Ameloblastoma: a multicentric study

Surgical Resection and Reconstruction of Ameloblastoma: A 13-Year Retrospective Review

BACKGROUND

Ameloblastoma is a locally aggressive, benign tumor presenting in the maxilla and mandible prone to recurrence. Resection greatly limits recurrence; however, reconstruction becomes critical to preserve patients' functionality and esthetics.

PURPOSE

The aim of this study was to describe surgical resection and reconstructive approaches in the treatment of ameloblastoma and compare clinical outcomes to conservative methods of treatment.

STUDY DESIGN, SETTING, SAMPLE

A retrospective case series was completed through analysis of patient records. The study population was composed of patients treated for ameloblastoma at the Royal Brisbane Hospital (Queensland, Australia) in the Oral and Maxillofacial Surgery Unit from January 1, 2008, to December 31, 2020. Patients without histological confirmation of intraosseous ameloblastoma were excluded from the study sample.

PREDICTOR VARIABLE

Not applicable.

MAIN OUTCOME VARIABLE(S)

The primary outcome variable was time to recurrence. Secondary outcome variables included any surgical complications incurred.

COVARIATES

The covariate variables collected included age at diagnosis/treatment, gender, ethnicity, location of lesion and site(s) of involvement, tumor extent, alveolar expansion, histopathological growth pattern, and soft tissue involvement.

ANALYSES

Descriptive statistics were computed for each study variable.

RESULTS

A total of 48 cases of histologically confirmed ameloblastoma were identified (41 mandibular, 7 maxillary) involving 50 excisional operations (44 resections, 6 enucleations). Of these cases, 44 were followed up > 12 months, with a mean length of follow-up time of 65.6 months. No recurrence was detected for resected lesions. One enucleated lesion recurred at 25 months. Thirty-seven reconstructive procedures were undertaken, including 32 immediate free flaps. All reconstructive flaps and grafts survived, and no major complications were recorded.

CONCLUSION AND RELEVANCE

Resection of ameloblastoma limits recurrence and should be considered curative. Immediate microvascular free flap reconstruction of maxillary and mandibular defects from resection of ameloblastoma is safe and predictable.

A Retrospective Analysis of 129 Ameloblastoma Cases: Clinical and Demographical Trends from a Single Institution

Ameloblastomas are benign neoplasms of the jaw, but frequently require extensive surgery. The aim of the study was to analyze the demographic and clinicopathological features of ameloblastoma cases at a single Oral and Maxillofacial Surgery group in the United States.

STUDY DESIGN

A retrospective chart review of patients evaluated for ameloblastoma between 2010 and 2020 at a single tertiary care center. Age, race, sex, tumor size, tumor location, and histological subtypes were recorded.

RESULTS

A total of 129 cases of ameloblastoma were recorded with a mean patient age of 42 ± 18.6 years (range 9-91 years old), male to female ratio 1.08:1. Ameloblastoma presenting in the mandible outnumbered maxilla in primary (118 to 8, respectively) and recurrent cases (8 to 1, respectively). There was a higher prevalence of ameloblastoma in Black patients (61.3%) with mean age of Black patients occurring at 40.5 years and the mean age of White patients occurring at 47.8 years and mean tumor size trended larger in the Black patients (15.7 cm2) compared to White patients (11.8 cm2).

CONCLUSION

Data suggests a strong influence of racial factors on the incidence of ameloblastoma, with regards to size, Black patients with ameloblastoma trended higher and more data is needed to clearly elucidate any relationship between the tumor size and race, as other factors may influence the size (such as time to discovery).

Unicystic ameloblastoma: A retrospective study on recurrent factors from a single institute database

OBJECTIVE

Unicystic ameloblastomas are a variant of ameloblastoma with a definite recurrence rate because of the biological behaviours of the tumour. The risk factors associated with disease recurrence were analysed in this retrospective study.

METHODS

A total of 132 patients with primary unicystic ameloblastoma reported in a tertiary hospital from 2005 to 2015 were analysed to identify the clinic-pathological and radiological factors associated with recurrence using univariate and multivariate Cox regression analyses.

