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 (ß-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.

Cyclooxygenase-2 protein expression modulates cell proliferation and apoptosis in solid ameloblastoma and odontogenic keratocyst. An immunohistochemical study.

BACKGROUND: Cyclooxygenase-2 protein is a critically important mediator in inflammation that influences proliferation, apoptosis, angiogenesis and metastasis. Previous works showed a relationship between cyclooxygenase-2 and tumourigenesis in humans and animal models. In epithelial odontogenic tumours and cysts, increased cell proliferation and survival have been linked to its pathogenesis and tumour development. The aim of the present study was to analyse the immunohistochemical expression of cyclooxygenase-2 in solid ameloblastoma and odontogenic keratocyst and its association with proteins related to cell proliferation and apoptosis. METHODS: This study was conducted on 40 cases from the Pathological Anatomy Service, University of Chile. The cases were diagnosed as solid ameloblastoma (n = 21) and odontogenic keratocyst (n = 19) according to WHO 2017. Slides prepared from paraffin-embedded sections were immunohistochemically stained for cyclooxygenase-2, cyclin D1, Ki-67, p63 and Bcl-2. Statistical evaluation was performed by the Shapiro-Wilk test, ANOVA Mann-Whitney test and Spearman's correlation coefficient (p < 0.05). RESULTS: There were significant differences in the immunoexpression of cyclin D1, Ki-67 and Bcl-2 between solid ameloblastoma and odontogenic keratocyst. Likewise, there was a significant difference in the immunoexpression of p63 between follicular and plexiform histological types/subtypes of solid ameloblastoma. Lastly, there were statistical associations between cyclooxygenase-2 and Ki-67 for solid ameloblastoma and between cyclooxygenase-2 and p63 for odontogenic keratocyst. CONCLUSION: A high level of cyclooxygenase-2 is related to increased cell survival and proliferative activity in solid ameloblastoma and odontogenic keratocyst. This event might contribute to tumoural progression and local invasiveness in these lesions.

The Usefulness of a Facial Digital Biobank for Ameloblastoma Resection and Fracture Fixation - A Case Report.

Rationale: Ameloblastoma often requires complex facial treatments such as resection and reconstruction, which can be aided using three-dimensional resources towards improved surgical planning, reduction of surgical time, and customization. Patient Concerns: A 51-year-old patient, concerned about submandibular volumetric increase discovered performing imaging exams to install dental implants. Diagnosis and Treatment: Diagnosed with ameloblastoma, he underwent uneventful partial mandibular resection and placement of prebent mandibular reconstruction plate. Four months later, following a motorcycle accident, a deflection of the plate and mandibular fracture was observed. Using the initial prototyping, a new reconstruction plate was customized and surgically placed to reduce the mandibular fracture, with adequate titanium plate adaptation to the remaining bone and maintenance of aesthetic mandibular contour. Outcomes and Take-away Lessons: The current digital dentistry resources, such as computed tomography and intraoral scan, can be recovered and used as a backup of recorded anatomy anytime in future, providing a long-lasting facial digital biobank.

Management of Recurrence of Ameloblastoma and Odontogenic Keratocyst: A Cross-Sectional Study / Manejo de la recurrencia del ameloblastoma y keratoquiste odontogénico: Estudio de corte transversal

Abstract Objectives: Odontogenic keratocyst (OKC) and ameloblastoma are slowly growing and locally invasive tumors with high recurrence rate. The aim of this study was to investigate the clinicopathologic features of recurrent ameloblastoma and OKC cases, and evaluate outcomes of our treatments in terms of recurrence. Material and Methods: A total of 23 patients with confirmed recurrent ameloblastoma or OKC and treated in our clinic within eleven years period were reviewed retrospectively. Results: Eleven recurrent OKC cases and twelve recurrent ameloblastoma cases were included. Most recurrences occurred within five years after the initial treatment (69.6%). Enucleation had the highest recurrence rate among the first treatments (18/23). All recurrences were located in the mandible, with one exception (22/23). All recurrent OKCs were multilocular. Different histopathologic subtypes of ameloblastoma were seen in our study, follicular ameloblastoma was the most common (8/12). The mean diameter of the lesions was 4.3 cm (ranging from 2 cm to 7 cm). Statically significant relation was found between location and diameter of lesion and year of recurrence onset (p=0.004; p=0.026). We performed radical treatments in these cases (ten patients underwent marginal resections, and thirteen patients underwent segmental resection), and no recurrence was observed during the follow-up period. Conclusion: Previous inadequate surgical procedures were the most important cause of recurrence. Marginal or segmental resection with safety margins is the best method to treat recurrences of OKC or ameloblastoma cases.

