis of these lesions is still poorly understood. This article summarizes and discusses studies using small, medium, and large-scale and/or "-omic" techniques to describe the molecular characteristics of benign and malignant odontogenic lesions and briefly debates strategies to increase the use of "-omic" and multi-omic approaches or integrative analyses in the research of these lesions. A comprehensive understanding of the molecular aspects of odontogenic lesions by using large-scale approaches will enable us to refine the classification of this heterogeneous group of disorders and provide more accurate biomarkers for precise diagnosis, prognosis, and development of molecular tools in the management of patients with these conditions.

Current concepts in ameloblastoma-targeted therapies in B-raf proto-oncogene serine/threonine kinase V600E mutation: Systematic review

BACKGROUND

Ameloblastomas are common benign epithelial odontogenic neoplasms that present an aggressive and unpredictable behavior that may modify treatment strategies. Different signaling pathways that participate in the progression of these tumors have been identified. B-raf proto-oncogene serine/threonine kinase (BRAF) is a protein involved in the behavior of ameloblastomas, and it is related to many cell mechanisms. BRAF gene mutations have been identified in ameloblastomas, of which the BRAF V600E (valine substituted by glutamic acid at amino acid 600) mutation has been the most common and can be present concomitantly with other mutations that may be involved in its behavior. Targeted therapies have been used as an alternative in the case of resistance or contraindications to conventional treatments.

AIM

To document the presence of BRAF V600E and additional mutations, their behavior, and targeted therapies in these tumors.

METHODS

An electronic literature search was conducted according to PRISMA guidelines in PubMed/MEDLINE, Cochrane, EMBASE, and SpringerLink using the terms “ameloblastomas”, “BRAF V600E”, “additional mutations”, and “targeted therapies”. Ameloblastomas were classified according to WHO guidelines. Inclusion criteria were articles in English, published not more than 10 years ago, and studies with laboratory works related to BRAF V600E. Articles were evaluated by two independent reviewers and retrieved for full-text evaluation. The EBLIP Critical Appraisal Checklist was used to evaluate the quality of the eligible studies. Descriptive statistical analysis was performed.

RESULTS

Two independent reviewers, with a substantial concordance indicated by a kappa coefficient of k = 0.76, evaluated a total of 19 articles that were included in this study. The analysis registered 521 conventional ameloblastomas (AM), 81 unicystic ameloblastomas (UA), 13 ameloblastic carcinomas (AC), three metastatic ameloblastomas (MA), and six peripheral ameloblastomas (PA), of which the histopathological type, anatomic location, laboratory tests, expression of BRAF mutation, and additional mutations were registered. The BRAF V600E mutation was found in 297 AM (57%), 63 UA (77.7%), 3 AC (23%), 1 MA (50%), and 5 PA (83.3%). Follicular type predominated with a total of 116 cases (40%), followed by plexiform type with 63 cases (22.1%). Furthermore, both types presented additional mutations, in which alterations in JAK3 P132T, SMARCB1, PIK3CA, CTNNB1, SMO, and BRAF G606E genes were found. Four case reports were found with targeted therapy to BRAF V600E.

CONCLUSION

The identification of BRAF V600E and additional mutations as an aid in targeted therapies has been a breakthrough in alternative treatments of ameloblastomas where surgical treatments are contraindicated.

An immunohistochemical and genetic study of BRAFV600E mutation in Japanese patients with ameloblastoma

Ameloblastoma is an odontogenic tumor of the jaw. It most frequently occurs in the mandible, and less often in the maxilla. Mandibular ameloblastoma harbors a BRAF mutation that causes a valine (V) to glutamic acid (E) substitution at codon 600 (BRAF^V600E ). We examined specimens from 32 Japanese patients to detect the prevalence of the BRAF^V600E mutation, and to evaluate the relationship between immunohistochemical (IHC) expression and genetic results, of BRAF^V600E+ ameloblastoma. Among the 32 cases, 22 (69%) were IHC positive for BRAF^V600E protein, and 10 (31%) were IHC negative; and polymerase chain reaction showed 16 of 21 tested cases (76%) carried the BRAF^V600E mutation. Our findings indicate that that samples that stain IHC positive for BRAF^V600E protein are more likely to carry the BRAF^V600E mutation. These results support assessments for BRAF mutations, and the use of BRAF inhibitors as targeted therapy for ameloblastoma in Japanese patients.