RESULTS

The mean volume was 30.54cm3 ± 12.55 cm3, and this value differed significantly according to recurrence (p < 0.001). Root resorption and bone cortex/soft tissue invasion were also significantly associated with recurrence among unicystic ameloblastoma patients (p = 0.017 vs. p < 0.001, respectively). A new stage classification system was developed to predict disease recurrence of patients. The multivariate Cox regression analysis revealed that the new stage classification system was the only predictor of disease recurrence in unicystic ameloblastoma patients (p < 0.001), regardless of root resorption, position and site characteristics.

CONCLUSIONS

Volume, root resorption and bone cortex/soft tissue invasion were risk factors for disease recurrence among unicystic ameloblastoma patients. The new stage classification was an independent predictor of disease recurrence in patients with unicystic ameloblastoma.

A radiologic-pathologic study of the histopathologic variants of ameloblastomas and their proliferation indices

OBJECTIVES

This study aimed to analyze the clinicoradiologic features and Ki-67 proliferation indices between the histopathologic variants of ameloblastomas (ABs) for possible associations.

STUDY DESIGN

The diagnosis and histopathologic variant were confirmed for all cases by experienced Oral and Maxillofacial Pathologists. Immunohistochemistry for Ki-67 was performed on the most representative formalin-fixed paraffin-embedded tissue block. Demographic, clinical data and radiologic features were analyzed from patient records and available radiographic examinations. The investigators were blinded to the histopathologic variant and proliferation index when the clinicoradiologic features were assessed.

RESULTS

The current study included 116 cases of AB in the final sample. The indolent behavior of the unicystic variant was supported by their low proliferation index and slow growth paired with low frequencies of cortical destruction, loss of teeth, root resorption, and encroachment on anatomical structures. In contrast, the comparatively high proliferation index of the plexiform variant correlated with their fast growth and pain. Furthermore, high radiologic frequencies of cortical destruction, loss of teeth, and encroachment of surrounding anatomical structures supported their more aggressive clinical course.

CONCLUSION

Statistically significant differences were noted between certain variants and Ki-67, location, borders, locularity, and cortical destruction, providing better insight into their biological behavior.

Clinicoradiologic features of ameloblastomas: A single-centre study of 155 cases

BACKGROUND

The purpose of the current study was to report on the clinical presentation and radiologic features of 155 cases of ameloblastoma (AB), representing a detailed, large, single-centre radiologic study.

METHODS

Histologically confirmed cases were reviewed over 11 years. Demographic and clinical data were retrieved from the patient's records. Radiologic information was analysed from available radiographs. The radiologic features of ABs were assessed according to the mean age of presentation and the mean duration of the lesion. The distinguishing radiologic features between adults/children and sex were also evaluated.

RESULTS

A statistically significant correlation existed between loss of border demarcation and advanced mean age. Multilocular lesions were markedly more common in adults compared to children. Multilocular ABs were associated with increased lesion duration and advanced mean age. Radiologic signs of reactive bony changes associated with the tumour presented at the highest mean duration of all bony effects. Bony expansion and cortical destruction were statistically correlated with lesion duration. Tooth impaction was more common in children. Some mandibular lesions reached a significant size, resulting in impingement of the maxillary sinus, zygoma, orbit and pterygoid plates.

CONCLUSION

Due to unfortunate healthcare access constraints, ABs grow to significant sizes and exhibit features not often reported in the literature. The findings of this analysis highlighted the radiologic features of ABs expressed through the mean age and duration of the lesion. This emphasises the significance of timely management of these lesions.

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.

Clinicopathologic Profile and Surgical Modalities in Mandibular Ameloblastoma: A Descriptive Study

BACKGROUND

Ameloblastoma is a benign neoplasm composed of epithelial tissue with invasive and infiltrative behavior at the local level and a high recurrence rate, with various histopathologic patterns and clinical forms. Approximately 85% of conventional ameloblastomas occur in the mandible, most often in the body, angle, and ascending ramus area. The treatment modalities include both conservative and radical treatments. Postoperative follow-up is most important in the treatment of ameloblastoma.

AIMS AND OBJECTIVES

To describe the clinicopathologic profile of mandibular ameloblastoma in patients undergoing different surgical modalities. The primary objective was to describe the clinicopathologic profile and surgical management of mandibular ameloblastoma in patients aged ≥18 years, who had reported to a tertiary dental care center for follow-up during the study period. The secondary objective was to describe the distribution of comorbidities associated with different surgical modalities and reconstructive methods.

