Clinicopathological characteristics and diagnostic accuracy of BRAF mutations in ameloblastoma: A Bayesian network analysis.

OBJECTIVE: This Bayesian network meta-analysis was performed to analyze the associations between clinicopathological characteristics and BRAF mutations in ameloblastoma (AM) patients and to evaluate the diagnostic accuracy. MATERIALS AND METHODS: Four electronic databases were searched from 2010 to 2024. The search terms used were specific to BRAF and AM. Observational studies or randomized controlled trials were considered eligible. The incidence of BRAF mutation and corresponding clinicopathological features in AM patients were subjected to Bayesian network analyses and diagnostic accuracy evaluation. RESULTS: A total of 937 AM patients from 20 studies were included. The pooled prevalence of BRAF mutations in AM patients was 72%. According to the Bayesian network analysis, BRAF mutations are more likely to occur in younger (odds ratio [OR], 2.3; credible interval [CrI]: 1.2-4.5), mandible site (OR, 3.6; 95% CrI: 2.7-5.2), and unicystic (OR, 1.6; 95% CrI: 1.1-2.4) AM patients. Similarly, higher diagnostic accuracy was found in the younger, mandible, and unicystic AM groups. CONCLUSIONS: The incidence, risk, and diagnostic accuracy of BRAF mutation in AM were greater in younger patients, those with mandible involvement, and those with unicystic AM than in patients with other clinicopathological features. In addition, there was a strong concordance in the diagnostic accuracy between molecular tests and immunohistochemical analysis.

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.

Calcifying Odontogenic Cyst Demonstrates Recurrent WNT Pathway Mutations and So-Called Adenoid Ameloblastoma-Like Histology: Evidence Supporting Its Classification as a Neoplasm.

Calcifying odontogenic cyst (COC), once called calcifying cystic odontogenic tumor, is classified under the category of odontogenic cysts. However, the proliferative capacity of the lesional epithelium and consistent nuclear ß-catenin expression raise questions about its current classification. This study aimed to determine whether COC would be better classified as a neoplasm in the histologic and molecular context. Eleven odontogenic lesions diagnosed as COC or calcifying cystic odontogenic tumor were included in this study. The growth patterns of the lesional epithelium were analyzed histologically in all cases. ß-catenin immunohistochemistry and molecular profiling using Sanger sequencing and whole-exome sequencing were performed in 10 cases. Of the 11 cases studied, histologic features reminiscent of so-called adenoid ameloblastoma were observed in 72.7% (8/11), and small islands of clear cells extended into the wall in 36.4% (4/11). Intraluminal and/or mural epithelial proliferation was found in 72.7% of the cases (8/11). Nuclear ß-catenin expression was observed focally in all 10 cases studied, mainly highlighting epithelial cells forming morules and adjacent to dentinoid. CTNNB1 hotspot mutations were detected in 60.0% of the cases (6/10). All the remaining cases had frameshift mutations in tumor-suppressor genes involved in the WNT pathway, including APC and NEDD4L. Recurrent WNT pathway mutations leading to nuclear translocation of ß-catenin and distinct epithelial growth patterns found in COC are the neoplastic features shared by its solid counterpart, dentinogenic ghost cell tumor, supporting its classification as a tumor rather than a cyst.

Frequency of BRAF V600E immunoexpression in ameloblastomas: a multi-institutional analysis of 86 cases in Latin America and comprehensive review of the literature.

BACKGROUND: Paracoccidioidomycosis (PCM) is the leading cause of death among systemic mycoses in Brazil. On the other hand, oral squamous cell carcinoma (OSCC) is the most prevalent malignant neoplasm of the mouth. Both lesions rarely affect the tongue dorsum and may share similar clinical characteristics. This study aimed to retrieve cases of single oral ulcers diagnosed as PCM or OSCC. MATERIAL AND METHODS: A cross-sectional retrospective study was conducted. All patients who had a single ulcer on dorsum of the tongue and confirmed diagnosis of PCM or OSCC were evaluated. RESULTS: A total of 9 patients (5 women and 4 men) were evaluated, 5 patients had OSCCs (mean age = 69,8 years old), and 4 patients PCM (mean age = 51 years old). Most of the lesions were infiltrated and indurated in the palpation exam. Duration ranged from 1 to 12 months (mean time of 5.2 months and 4.7 months for OSCC and PCM, respectively). OSCC was the main clinical diagnosis hypothesis. CONCLUSIONS: Although uncommon, PCM and OSCC should be considered as a differential diagnosis hypothesis in infiltrated ulcers on the tongue dorsum. Incisional biopsy is mandatory to confirm the diagnosis and indicate the appropriate treatment.