Resumen Objetivo: Los keratoquistes odontogénicos (KQO) y ameloblastomas son tumores invasivos de lento crecimiento local con una alta tasa de recurrencia. El propósito de este estudio fue investigar las características clínico patológicas de los casos de ameloblastoma y KQO recurrentes y evaluar los resultados de tratamientos en término de recurrencia. Materiales y Métodos: Un total de 23 pacientes con casos confirmados de ameloblastomas o KQO recurrentes tratados en nuestra clínica en un período de once años fueron incluidos. Resultados: Once casos de KQO recurrentes y doce ameloblastomas recurrentes fueron incluidos. La mayoría de las recurrencias ocurrieron en los primeros 5 años posteriores al tratamiento inicial (69.6%). La enucleación mostró la tasa de recurrencia más alta entre los tratamientos iniciales (18/23). Todas las recurrencias se presentaron en la mandíbula excepto por un caso (22/23). Todos los KQO fueron multiloculares. Distintos subtipos histológicos del ameloblastoma fueron detectados en el estudio y el ameloblastoma folicular fue el más común (8/12). El diámetro promedio de las lesiones fue de 4.3cm en un rango de 2cm a 7cm. Una relación estadísticamente significativa se encontró entre la ubicación y el diámetro de la lesión y el tiempo de aparición de la recurrencia (p=0.004; p=0.026). Se realizaron tratamientos radicales en los siguientes casos, diez pacientes tuvieron resecciones marginales y trece pacientes resección segmental; no se observaron recurrencias en el período de seguimiento. Conclusión: Procedimientos previos inadecuados fueron la causa más relevante de recurrencia. Resección marginal o segmental con márgenes de seguridad son el mejor método para tratar casos de ameloblastoma y KQO recurrentes.

Teratocarcinoma-derived growth factor-1 (Cripto-1) is overexpressed in epithelial odontogenic lesions displaying more aggressive behaviour.

PURPOSE: Cripto-1 also known as teratoma-derived growth factor 1 (TDGF-1) belongs to the EGF-CFC family of growth factor-like molecules. Cripto-1 is involved with embryonic development and not expressed in adult tissue, but some tumours are accompanied by reactivation. METHODS: The aim of this study was to evaluate the immunohistochemical expression of Cripto-1 in most common odontogenic cysts and tumours. Thirty ameloblastomas, 30 keratocysts, 30 dentigerous cysts and two ameloblastic carcinomas were evaluated using the polymeric immunoperoxidase technique. Immunohistochemical expressions were analysed by the IRS (immunoreactive score). Statistical analyses were performed by the Kruskal-Wallis and Mann-Whitney tests (p ≤ 0.05). RESULTS: Age ranged from 9 to 75 years old, with a prevalence of females (n = 49/53.3%). The mandible was the most affected anatomical site (n = 69/75.0%). Cripto-1 immunoexpression was observed in all ameloblastoma, keratocyst and ameloblastic carcinoma cases, although nine dentigerous cyst cases (30%) were negative. Expression scores were higher in ameloblastoma, keratocyst and ameloblastic carcinoma cases (median ranging from 8 to 11) when compared with dentigerous cyst cases (median of 2), with a statistically significant difference (p < 0.001). CONCLUSIONS: Cripto-1 is critically important in the progression of several tumours since it is related to significant cell survival and differentiation pathways. The high expression of Cripto-1 in more aggressive odontogenic lesions suggests that this molecule may be involved in the activation of important pathways related to the etiopathogenesis of these lesions.