Immunoexpression of DNA base excision repair and nucleotide excision repair proteins in ameloblastomas, syndromic and non-syndromic odontogenic keratocysts and dentigerous cysts

OBJECTIVE

To evaluate the immunoexpression of DNA base excision repair (BER) [apurinic/apyrimidinic endonuclease 1 (APE-1), X-ray repair cross complementing 1 (XRCC-1)] and nucleotide excision repair (NER) [xeroderma pigmentosum complementation group (XPF)] proteins in benign epithelial odontogenic lesions with different biological behaviors.

DESIGN

Thirty solid ameloblastomas, 30 non-syndromic odontogenic keratocysts (NSOKCs), 29 syndromic odontogenic keratocysts (SKOCs), 30 dentigerous cysts (DCs) and 20 dental follicles (DFs) were evaluated quantitatively for APE-1, XRCC-1 and XPF through immunohistochemistry.

RESULTS

Nuclear expression of APE-1 was significantly higher in NSOKCs, SOKCs, and ameloblastomas in comparison to DCs (p < 0.001). Nuclear expression of XRCC-1 was higher in NSOKCs and SOKCs than in DCs (p < 0.05). At the nuclear level, XPF expression was higher in NSOKCs and SOKCs than in DCs and ameloblastomas (p < 0.05). A statistically significant higher expression of APE-1 (nuclear), XRCC-1 (nuclear), and XPF (nuclear and cytoplasmic) was found in all odontogenic lesion samples as compared to DFs (p < 0.05). For all lesions, there was a positive correlation between nuclear expression of APE-1 and XRCC-1 or XPF (p < 0.05).

CONCLUSIONS

Our results suggest a potential involvement of APE-1, XRCC-1 and XPF proteins in the pathogenesis of benign epithelial odontogenic lesions, especially in those with more aggressive biological behavior, such as ameloblastomas, NSOKCs, and SOKCs. We also showed that the expression of APE-1 was positively correlated with the nuclear expression of XRCC-1 and XPF, which may suggest an interaction between the BER and NER pathways in all odontogenic lesions studied herein.

Mutational Signatures in Mandibular Ameloblastoma Correlate with Smoking

Ameloblastoma is a rare tumor of odontogenic epithelium, the low incidence rate of which precludes statistical determination of its molecular characterizations. Despite recent genomic and transcriptomic profiling, the etiology of ameloblastomas remains poorly understood. Risk factors of ameloblastoma development are also largely unknown. Whole exome sequencing was performed on 11 mandibular ameloblastoma samples. We identified 2 convergent mutational signatures in ameloblastoma: 1) a signature found in multiple types of lung cancers with probable etiology of tobacco carcinogens (COSMIC signature 4) and 2) a signature present in gingivobuccal oral squamous cell carcinoma and correlated with tobacco-chewing habits (COSMIC signature 29). These mutational signatures highlight tobacco usage or related mutagens as one possible risk factor of ameloblastoma, since the association of BRAF mutations and smoking was demonstrated in multiple studies. In addition to BRAF hotspot mutations (V600E), we observed clear inter- and intratumor heterogeneities. Interestingly, prior to BRAF mutation, important genes regulating odontogenesis mutated (e.g., corepressor BCOR), possibly playing important roles in tumorigenesis. Furthermore, recurrent mutations in the CDC73 gene, the germline mutations of which predispose patients to the development of jaw tumors, were found in 2 patients, which may lead to recurrence if not targeted by therapeutic drugs. Our unbiased profiling of coding regions of ameloblastoma genomes provides insights to the possible etiology of mandibular ameloblastoma and highlights potential disease risk factors for screening and prevention, especially for Asian patients. Because of the limited sample size and incomplete habitual, dietary, and occupational data, a causal link between tobacco usage and ameloblastoma still requires further investigations.