SUBJECTS AND METHODS

A total of 34 patients with mandibular ameloblastoma who underwent various surgical modalities between 2011 and 2021 were studied. Information was collected using a predesigned proforma and statistically analyzed.

RESULTS

Thirty-four review cases of ameloblastoma were included in the study. The patients were analyzed concerning age, sex, site, size, clinical presentation, radiographic pattern, histopathologic subtype, type of surgery, and associated comorbidities. Most cases of mandibular ameloblastoma involve the age of 16 to 55 years. The mean age of occurrence was found to be 35.5±13.2. A female preponderance, a tumor size range of 2 to 4 cm, a multicystic variant, involvement of the mandibular body in the premolar-molar area, root resorption, cortical perforation, and a follicular type of histopathologic pattern were the common presentations. Isolated anterior tumors restricted to the incisor/canine region were not found. The common surgical modalities undertaken were conservative methods such as enucleation, and chemical cauterization, and radical methods such as marginal mandibulectomy and segmental resection. Reconstruction using a titanium plate or free fibular graft was performed in the indicated cases. The common comorbidities included difficulty in chewing and loss of facial contour. Recurrence after surgical treatment was rare. Only 9% of cases developed a recurrence within 5 years. No recurrence was noted in cases treated with radical treatment, whereas 50% of cases treated with conservative methods showed recurrence.

CONCLUSION

The age of occurrence, site, and size of the tumor, cortical perforation, root resorption, histopathologic type, and radiographic patterns are widely considered factors in devising a treatment plan for mandibular ameloblastoma. However, there may be rare instances where these tumors behave differently regardless of their innocuous clinicopathologic presentation. Surgical procedures such as segmental resection and marginal mandibulectomy were found to be promising for the eradication of the tumor, and prevention of recurrences and metastasis. However, conservative measures such as enucleation and chemical cauterization were fraught with an increased risk of tumor recurrence and metastasis. Future studies with a larger sample size should focus on the clinicopathologic characteristics of ameloblastoma to elucidate its varied behavior and develop newer and advanced treatment modalities that would provide better surgical and postsurgical outcomes in affected patients.

Potential involvement of polycystins in the pathogenesis of ameloblastomas: Analysis based on bioinformatics and immunohistochemistry

OBJECTIVE

To perform an integrated analysis in identifying novel hub genes that could facilitate the diagnosis and targeted therapy of ameloblastoma.

DESIGN

The expression profiling dataset, GSE38494, was obtained from the Gene Expression Omnibus database. Differentially expressed genes were identified through GEO2R online tool and characterised via Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. The protein-protein interaction network and hub genes were screened using the STRING database and Cytoscape software. Subsequently, an upregulated gene was selected for further validation using the GSE132472 dataset. Further, immunohistochemistry was performed to assess the expression of the selected gene in ameloblastomas, odontogenic keratocysts, dentigerous cysts, and gingival tissues. The diagnostic and therapeutic utility of the selected hub genes were further verified by receiver operating characteristic analysis and the DGIdb database.

RESULTS

We identified six hub genes in ameloblastoma, among which the upregulated gene PKD2 and its related gene PKD1 were further validated. GO functional annotation revealed that PKD2 is involved in cell-cell junction, extracellular exosome, cytoplasm, endoplasmic reticulum, and calcium ion transport. The immunohistochemical analysis showed that the expression of polycystin-1 and polycystin-2, encoded by the PKD1 and PKD2 genes, respectively, was upregulated in ameloblastoma. PKD1 and PKD2 had a high diagnostic utility for ameloblastoma, and allopurinol interacted with the PKD2 gene.

CONCLUSION

Our research indicates that polycystins are highly expressed in ameloblastoma and might be involved in the oncogenesis of ameloblastoma, thus offering a new perspective on the molecular mechanisms and targeted therapies on ameloblastoma.

Keratoameloblastoma: A Report of Seven New Cases and Review of Literature

BACKGROUND

Keratoameloblastoma (KA) is an uncommon and controversial variant of ameloblastoma exhibiting central keratinisation. Due to their rarity, there is limited information in the literature on their clinical, radiologic and histologic features. This study adds seven additional cases of KA to the literature, and reviews the current published literature on this rare entity.