Can non-collagenous proteins be employed for the differential diagnosis among fibrous dysplasia, cemento-osseous dysplasia and cemento-ossifying fibroma?

Differential diagnosis among fibrous dysplasias, cemento-ossifying fibromas and cemento-osseous dysplasias is difficult, since there is considerable overlap of histologic features, but also extremely important, since they differ greatly in etiology, clinical behaviour, prognosis and terapeuthic approach. There is no data about the use of immunohistochemistry, a viable and accessible technique, for this purpose. The objective of this study was to investigate, comparatively, the immunohistochemical expression of major non-collagenous proteins (osteonectin [ON], osteopontin [OP], bone sialoprotein [BSP] and osteocalcin [OC]) of mineralized tissue extracellular matrix in 22 cases of fibrous dysplasias, 16 of cemento-ossifying fibromas and 16 of cemento-osseous dysplasias. ON maintained the same expression profile in all cases; the staining for OP was negative in fusiform cells producing cementoid globules and weak, as well as heterogeneous, in high mineralized matrixes; there was negativity for BSP in cementoid globules and in the fusiform cells that produce them, differently from the strong positive expression found in the majority of bone trabeculae and their peripheral cuboidal osteoblasts; and finally, the immuno-reactivity for OC was weak, except in cuboidal osteoblasts and osteocytes. We can conclude that the nature of mineralized structure and the cellular phenotype are much more responsible for variability in immunohistochemical profile than the type of lesion (fibrous dysplasias, cemento-ossifying fibromas and cemento-osseous dysplasias) which makes difficult, at least for a while, the use of these proteins with diagnosis purpose.

Patient-derived xenografts of a case of ameloblastic fibrodentinoma.

OBJECTIVES: The establishment of animal models of xenotransplantation can contribute to the elucidation of the molecular pathogenesis of ameloblastic fibrodentinomas (AFD) and it also provides an opportunity for drug tests. We aimed to evaluate the possibility of AFD tumour growth in a patient-derived xenograft (PDX) model. In addition, we characterized the human tumour and the PDXs. MATERIALS AND METHODS: A sample of a recurrent AFD was obtained and two fragments were contralaterally implanted subcutaneously in an 8-week old female NUDE mouse. After 250 days, the PDXs were removed and submitted to histopathological and molecular analysis. Immunohistochemical reactions for Ki67 and the phosphorylated form of ERK1/2 were carried out in both, PDXs and human tumour, and the presence of BRAFV600E was assessed. RESULTS: From day 135 onwards, the PDXs presented a growth peak and remained stable until day 250. Histopathologically, the PDXs presented the same features of the patient's tumour. Tumour cells exhibited Ki67 and pERK1/2 immunoexpression in the patient's tumour and PDX. The AFD was wild-type for BRAFV600E. CONCLUSION: The PDX model recapitulated well the human tumour after a long implantation time, representing a possible model to study the AFD and other odontogenic tumours pathobiology.

Calcifying epithelial odontogenic tumours: Collaborative study of 32 cases and review of literature.

OBJECTIVES: To analyse the occurrence of calcifying epithelial odontogenic tumours (CEOT) based on biopsy records from different Brazilian geographic regions and to contrast the data with a review of the literature. MATERIALS AND METHODS: A 2-step study was conducted. Step 1 consisted of a collaborative study of biopsies obtained from 1953 to 2017 at six Brazilian oral and maxillofacial pathology centres. Evaluation of 86,268 biopsy records was performed. Demographic and histopathological diagnosis data were assessed. In Step 2, a review of the literature of case reports and cases series of CEOT identified across five electronic databases was conducted. RESULTS: In the collaborative study, 32 cases of CEOT were evaluated. This figure represented 0.03% of the oral and maxillofacial lesions and 1.7% of all odontogenic tumours across the centres. Women in the fourth decade of life were more affected. CEOT occurred more in the mandible than in the maxilla (ratio 1.9:1). The review of the literature showed that Asian individuals were more affected by this neoplasm. CONCLUSIONS: Useful knowledge on the epidemiology, treatment and follow-up of CEOT has been provided. Demographic data and clinical features of the cases presented in this collaborative study were quite similar to those of studies reported worldwide.