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/ß-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.

It was not possible to detect BRAF V600E mutation in circulating cell-free DNA from patients with ameloblastoma: A diagnostic accuracy study.

BACKGROUND: The objective of this study is to evaluate the diagnostic accuracy of plasma-based liquid biopsy for the detection of the BRAF V600E mutation in circulating cell-free DNA from patients with ameloblastoma. METHODS: This is a prospective diagnostic accuracy study conducted based on the Standards for Reporting Diagnostic Accuracy recommendations. The index test was the plasma-based liquid biopsy, whereas the reference standard was the conventional tissue biopsy. The target condition was the detection of BRAF V600E mutation. The study population consisted of individuals with ameloblastoma recruited from three tertiary hospitals from Brazil. A negative control group composed of three individuals with confirmed wild-type BRAF lesions were included. The participants underwent plasma circulating cell-free DNA and tumor tissue DNA isolation, and both were submitted to using competitive allele-specific TaqMan™ real-time polymerase chain reaction technology mutation detection assays. Sensitivity and specificity measures and positive and negative predictive values were calculated. RESULTS: Twelve patients with conventional ameloblastoma were included. BRAF V600E mutation was detected in 11/12 (91.66%) ameloblastoma tissue samples. However, the mutation was not detected in any of the plasma-based liquid biopsy circulating cell-free DNA samples in both ameloblastomas and negative control group. The sensitivity and specificity of plasma-based liquid biopsy for the detection of the BRAF V600E mutation in circulating cell-free DNA was 0.0 and 1.0, respectively. The agreement between index test and reference standard results was 26.66%. CONCLUSION: Plasma-based liquid biopsy does not seem to be an accurate method for the detection of the BRAF V600E mutation in circulating circulating cell-free DNA from patients with ameloblastoma, regardless of tumor size, anatomic location, recurrence status, and other clinicopathological features.

Exploiting BRAF mutations in the therapeutic approach towards oral and maxillofacial tumors.

Oral and maxillofacial tumors pose a significant clinical challenge due to their tendency to recur, despite advancements in surgical removal techniques. The jaw's intricate structure further complicates treatments and affects patient quality of life. Consequently, emphasis has shifted towards pharmacological interventions, to potentially reduce invasive surgical procedures. One promising approach targets BRAF mutations, specifically the common V600E mutation. BRAF, a critical protein kinase, regulates cell growth and differentiation via the RAS-RAF-MEK-ERK-MAP kinase pathway. A specific nucleotide change at position 1799, swapping Thymine (T) for Adenine (A), results in the V600E mutation, causing unchecked cell growth. This mutation is common in certain oral and maxillofacial tumors like ameloblastoma. A recent neoadjuvant therapy targeting BRAF, involving the use of dabrafenib and trametinib, has showcased a promising, safe, and effective strategy for organ preservation in the treatment of mandibular ameloblastoma. This convergence of molecular insights and targeted therapies holds the key to managing BRAF-mutated oral and maxillofacial tumors effectively, promising improved patient outcomes.

BRAF p.V600E Mutational Status Does Not Correlate with Biological Behavior in Conventional Ameloblastomas: A Disease-Free Survival Analysis.

BACKGROUND: Dysregulation of the MAPK pathway appears to exert a pivotal role in the pathogenesis of ameloblastomas, since BRAF p.V600E has been reported in over 65% of the tumors. Therefore, the purpose of this study was to investigate whether the BRAF p.V600E is related to biological behavior and disease-free survival in patients with conventional ameloblastomas. METHODS: This is a retrospective cohort study based on the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) recommendations. The study population consisted of individuals treated for conventional ameloblastomas. Clinical, imaging, histomorphological, immunohistochemical (Ki67 and CD138/syndecan-1), and molecular BRAF p.V600E mutation analyses were performed. Bivariate statistical analysis was performed through chi-square and Fisher's exact tests. Kaplan-Meier analysis with log-rank test and Cox proportional hazards regression were used to identify predictors of disease-free survival, with a significance level of 5%. RESULTS: Forty-one individuals were included, with a male-to-female ratio of 1.15:1. BRAF p.V600E mutation was identified in 75.6% of the tumors. No association between the BRAF mutational status and other clinical, imaging, histomorphological, and immunohistochemical variables was observed. Only the initial treatment modality was significantly associated with a better prognosis in univariate (p = 0.008) and multivariate (p = 0.030) analyses, with a hazard ratio of 9.60 (95%IC = 1.24-73.89), favoring radical treatment. CONCLUSION: BRAF p.V600E mutation emerges as a prevalent molecular aberration in ameloblastomas. Nevertheless, it does not seem to significantly affect the tumor proliferative activity, CD138/syndecan-1-mediated cell adhesion, or disease-free survival outcomes.