METHODS

KAs were retrospectively reviewed over a 20-year period from three Oral and Maxillofacial Pathology Laboratories. Included cases were examined and the diagnosis confirmed under conventional microscopy. Immunohistochemistry with the use of a monoclonal antibody against calretinin was performed on included cases. The clinical, radiologic and histologic features of the seven new cases of KA were analysed and compared to existing cases in the literature.

RESULTS

KAs presented at a mean age of 40 years with a nearly equal gender distribution and a mandibular predilection (65%). The majority (92%) of cases presented with localised swelling with associated pain in 32% of cases. Mixed density or internal calcifications were noted in 40% of cases. All tumours presented with bony expansion, with cortical destruction noted in 62% of cases. Histologically, all tumours consisted of solid and cystic follicles with surface parakeratinisation and lamellated accumulations of central keratin. In areas the cystic follicles had an epithelial lining suggestive of an OKC. There were focal luminal areas of loosely arranged polygonal cells reminiscent of the stellate reticulum. The basal cells consisted of columnar cells with evidence of palisading and prominent subnuclear vacuolisation. Of the cases treated via tumour resection, 27% presented with tumour recurrence.

CONCLUSION

This case series reports seven additional cases of KA, taking the total to 26 reported cases. The identification of subtle histologic features, including focal stellate reticulum-like central areas, subnuclear vacuolisation and lamellated-type central keratinisation, are key in diagnosing KA. The radiologic features will often indicate signs of aggressiveness such as cortical destruction, differentiating KA from OKC. All cases were completely negative for calretinin IHC, limiting its use in distinguishing KA from OKC. Further large series are needed to expand the current understanding of this rare variant of ameloblastoma.

Effectiveness of the Conservative Surgical Management of the Ameloblastomas: A Cross-Sectional Study

Ameloblastoma is a benign, but locally aggressive odontogenic neoplasm, whose appropriate therapeutic management remains highly debatable. The aim of this study was to evaluate the reliability and effectiveness of the two conservative surgical therapeutic protocols (curettage with peripheral ostectomy only and curettage plus cryotherapy) for the management of ameloblastomas. About 53 cases of the ameloblastomas treated in 9 years were retrospectively analyzed regarding their clinical, histopathologic, radiographic, and therapeutic data. The results and the postoperative complications related to both the therapeutic protocols were also statistically investigated. A slight female preponderance was seen (1.12:1.0) with a mean age of 27.1 years. The posterior mandible was the most affected site and dental involvement was frequently found. Multilocular lesions causing the alterations of the bone cortices were the most common radiographic findings. Recurrences were seen in 9.4% of the cases and although the patients submitted to curettage plus cryotherapy have shown an increased incidence of wound dehiscence, infection, and paresthesia, only bone sequestration proved to be significantly more frequent in this group compared to the patients treated by curettage with peripheral ostectomy only. The incidence of the recurrences following the conservative management is low and cryotherapy use as an adjuvant tool must be rationally considered.

A case of giant ameloblastoma: destructive effect on the facial skeleton and soft tissues of the head and neck

Ameloblastoma is a benign odontogenic tumor characterized by slow growth causing painless facial swelling. The tumor can behave locally aggressively, and may have direct destructive effects on the surrounding soft and hard tissues. This paper reports the unique case of a female patient with giant ameloblastoma of the mandible. Computed tomography (CT) revealed an enormous swelling of the left side of the face, resorption of the affected hemi-mandible, left maxilla, and tissues of the temporal, infratemporal, and pterygopalatine fossae. Pressure from the tumor resulted in displacement and destruction of the facial skeleton, upper aero-digestive tract structures, and some structures of the neck. The patient was treated by radical hemimandibulectomy with removal of the tumorous mass. Precise knowledge of the anatomical structures, and their locations and topographical relationships is required in the diagnosis and treatment plan for each surgical procedure in cases of giant ameloblastoma. CT imaging can be used to determine the extent and exact location of the lesion, revealing other important details that may help in selecting appropriate treatment.