Immunohistochemical analysis of BRAF V600E mutation in ameloblastomas.

OBJECTIVE: This study aimed to investigate the presence of BRAF V600E mutation in mandible ameloblastomas by correlating clinical and imaging data on the cases studied. METHODS: Eighty-four cases diagnosed as mandibular ameloblastoma were selected for analysis. The specimens were submitted to immunohistochemistry for detection of BRAF V600E mutated protein. Clinical-pathological data such as age, gender, tumour size, mandibular location, radiographic aspects, histological type and sub-type, and tumour status were collected. The clinical-pathological parameters were categorised and analysed according to BRAF V600E detection. RESULTS: Of the 84 patients, 78.6% (66 cases) demonstrated positivity for anti-BRAF V600E antibody, whereas 18 were negative (21.4%). The correlation between BRAF expression and variables showed statistical significances for mandibular location (P = 0.0353) and tumour size (P = 0.008), whereas no statistical significance was observed for gender, age, radiographic aspect, histological pattern, histological sub-type and tumour status. Multivariate logistic regression revealed a significant risk for BRAF positivity in tumours with posterior mandibular location (OR = 7.23, P = 0.0451) and size > 4 cm (OR = 7.29, P = 0.0150). CONCLUSION: BRAF V600E mutation is common in mandibular ameloblastomas, especially in cases of tumours larger than 4 cm and in the posterior region of the mandible. In addition, this mutation can occur regardless of histological type of the tumour, age, gender, radiographic aspect and tumour status. CLINICAL SIGNIFICANCE: The association between clinical-pathologic features and BRAF V600E mutation in ameloblastomas may provide directions for the treatment of this neoplasia. The use of BRAF inhibitors for targeted therapy could lead to an establishment of an alternative compared to the resective surgery.

Bringing benign ectomesenchymal odontogenic tumours to the lab: An in vitro study using an organotypic culture model.

BACKGROUND: Benign neoplasms exhibit most of the cellular phenomena considered hallmarks of cancer, except the capacity to metastasize. Thus, the elucidation of the mechanisms associated with the progression of benign neoplasms may complement and clarify the mechanisms involved in carcinogenesis. Benign odontogenic tumours often result in facial deformities and morbidities, and have complex pathogenesis, mainly due to the diversity of interactions between the odontogenic epithelium and the ectomesenchyme. Primary cell culture of such tumours is not only difficult to be established and maintained, but also tumour cells lose characteristic cellular morphology. Considering gene expression, growth, migration, proliferation and cellular morphology are controlled by cell-cell interactions and cell-extracellular matrix interactions, cell culture in 3D substrates has gained space as a way to overcome some of the limitations of traditional monolayer cell culture systems. METHODS: In this study, fragments obtained from mesenchymal odontogenic tumours were cultured in type I collagen scaffolds. Invasion tests were performed in these models, as well as phenotypic characterization of the cultured tumours. RESULTS: The results obtained for the odontogenic myxoma and the cemento-ossifying fibroma demonstrate a good reproduction of the growth pattern of these tumours under ex vivo conditions. Microscopic evaluation showed maintenance of cell viability in the explants for more than 30 days, without the presence of necrosis. CONCLUSION: This is the first study involving long-term 3D primary cultures of benign odontogenic tumours, which is expected to support complex approaches to cell and molecular biology, and to serve as an experimental model for testing molecular therapies.

Peripheral Developing Odontoma or Peripheral Ameloblastic Fibro-Odontoma Erupting to Oral Cavity Case Report / Odontoma en Desarrollo Periférico o Fibro-Odontoma Ameloblástico Periférico Eruptando a Cavidad Oral Reporte de Caso

ABSTRACT: The appearance of mixed odontogenic tumors into the oral cavity is a rare event. It is considered that some mixed tumors are only a stage in the complete development of a hamartomatous formation such as ameloblastic fibroodontoma and odontoma. Both pathologies share in common cellular elements which at one point makes them indistinguishable from each other. We present the case of a 21 year old patient who showed a mandibular growth whose histological elements present characteristics of both pathologies. The treatment was surgical excision of the lesion. There were no complications or recurrences to periodic reevaluation.