Single-cell transcriptomics reveals cell atlas and identifies cycling tumor cells responsible for recurrence in ameloblastoma.

Ameloblastoma is a benign tumor characterized by locally invasive phenotypes, leading to facial bone destruction and a high recurrence rate. However, the mechanisms governing tumor initiation and recurrence are poorly understood. Here, we uncovered cellular landscapes and mechanisms that underlie tumor recurrence in ameloblastoma at single-cell resolution. Our results revealed that ameloblastoma exhibits five tumor subpopulations varying with respect to immune response (IR), bone remodeling (BR), tooth development (TD), epithelial development (ED), and cell cycle (CC) signatures. Of note, we found that CC ameloblastoma cells were endowed with stemness and contributed to tumor recurrence, which was dominated by the EZH2-mediated program. Targeting EZH2 effectively eliminated CC ameloblastoma cells and inhibited tumor growth in ameloblastoma patient-derived organoids. These data described the tumor subpopulation and clarified the identity, function, and regulatory mechanism of CC ameloblastoma cells, providing a potential therapeutic target for ameloblastoma.

METTL1 facilitates ameloblastoma invasive growth via MAPK signaling pathway.

OBJECTIVES: Ameloblastoma (AM), a common odontogenic epithelial tumor, exhibits aggressive growth due to incomplete encapsulation within the jawbone. Postoperative recurrence is a significant concern, closely associated with its invasive nature. We investigate the role of tRNA N-7 methylguanosine (m7G) modification mediated by Methyltransferase-like 1 (METTL1) in AM's invasive growth and prognosis. MATERIALS AND METHODS: METTL1 expression was analyzed in diverse cell lines and clinical AM tissues. Its association with postoperative AM recurrence was examined. Functional experiments included METTL1 gene silencing using shRNA in hTERT-AM cells, assessing cell proliferation, migration, and invasion. Xenograft tumor model was constructed to investigate tumor growth. Molecular mechanisms behind METTL1's role in AM invasiveness were elucidated using Ribosome nascent-chain complex-bound mRNA sequencing (RNC-seq) and experimental analysis. RESULTS: High METTL1 expression was significantly associated with postoperative recurrence in AM. The inhibition of AM development following METTL1 knockdown has been corroborated by experiments conducted both in vitro and in vivo. Analysis of RNC-seq data revealed that downregulated genes were predominantly enriched in the mitogen-activated protein kinase (MAPK) signaling pathway, suggesting that METTL1 may promote AM's invasive growth through the MAPK signaling pathway. CONCLUSION: Our study elucidates the functional role of METTL1 in AM's invasive development and prognosis. High METTL1 expression is linked to postoperative recurrence, and METTL1 appears to promote AM invasiveness through the MAPK signaling pathway. These findings contribute to a better understanding of AM pathogenesis and may guide future therapeutic strategies.

Association of MDM2 Overexpression in Ameloblastomas with MDM2 Amplification and BRAFV600E Expression.