Pediatric Odontogenic and Maxillofacial Bone Pathology: A Global Analysis

BACKGROUND

Although pathology in the maxillary and mandibular bones is rare in young patients, the differential diagnosis is broad. The World Health Organization (WHO) updated its classification of maxillofacial bone pathology in 2017. Using these updated guidelines, a systematic review of common maxillofacial bone lesions in the pediatric population was performed.

METHODS

A PubMed search was conducted capturing English language articles from inception to July 2020. Thirty-one articles were identified that described the frequency of maxillofacial bone pathology. Data were extracted and organized using the WHO 2017 classification of odontogenic and maxillofacial bone tumors. Prevalence data were analyzed among diagnostic categories and geographical regions. The SAS version 9.4 was used to complete statistical analyses.

RESULTS

The articles included patients from birth to a maximum age of 14 to 19 years. The most common odontogenic cysts included radicular cyst (42.7%) and dentigerous cyst (39.0%) followed by odontogenic keratocyst (15.0%). Among odontogenic bone tumors, odontoma (49.3%) was most common followed by ameloblastoma (29.1%). The most common nonodontogenic bone tumor was fibrous dysplasia (42.4%), and the most common malignant bone tumor was osteosarcoma (75.0%). Significant variations were found by geographic region, with dentigerous cyst more common than radicular cyst, and ameloblastoma more common than odontoma in African and Asian countries (P < 0.0001).

CONCLUSIONS

This systematic review uses the WHO 2017 guidelines to classify common odontogenic and nonodontogenic maxillofacial bone lesions around the world. Pathogenesis, presentation, and available treatment options for the most common maxillofacial bone lesions are reviewed.

Acanthomatous Ameloblastoma: An Early Stage Case Report with Difficult Management

A case of a mandibular acanthomatous ameloblastoma, with an admixed little component of follicular type, is reported. The epidemiological features of the present case agree with those reported in the international literature. Clinico-radiographic differential diagnostic difficulties existed with several other noncystic osteolytic lesions of the mandible. Recurrence was diagnosed early 1 year after the initial excisional biopsy, and a definitive rim resection was therefore performed. No further recurrence occurred in the following 4-year follow-up.

Training the Trainers in Microsurgery: A Success Story from Vietnam's Hanoi National Hospital of Odonto-stomatology

Background:

Microsurgery is a highly specialized skill that requires advanced training. This is a recount of the 12-year development of Hanoi National Hospital of Odonto-Stomatology (NHOS) from a basic plastic surgery unit to a high-volume, subspecialized reconstructive center.

Methods:

We present a 12-year retrospective account of the development of NHOS with a brief summary of microsurgical reconstructive outcomes.

Results:

From 2008 to 2020, NHOS has performed 665 microsurgical flaps for reconstruction of various maxillomandibular defects. In the pioneering stage (2008-2011), without surgical microscopes, all five free flaps failed. After acquiring a microscope and mentoring from Hanoi's 108 Military Hospital, mandibular bone defect reconstruction with free fibula flaps had 85% success rate. In the growth stage (2012-2015), reconstruction advanced toward more complex defects requiring soft tissue, with a 98.7% success rate. The maturation stage (2016-2020) focused on refinement of reconstructive service to provide subspecialized care for malignant head and neck cancer patients with help from Taiwan's E-Da Hospital and Operation Smile's charity program. The charity mission trips were structured to facilitate good quality teaching rather than hit a quantitative goal of the number of surgeries done. And with a success rate of 99.4%, we have begun further education of the plastic surgery community in Vietnam.

Conclusions:

Our rapid 12-year maturation into a high-volume, subspecialized microsurgical center is the embodiment of the generous efforts of many international friends who invested their time and expertise. And we highly recommend charity mission trips to adopt the “training the trainers” concept to maximize lasting, local impact.

Controversies in ameloblastoma management: evaluation of decision making, based on a retrospective analysis

BACKGROUND

The ameloblastoma management is still challenging to the high recurrence rates and significant morbidity associated with radical treatment. The purpose of this 10-year retrospective study was to analyze the influence of ameloblastoma type and treatment strategy on the long-term outcomes and recurrence rates.

MATERIAL AND METHODS

The retrospective analyses of 64 histologically-confirmed ameloblastoma cases was performed. The possible risk factors for recurrence and the development of complications were estimated statistically.