RESUMEN: La aparición de tumores odontogénicos mixtos en la cavidad oral es un evento raro. Se considera que algunos tumores mixtos son solo una etapa en el desarrollo completo de una formación hamartomatosa como el fibro-odontoma ameloblástico y odontoma. Ambas patologías comparten elementos celulares comunes que en un punto los hacen indistinguibles entre sí. Presentamos el caso de un paciente de 21 años que mostró un crecimiento mandibular cuyos elementos histológicos presentan características de ambas patologías. El tratamiento fue la escisión quirúrgica de la lesión. No hubo complicaciones o recurrencias a la reevaluación periódica.

BRAF-V600E expression correlates with ameloblastoma aggressiveness.

AIMS: The aim of this study was to investigate whether the expression of BRAF-V600E determines an aggressive clinical and molecular presentation of ameloblastoma. METHODS AND RESULTS: Ninety-three cases of solid ameloblastomas were arranged in a 1.0-mm tissue microarray (TMA) block. Immunohistochemistry against a large panel of cytokeratins (CK), epidermal growth factor receptor (EGFR), parathyroid hormone-related peptide (PTHrP), syndecan-1, Ki67, p53 and BRAF-V600E were performed. Clinicopathological parameters, including sex, age, tumour size, tumour duration, tumour location, treatment, recurrences, radiographic pattern, vestibular/lingual and basal cortical plates disruption and follow-up data, were obtained from patients' medical records. Immunoexpression of BRAF-V600E was investigated in 73 cases that remained available in TMA sections. Our results indicated that 46.6% (34 cases) demonstrated cytoplasm positivity (six weak and 28 strong positivity). BRAF-V600E expression was associated significantly with the expression of CK8 (P = 0.00077), CK16 (P = 0.05), PTHrP (P = 0.0082) and p53 (P = 0.0087). Additionally, a significant association was seen with the presence of recurrences (P = 0.0008), multilocular radiographic appearance (P = 0.044) and disruption of basal bone cortical (P = 0.05). Univariate analysis showed that BRAF-positive cases (P = 0.001), EGFR-negative/weak positive cases (P = 0.03) and multilocular tumours (P = 0.04) had a significantly lower disease-free survival rate, but these parameters were not considered independent prognostic factors in the multivariate analysis (P > 0.05). CONCLUSIONS: Our findings suggest an association of BRAF-V600E with parameters of a more aggressive behaviour of ameloblastoma, supporting the future use of BRAF inhibitors for targeted therapy of this neoplasm.

Immunoexpression of tumour necrosis factor-α, interleukin-1α and interleukin-10 on odontogenic cysts and tumours.

AIM: To analyse the immunoreactivity of IL-1α, TNF-α and IL-10 in odontogenic cysts and tumours and to investigate possible associations with established biological behaviours of these different lesions. METHODOLOGY: Immunohistochemical expression of anti-IL-1α, anti-TNF-α and anti-IL-10 antibodies was assessed on epithelium and mesenchyme of 20 radicular cysts (RCs), 20 residual cysts (RECs), 20 dentigerous cysts (DCs), 18 solid ameloblastomas (SAs), 20 keratocystic odontogenic tumours (KCOTs) and 15 dental follicles (DFs). Comparative analysis of data was performed using the nonparametric Wilcoxon signed-rank test and Kruskal-Wallis's test. RESULTS: Significantly greater expression of IL-1α in the epithelium was noted in RC, KCOT and SA (P = 0.01), whilst IL-10 and TNF-α was in the epithelium of RC, DC and KCOT (P < 0.01). In the mesenchyme, significantly greater immunopositivity was observed for IL-1α, IL-10 and TNF-α in KCOT, DC and RC (P < 0.01). In epithelial and mesenchymal tissues, there were a significant number of cases of RC and DC with IL-1α < IL-10 ratio (P < 0.01), whilst SA and KCOT showed IL-1α > IL-10 (P < 0.01). There was a significantly greater percentage of DF, DC and KCOT with TNF-α > IL10 ratio (P < 0.01). CONCLUSION: These results suggest involvement of the proteins in the pathogenesis of odontogenic cysts and tumours, with emphasis on the highest immunoreactivity of osteolysis stimulating factors in tumours with aggressive biological behaviour, such as SA and KCOT.