Advancements in MAPK signaling pathways and MAPK-targeted therapies for ameloblastoma: A review

Numerous signal transduction pathways are closely associated with the occurrence, development, and prognosis of ameloblastoma (AM). Mitogen-activated protein kinase (MAPK) is a serine/threonine-specific protein kinase that transduces intracellular signals in critical cellular phenomena. A number of recent analyses have reported that the MAPK signaling pathway contributes significantly to AM. High-throughput DNA sequencing methods, such as next-generation sequencing using Illumina have yielded advancements in studies on MAPK signaling pathways and their association with AM; in particular, BRAF V600E is mediated by the activation of the Ras/Raf/MAPK pathway. This review discusses advancements in studies on MAPK signaling pathways and MAPK-targeted inhibitors or antibodies, along with the merits and demerits of MAPK-targeted therapies, finally followed by a discussion regarding more efficient potential MAPK-targeted therapies to treat AM with few side effects, thereby providing novel insights into targeted therapy for AM.

The Mutational Profile of Unicystic Ameloblastoma

BRAF V600E is the most common mutation in conventional ameloblastoma (AM) of the mandible. In contrast, maxillary AMs appear to harbor more frequently RAS, FGFR2, or SMO mutations. Unicystic ameloblastoma (UAM) is considered a less aggressive variant of ameloblastoma, amenable to more conservative treatment, and classified as a distinct entity. The aim of this study was to characterize the mutation profile of UAM ( n = 39) and to compare it to conventional AM ( n = 39). The associations between mutation status and recurrence probability were also analyzed. In the mandible, 94% of UAMs (29/31, including 8/8 luminal, 6/8 intraluminal, and 15/15 mural subtypes) and 74% of AMs (28/38) revealed BRAF V600E mutations. Among the BRAF wild-type cases, 1 UAM showed a missense SMO mutation (p.L412F), whereas 2 NRAS (p.Q61R), 2 HRAS (p.Q61R), and 2 FGFR2 (p.C383R) activating mutations were identified in AM. Of the 3 maxillary UAMs, only 1 revealed a BRAF V600E mutation. Taken together, our findings demonstrate high frequency of activating BRAF V600E mutations in both UAM and AM of the mandible. In maxillary UAMs, the BRAF V600E mutation prevalence appears to be lower as was shown for AM previously. It could therefore be argued that UAM and AM are part of the spectrum of the same disease. AMs without BRAF V600E mutations were associated with an increased rate of local recurrence ( P = 0.0003), which might indicate that routine mutation testing also has an impact on prognosis.

[Cystic lesions of the jaws]

Cystic lesions of the jaws comprise a spectrum of inflammatory, developmental and neoplastic changes that can clinically appear strikingly similar. Squamous cell metaplasia due to superinfection can further blur the histologic hallmarks of the individual lesions. In this article an overview of the most important differential diagnoses and the novelties of the latest World Health Organisation (WHO) classification on head and neck tumours released in early 2017 is provided. In contrast to the previous edition, odontogenic cysts have been re-introduced and several changes in terminology and taxonomy have been complemented.

Low frequency of BRAF V600E immunoexpression in mandibular ameloblastomas: An institutional study

Background:

Ameloblastoma is an uncommon, benign neoplasm of odontogenic epithelium commonly affecting the posterior mandible (almost 80%) particularly in the molar/ramus region, with occasional tumors involving the maxilla. Recently, there has been much interest generated after the reports of BRAF V600E mutations in ameloblastomas with a frequency of 46%–80% using both molecular as well as immunohistochemical (IHC) techniques. We sought to assess the presence of BRAF V600E expression in ameloblastomas in Indian patients and correlate the same with clinical behavior and histological variants by performing IHC analysis with anti-BRAF V600E antibody.