Ameloblastoma is a rare tumor but represents the most common odontogenic neoplasm. It is localized in the jaws and, although it is a benign, slow-growing tumor, it has an aggressive local behavior and high recurrence rate. Therefore, alternative treatment options or complementary to surgery have been evaluated, with the most promising one among them being a targeted therapy with the v-Raf murine sarcoma viral oncogene homologue B (BRAF), as in ameloblastoma the activating mutation V600E in BRAF is common. Studies in other tumors have shown that the synchronous inhibition of BRAF and human murine double minute 2 homologue (MDM2 or HDM2) protein is more effective than BRAF monotherapy, particularly in the presence of wild type p53 (WTp53). To investigate the MDM2 protein expression and gene amplification in ameloblastoma, in association with BRAFV600E and p53 expression. Forty-four cases of ameloblastoma fixed in 10% buffered formalin and embedded in paraffin were examined for MDM2 overexpression and BRAFV600E and p53 expression by immunohistochemistry, and for MDM2 ploidy with fluorescence in situ hybridization. Sixteen of forty-four (36.36%) cases of ameloblastoma showed MDM2 overexpression. Seven of sixteen MDM2-positive ameloblastomas (43.75%) were BRAFV600E positive and fifteen of sixteen MDM2-positive ameloblastomas (93.75%) were p53 negative. All MDM2 overexpressing tumors did not show copy number alterations for MDM2. Overexpression of MDM2 in ameloblastomas is not associated with MDM2 amplification, but most probably with MAPK activation and WTp53 expression. Further verification of those findings could form the basis for the use of MDM2 expression as a marker of MAPK activation in ameloblastomas and the trial of dual BRAF/MDM2 inhibition in the management of MDM2-overexpressing/BRAFV600E-positive/WTp53 ameloblastomas.

DNA content and clinicopathological features aid in distinguishing ameloblastic carcinoma from ameloblastoma.

BACKGROUND: Ameloblastoma and ameloblastic carcinoma are epithelial odontogenic tumors that can be morphologically similar. In the present study, we evaluated the DNA content and Ki-67 index in the two tumors. METHODS: The paraffin blocks of the tumors were selected to obtain sections for the immunohistochemical reactions and preparation of the cell suspension for acquisition in a flow cytometer. The Random Forest package of the R software was used to verify the contribution of each variable to classify lesions into ameloblastoma or ameloblastic carcinoma. RESULTS: Thirty-two ameloblastoma and five ameloblastic carcinoma were included in the study. In our sample, we did not find statistically significant differences in Ki-67 labeling rates. A higher fraction of cells in 2c (G1) was correlated with the diagnosis of ameloblastoma, whereas higher rates of 5c-exceeding rate (5cER) were correlated with ameloblastic carcinoma. The Random Forest model highlighted histopathological findings and parameters of DNA ploidy study as important features for distinguishing ameloblastoma from ameloblastic carcinoma. CONCLUSION: Our findings suggest that the parameters of the DNA ploidy study can be ancillary tools in the classification of ameloblastoma and ameloblastic carcinoma.

Transformation of an odontogenic keratocyst into a solid variant of odontogenic keratocyst/keratoameloblastoma during long­term follow­up: A case report.

Keratoameloblastoma (KA) and solid variant of odontogenic keratocyst (SOKC) are rare odontogenic lesions, and their relationship and differences are unclear. The present study described a case that started as an odontogenic keratocyst (OKC) and transformed to SOKC/KA upon recurrence. Briefly, a 26­year­old man presented with swelling in the right cheek and was referred to the Department of Oral and Maxillofacial surgery, Hiroshima University Hospital (Hiroshima, Japan). At the initial visit, unicystic bone permeation was observed extending from the right canine to the molar, maxillary sinus and nasal cavity. After the biopsy, the patient underwent excisional surgery and was diagnosed with OKC. Thereafter, the lesion recurred six times over a period of 13 years and showed different histopathological features from those of the primary lesion, all consisting of numerous cysts with keratinization, which were diagnosed as SOKC/KA. The Ki­67 positivity rate was ~10%, which was higher than that of the primary lesion, but there was no atypia. Genetic analysis of the recurrent lesion revealed mutations in adenomatous polyposis coli and Kirsten rat sarcoma viral oncogene homolog. This case originated from OKC, and the morphological features of OKC and KA were mixed upon recurrence, supporting the commonality and association between the two. However, multiple mutations different from those of OKC and ameloblastoma were detected, suggesting an association of SOKC/KA with increased proliferative activity and a high recurrence rate.

Comparison of diagnostic methods for detection of BRAFV600E mutation in ameloblastoma.