Cementoblastoma benigno: relato de caso / Benign Cementoblastoma: Case Report

O cementoblastoma benigno ou cementoma verdadeiro é uma neoplasia odontogênica benigna. Acredita-se que essa lesão é a única neoplasia verdadeira do cemento. Ela apresenta incidência entre 1 e 6,2% dentre os tumores odontogênicos, o que vem a tornála rara. Sendo assim, o objetivo do presente trabalho foi relatar o caso clínico de uma paciente com diagnóstico de cementoblastoma benigno, enfatizando as peculiaridades desse tumor, a importância do diagnóstico correto e o estabelecimento de um tratamento adequado, bem como ressaltar a importância da proservação do caso.

Benign cementoblastoma or true cementoma is a benign odontogenic tumour. It is believed that this lesion presents the unique true cementum neoplasm. It is a rare lesion comprising 1 to 6,2% of odontogenic tumours. Therefore, the objective of this study was to report the case of a patient diagnosed with benign cementoblastoma, emphasizing the peculiarities of this tumor, the importance of correct diagnosis and appropriate treatment setting, as well as underscoring the importance of proactive observation.

Immunohistochemical biomarkers in ameloblastomas.

Ameloblastoma is an aggressive odontogenic tumour, which is locally invasive and highly recurrent. Studies show that ameloblastoma is a benign odontogenic neoplasia, being relatively rare and occasionally presenting behaviour of malignant lesions. In addition to these particularities, the histological diagnosis of ameloblastoma can be challenging when the tumour shows high rates of mitosis, absence of nuclear pleomorphism, basilar hyperplasia and neural invasion. In order to help in the diagnosis, prognosis and treatment of this neoplasia, some immunohistochemical markers were shown to be associated with tumoural epithelium. The identification of these markers as well as of their association with clinical signs can be useful to elaborate more efficient treatment strategies and to control this pathology, including improvement of the quality of life of patients affected by this neoplasia. This article aims to review some markers associated with specific molecular pathways, bone remodelling, cell proliferation, apoptosis, cell signalling and tumour suppression.

Ameloblastic carcinoma: a Brazilian collaborative study of 17 cases.

AIMS: Ameloblastic carcinoma (AMECA) is an odontogenic malignancy that combines the histological features of ameloblastoma and cytological atypia. Because of its rarity, it poses difficulties in diagnosis. The aim of this study was to investigate the socio-demographic data, histopathology, immunohistochemical features, treatment and outcomes of 17 cases. METHODS AND RESULTS: Descriptive statistical analyses were used to portray the clinicopathological data collected, retrospectively. Log-rank tests were performed to determine new prognostic factors. Lesions were immunostained for Ki67, p16, p53, and cytokeratins (CKs), and compared with solid/multicystic ameloblastomas (n = 15). AMECA was mostly diagnosed at a late stage, affecting the posterior mandible of male patients in their fifth decade of life. Recurrence was diagnosed in nearly 90% of treated patients, and metastasis occurred in four patients. The mean number of Ki67-positive cells was 86.4 ± 66 per field. Tumours were focally positive for CK7, CK8, CK14, and CK18, and diffusely positive for CK19, p53, and p16. AMECA showed increased immunoexpression of CK18, CK19, p16, p53 and Ki67 as compared with benign cases. CONCLUSIONS: Our study has contributed to the improved characterization of the epidemiology, prognostic markers, treatment options and outcomes of AMECA. Current criteria must be reviewed to simplify the diagnostic process for these neoplasms.