Materials and Methods:

Thirty formalin-fixed paraffin-embedded tissues of mandibular ameloblastomas were examined by anti-BRAF V600E antibody and correlated with clinicopathologic and histological parameters. Cytoplasmic staining of neoplastic epithelium was considered positive for BRAF V600E expression.

Statistical Analysis:

Data analysis was performed using Chi-square test and Student's t-test with statistical software IBM SPSS statistics 20.0.

Results:

BRAF V600E antibody showed positive expression only in 33.3% (10/30) cases. About 66.7% (4/6) recurrent cases and 63.6% (7/11) plexiform cases showed statistically significant association of P = 0.05 and P = 0.021, respectively, among cases with positive BRAF V600E immunoexpression.

Conclusion:

We report the lowest frequency (33.3%) of BRAF V600E immunoexpression in mandibular ameloblastomas in Indian population. However, a significant association of BRAF V600E-positive immunoexpression with recurrence and plexiform pattern could underline its role as a therapeutic marker for ameloblastoma.

Determination of BRAF V600E (VE1) protein expression and BRAF gene mutation status in codon 600 in borderline and low-grade ovarian cancers

Epithelial ovarian tumors are a group of morphologically and genetically heterogeneous neoplasms. Based on differences in clinical phenotype and genetic background, ovarian neoplasms are classified as low-grade and high-grade tumor. Borderline ovarian tumors represent approximately 10%-20% of all epithelial ovarian masses. Various histological subtypes of ovarian malignancies differ in terms of their risk factor profiles, precursor lesions, clinical course, patterns of spread, molecular genetics, response to conventional chemotherapy, and prognosis. The most frequent genetic aberrations found in low-grade serous ovarian carcinomas and serous borderline tumors, as well as in mucinous cancers, are mutations in BRAF and KRAS genes. The most commonly observed BRAF mutation is substitution of glutamic acid for valine in codon 600 (V600E) in exon 15. The primary aim of this study was to determine whether fully integrated, real-time polymerase chain reaction-based Idylla™ system may be useful in determination of BRAF gene mutation status in codon 600 in patients with borderline ovarian tumors and low-grade ovarian carcinomas. The study included tissue specimens from 42 patients with histopathologically verified ovarian masses, who were operated on at the Department of Obstetrics and Gynecology, Nicolaus Copernicus University Collegium Medicum in Bydgoszcz (Poland). Based on histopathological examination of surgical specimens, 35 lesions were classified as low-grade ovarian carcinomas, and 7 as borderline ovarian tumors. Specimens with expression of BRAF V600E (VE1) protein were tested for mutations in codon 600 of the BRAF gene, using an automated molecular diagnostics platform Idylla™. Cytoplasmic immunoexpression of BRAF V600E (VE1) protein was found in three specimens: serous superficial papilloma, serous papillary cystadenoma of borderline malignancy, and partially proliferative serous cystadenoma. All specimens with the expression of BRAF V600E (VE1) protein were tested positively for BRAF V600E/E2/D mutation. No statistically significant relationship (p > 0.05) was found between the presence of BRAF V600E mutation and the probability of 5-year survival. BRAF mutation testing with a rapid, fully integrated molecular diagnostics system Idylla™ may be also a powerful prognostic tool in subjects with newly diagnosed serous borderline tumors, identifying a subset of patients who are unlikely to progress.