BACKGROUND: Ameloblastoma is an aggressively growing, highly recurrent odontogenic jaw tumor. Its association with BRAFV600E mutation is an indication for BRAFV00E-inhibitor therapy The study objective was to identify a sensitive low-cost test for BRAFV600E-positive ameloblastoma. We hypothesized that immunohistochemical staining of formalin-fixed paraffin-embedded tissues for BRAFV600E mutation is a low-cost surrogate for BRAFV600E gene sequencing when laboratory resources are inadequate for molecular testing. METHODS: Tissues from 40 ameloblastoma samples were retrieved from either formalin-fixed paraffin-embedded blocks, RNAlater™ stabilization solution or samples inadvertently pre-fixed in formalin before transfer to RNAlater™. BRAFV600E mutation was assessed by Direct Sanger sequencing, Amplification Refractory Mutation System-PCR and immunohistochemistry (IHC). RESULTS: BRAFV600E mutation was detected by IHC, Amplification Refractory Mutation System-PCR and Direct Sanger sequencing in 93.33%, 52.5% and 30% of samples respectively. Considering Direct Sanger sequencing as standard BRAFV600E detection method, there was significant difference between the three detection methods (𝜒2 (2) = 31.34, p < 0.0001). Sensitivity and specificity of IHC were 0.8 (95% CI: 0.64-0.90) and 0.9 (95% CI: 0.75-0.99) respectively, while positive predictive value and negative predictive value (NPV) were 0.9 and 0.8 (Fischer's test, p < 0.0001) respectively. Sensitivity and specificity of Amplification Refractory Mutation System-PCR detection method were 0.7 (95% CI: 0.53-0.80) and 0.9 (95% CI = 0.67-0.98) respectively, while PPV and NPV were 0.9 and 0.6 respectively (Fischer's test, p < 0.0001). CONCLUSION: Low-cost and less vulnerability of IHC to tissue quality make it a viable surrogate test for BRAFV600E detection in ameloblastoma. Sequential dual IHC and molecular testing for BRAFV600E will reduce equivocal results that could exclude some patients from BRAFV600E-inhibitor therapies.

Resolution of PTHrP-Mediated Hypercalcemia Following Treatment with Dual BRAF/MEK Inhibition for BRAFV600E-Positive Metastatic Ameloblastoma.

Ameloblastoma is a rare odontogenic tumor which may be complicated by hypercalcemia in advanced disease. Tumoral parathyroid hormone-related peptide (PTHrP) production and local osteolysis from paracrine factors have been proposed as mechanisms. Mitogen-activated protein kinase (MAPK) inhibitors have been successfully used in ameloblastomas with BRAF V600E mutation to reduce symptoms and decrease tumor burden. Serum calcium has been observed to normalize following treatment with MAPK inhibitors; however, the response of PTHrP and markers of bone turnover has not been reported. We describe a case of a 55-year-old female with PTHrP-mediated hypercalcemia secondary to BRAF V600E-positive ameloblastoma with pulmonary metastases. Following treatment with dabrafenib and trametinib, the patient experienced the regression of pulmonary lesions and normalization of serum calcium, PTHrP, and markers of bone turnover. Tissue samples of ameloblastoma carrying BRAF V600E mutation are more likely to express PTHrP than tissue samples carrying wild-type BRAF. In our case, resolution of PTHrP-mediated hypercalcemia following initiation of BRAF/MEK inhibition provides additional evidence that the MAPK pathway contributes to PTHrP synthesis. It also raises the question of whether MAPK inhibitors would be effective in treating PTHrP-mediated hypercalcemia associated with other malignancies harboring BRAF V600E mutation.

Differential Profile of Primary and Recurrent Ameloblastomas Among Afro-descendants and Non-Afro-descendants-a Systematic Review.

Ameloblastoma is an aggressively growing jaw tumor with high recurrent properties. Reports on global and racial distribution of ameloblastoma are variable and inconclusive. The role of race and ethnicity on ameloblastoma growth characteristics, genetic mutational profile, and recurrence is also still unclear. The primary aim of this systematic review was to assess genetic, racial, and ethnic distribution of primary and recurrent ameloblastoma from published literature. The secondary aim was to assess potential correlations between ethnicity, genetic mutation, and disparities in ameloblastoma treatment outcomes in Afro-descendants and non-Afro-descendants. Twenty-three eligible articles were selected based on preferred reporting items for systematic review and meta-analysis (PRISMA), and a total of 169 ameloblastoma cases were evaluated. Data on patient demographics, ameloblastoma growth characteristics, and genetic status were collected for quantitative analysis. Among a total of 169 ameloblastoma cases, Afro-descendant patients had higher primary and recurrent ameloblastomas at 15.5% and 4.7% respectively compared to non-Afro-descendant at 10.7% and 1.8% respectively. Additionally, BRAF V600E was positively associated with 48.8% of all ameloblastomas and strong predilection for Afro-descendants. Despite the paucity of information on genetic profile of ameloblastomas in the Afro-descendant patient cohort, this ethnic group still accounted for 2.95% of all BRAF V600E-positive tumors. These suggest that Afro-descendants are understudied regarding ameloblastoma characteristics, genetic profile, and recurrence profile. Mutational analysis of ameloblastoma tumors in Afro-descendants should be promoted.