BRAFV600E mutation in the diagnosis of unicystic ameloblastoma.

BACKGROUND: Unicystic ameloblastoma, an odontogenic neoplasm, presents clinical and radiographic similarities with dentigerous and radicular cysts, non-neoplastic lesions. It is not always possible to reach a final diagnosis with the incisional biopsy, leading to inappropriate treatment. The BRAFV600E activating mutation has been reported in a high proportion of ameloblastomas. The purpose of the study was to assess the utility of the detection of the BRAFV600E mutation in the differential diagnosis of unicystic ameloblastoma with dentigerous and radicular cysts. METHODS: Twenty-six archival samples were included, comprising eight unicystic ameloblastomas (UAs), nine dentigerous and nine radicular cysts. The mutation was assessed in all samples by anti-BRAFV600E (clone VE1) immunohistochemistry (IHC) and by TaqMan mutation detection qPCR assay. Sanger sequencing was further carried out when samples showed conflicting results in the IHC and qPCR. RESULTS: Although all UAs (8/8) showed positive uniform BRAFV600E staining along the epithelial lining length, the mutation was not confirmed by qPCR and Sanger sequencing in three samples. Positive staining for the BRAFV600E protein was observed in one dentigerous cyst, but it was not confirmed by the molecular methods. Furthermore, 2/9 dentigerous cysts and 2/9 radicular cysts showed non-specific immunostaining of the epithelium or plasma cells. None of the dentigerous or radicular cysts cases presented the BRAFV600E mutation in the qPCR assay. CONCLUSIONS: The BRAFV600E antibody (clone VE1) IHC may show non-specific staining, but molecular assays may be useful for the diagnosis of unicystic ameloblastoma, in conjunction with clinical, radiological and histopathological features.

DNA methyltransferase immunohistochemical expression in odontogenic tumours.

BACKGROUND: Odontogenic tumours are a heterogeneous group of lesions formed from tissues that give rise to the tooth. DNA methylation, a covalent addition of a methyl group to the 5-carbon position of a cytosine nucleotide, is considered an important regulator of gene expression. The addition of the methyl radical is catalysed by DNA methyltransferases (DNMTs). Although some epigenetic studies have been conducted in odontogenic tumours, a study with the three types of DNMTs in several different members of this group is missing. This study analyses the expression of DNMTs in odontogenic tumours. METHODS: Formalin-fixed and paraffin-embedded tissue samples of 20 ameloblastomas, 10 calcifying cystic odontogenic tumours, 10 calcifying epithelial tumours, 10 adenomatoid odontogenic tumours, 10 keratocystic odontogenic tumours, five ameloblastic fibromas, two ameloblastic fibro-odontomas, four central odontogenic fibromas, seven peripheral odontogenic fibromas and 10 odontogenic myxomas were included. Immunohistochemical expression of DNMT1, 3A and 3B was assessed using a semi-quantitative analysis, and also a correlation with p21, p27 and E-cadherin immunoexpression was made. RESULTS: DNMT1, 3A and 3B were expressed in the nucleus and/or cytoplasm of all odontogenic tumours. DNMT1 expression was directly correlated with p27 expression in ameloblastomas. CONCLUSION: The high expression of DNMTs in odontogenic tumour cells suggests methylation as an important mechanism for this group of tumours.

Unusual histological patterns and hyaline ring granulomas in a unicystic ameloblastoma.

BACKGROUND: Unicystic ameloblastoma (UA) is a distinct variant of ameloblastoma displaying a large cystic cavity lining by ameloblastomatous epithelium and can present a wide variety of histologic patterns. CASE REPORT: We herein reported an unusual UA occurring in the mandible of a 23-year-old male patient who exhibited luminal, intraluminal and mural patterns, as well as acanthomatous, basal cells and granular cell variants. In addition, hyaline ring granulomas, an extraordinary finding in ameloblastoma, were found. The nature of several microscopic variants in this tumor and the possible significance of their presence have also been discussed. CONCLUSIONS: We believe this to be the first case reported in which a UA displayed multiplicity of histopathological patterns in a single lesion.