Update from the 4th Edition of the World Health Organization Classification of Head and Neck Tumours: Odontogenic and Maxillofacial Bone Tumors

The 4th edition of the World Health Organization's Classification of Head and Neck Tumours was published in January of 2017. This article provides a summary of the changes to Chapter 4 Tumours of the oral cavity and mobile tongue and Chapter 8 Odontogenic and maxillofacial bone tumours. Odontogenic cysts which were eliminated from the 3rd 2005 edition were included in the 4th edition as well as other unique allied conditons of the jaws. Many new tumors published since 2005 have been included in the 2017 classification.

Rare copy number alterations and copy-neutral loss of heterozygosity revealed in ameloblastomas by high-density whole-genome microarray analysis

BACKGROUND

Ameloblastoma (unicystic, UA, or multicystic, MA) is a rare tumor associated with bone destruction and facial deformity. Its malignant counterpart is the ameloblastic carcinoma (AC). The BRAFV600E mutation is highly prevalent in all these tumors subtypes and cannot account for their different clinical behaviors.

METHODS

We assessed copy number alterations (CNAs) and copy-neutral loss of heterozygosity (cnLOH) in UA (n = 2), MA (n = 3), and AC (n = 1) using the CytoScan HD Array (Affymetrix) and the BRAFV600E status. RT-qPCR was applied in four selected genes (B4GALT1, BAG1, PKD1L2, and PPP2R5A) covered by rare alterations, also including three MA and four normal oral tissues.

RESULTS

Fifty-seven CNAs and cnLOH were observed in the ameloblastomas and six CNAs in the AC. Seven of the CNAs were rare (six in UA and one in MA), four of them encompassing genes (gains of 7q11.21, 1q32.3, and 9p21.1 and loss of 16q23.2). We found positive correlation between rare CNA gene dosage and the expression of B4GALT1, BAG1, PKD1L2, and PPP2R5A. The AC and 1 UA were BRAF wild-type; however, this UA showed rare genomic alterations encompassing genes associated with RAF/MAPK activation.

CONCLUSION

Ameloblastomas show rare CNAs and cnLOH, presenting a specific genomic profile with no overlapping of the rare alterations among UA, MA, and AC. These genomic changes might play a role in tumor evolution and in BRAFV600E-negative tumors.

Assessment of BRAF V600E (VE1) protein expression and BRAF gene mutation status in codon 600 in benign and malignant salivary gland neoplasms

BACKGROUND

The role of BRAF mutations in cancerogenesis has been demonstrated in several solid tumor types. However, in salivary gland tumors, this genetic alteration is very uncommon, and its role still remains unclear. Thus, the aim of this study was to analyze BRAF V600E (VE1) protein expression with BRAF mutation status in codon 600, in malignant and benign salivary gland tumors.

METHODS

Studies were performed on archived formalin-fixed paraffin-embedded tissue sections derived from 95 patients who underwent surgery for tumors of the salivary gland. Immunohistochemical staining (IHC) on tissue microarray slides was performed for evaluation of BRAF V600E (VE1) protein expression, and the automatic molecular diagnostics platform was used for the evaluation of mutations in codon 600 of BRAF gene.

RESULTS

IHC cytoplasmic expression of BRAF V600E (VE1) protein was found in two of 95 cases: one case of adenocarcinoma NOS (one of three; 33%) and one case of carcinoma ex pleomorphic adenoma (one of five; 20%). Although, in IHC studies, nuclear BRAF V600E (VE1) protein expression was found in 14 (15%) of the analyzed cases: nine of 28 (32%) cases of pleomorphic adenoma, three of five (60%) cases of ductal carcinoma, one of nine (11%) case of mucoepidermoid carcinoma, and in one of five (20%) case of carcinoma ex pleomorphic adenoma. All cases were negative for polymerase chain reaction PCR-based analyses of BRAF mutations in codon 600.

CONCLUSIONS

In studied salivary gland cancers, no PCR-based prove mutations of BRAF V600 were detected. Further molecular analyses are necessary to rapid molecular arrays for the identification of specific mutations, optimal for individualized targeted therapies.