Neoadjuvant BRAF-targeted therapy for ameloblastoma of the mandible: an organ preservation approach.

BACKGROUND: Ameloblastoma is a rare odontogenic neoplasm frequently located in the mandible. Standard treatment involves radical bone resection and immediate reconstruction, causing functional, aesthetic, and psychological impairments. The BRAF V600E mutation is present in approximately 80% of mandible ameloblastomas, and BRAF inhibitors have demonstrated sustained responses in unresectable cases. METHODS: We identified ameloblastoma patients planned for ablative surgery and screened them for BRAF V600E mutation. Neoadjuvant BRAF inhibitors were offered to facilitate jaw preservation surgery. Retrospective data collection encompassed treatment regimens, tolerability, tumor response, and conversion to mandible preservation surgery. RESULTS: Between 2017 and 2022, a total of 11 patients received dabrafenib (n = 6) or dabrafenib with trametinib (n = 5). The median age was 19 (range = 10-83) years. Median treatment duration was 10 (range = 3-20) months. All (100%) patients achieved a radiological response. Ten (91%) patients successfully converted to mandible preservation surgery with residual tumor enucleation. One patient attained complete radiological response, and surgery was not performed. Among the 10 surgically treated patients, all exhibited a pathological response, with 4 achieving near complete response and 6 partial response. At a median follow-up of 14 (range = 7-37) months after surgery, 1 case of recurrence was observed. Grade 1-2 adverse effects were reported in 8 (73%) patients, with a single case of grade 3 (hepatitis). Dose modification was necessary for 3 patients, and 4 experienced treatment interruptions, while 1 patient permanently discontinued therapy. CONCLUSIONS: Neoadjuvant BRAF inhibition may offer a safe and effective strategy for organ preservation in mandible ameloblastoma treatment.

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.

Localization of beta catenin across the domain of odontogenic lesions: A systematic review.

BACKGROUND: CTNNB1 gene encodes beta catenin, a transcriptional activator of Wnt pathway involved in the pathogenesis of odontogenic lesions. Though located intramembranously, its translocation into cytoplasm and nucleus could trigger cell proliferation, inhibition of apoptosis, invasion and migration of the tumour cell. MATERIALS AND METHODS: Five electronic databases including MEDLINE by PubMed, Google scholar, Scopus, Trip, Cochrane library and EMBASE until 1 January 2023 without period restriction were thoroughly searched. Those articles that identified CTNNB1 mutation and beta catenin in odontogenic lesions were included for review. Risk of bias was analysed for each study using QUADAS 2 tool and Review Manager 5.3 was used to output its result. RESULTS: Thirty four published articles were included for data synthesis. A total of 1092 cases of odontogenic lesions were assessed for both CTNNB1 mutation and beta catenin expression. CTNNB1 mutation was observed in ameloblastoma, calcifying odontogenic cyst, calcifying cystic odontogenic tumour and all malignant odontogenic tumours. The beta catenin expression (nuclear and cytoplasmic) was maximum in odontogenic keratocyst and calcifying odontogenic cyst. The expression was variable in ameloblastomas, membranous in odontomas, calcifying cystic odontogenic tumour and nuclear in all malignant tumours. DISCUSSION AND CONCLUSION: High recurrence of odontogenic keratocyst and aggressiveness of solid ameloblastoma and malignant odontogenic tumours could be associated with the nuclear translocation of beta catenin. Disparity between CTNNB1 mutation and beta catenin expression within odontogenic lesions suggests alternate routes of beta catenin activation. The review results support the unique localisation of beta catenin as a helpful diagnostic factor in the pathogenesis of odontogenic lesions.