RESULTS

The treatment strategy applied for this group of patients was the following: thirty-four patients (53.1%) were treated conservatively with enucleation or extended bone curettage. Radical treatment (bone resection) was applied in 30 (46.9%) cases. The follow-up period ranged from 2 to 10 years (mean value 4.28 ± 3,26). General recurrence rate consisted 32.8%. This study did not find significant correlations between clinical or histopathological features of the ameloblastoma and the recurrence rate. The only factor that significantly influence recurrence rate was the treatment strategy (41% in conservative treatment vs 15% in radical treatment, p<0.05). Postoperative complications were observed in 42 patients (65.6%) and included face asymmetry and disfigurement (17.2%), temporary paresthesia of the inferior alveolar nerve (IAN) - 23.4%, permanent paresthesia of IAN - 20.3%, paresis of a marginal branch of the facial nerve - 6.3%, infection 12.5%, and swelling - 20.3%. The complication rates, esthetic and functional deficiency were significantly higher in radically treated patients (p<0.05) Conclusions: Our study confirms that higher recurrence rate is associated with conservative treatment for ameloblastoma, while radical treatment leads to an increased number of postoperative complications that affect the patient's quality of life.

A Retrospective Study of 158 Cases on the Risk Factors for Recurrence in Ameloblastoma

Background: Ameloblastoma is an odontogenic tumor occurring in jaws, with local aggressiveness and postoperative recurrence. This study was aim to investigate the clinical and radiographic risk factors for recurrence in ameloblastoma. Methods: Patients diagnosed with ameloblastoma between March 2009 and March 2019 were retrospectively analyzed. Clinical and Radiological data and follow-up records were collected. Survival analyses were performed by Kaplan-Meier and log-rank tests, as well as Cox proportional hazards model. Results: One hundred and fifty-eight patients (104 males and 54 females were enrolled. The overall recurrence rate for ameloblastoma was 13.29%, and 10.76% recurred within 5 years. Most of the tumors were located in mandible (86.71%), while the rest 21 cases were in maxilla (13.29%). More than half cases (55.06%) showed multilocular radiolucency, 61 cases (38.61%) showed unilocular radiolucency. Significant differences were found with amelobastoma recurrence rate related to treatment modality, impacted tooth and root resorption (P =0.002, 0.022 and 0.007 respectively). Conclusions: Treatment modality, impacted tooth and root resorption all showed statistically significant associations with the recurrence rate in ameloblastoma. However, due to the limitation of this study, further studies are needed to reveal the true mechanism of ameloblastoma recurrence.

Tomoelastography for non-invasive detection of ameloblastoma and metastatic neck lymph nodes

Ameloblastoma is a benign epithelial tumour and the most common odontogenic tumour, accounting for about 18% of cases. We present a patient to illustrate the first use of tomoelastography for quantitatively mapping tissue stiffness (shear wave speed) and fluidity (loss angle of the complex shear modulus) in a metastasised ameloblastoma of the left mandible. Tomoelastography maps clearly depicted the extent of the tumour by abnormally high values of stiffness and fluidity (1.73±0.23 m/s, 1.18±0.08 rad) compared with normal values in the contralateral mandible (1.04±0.09 m/s, 0.93±0.12 rad). Abnormal stiffness also revealed metastatic involvement of the neck lymph nodes (1.30±0.03 m/s vs 0.86±0.01 m/s). Taken together, stiffness and fluidity measured by tomoelastography can sensitively detect the presence and extent of bone tumours and metastatic spread to cervical lymph nodes.

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.

Discovery of novel molecular characteristics and cellular biological properties in ameloblastoma

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

Odontogenic keratocyst and ameloblastoma: radiographic evaluation

OBJECTIVES

To describe the radiographic features of odontogenic keratocysts (OKCs) and ameloblastomas and to compare the radiographic findings between these 2 lesions.

METHODS

Radiographs of OKCs and ameloblastomas were retrospectively reviewed. Location, border, shape, association with impacted tooth, tooth displacement, root resorption, and bone expansion were evaluated. Chi-squared or Fisher's exact tests were used for statistical analysis. A p value < 0.05 was considered to indicate statistical significance.

RESULTS

One hundred OKCs and 101 ameloblastomas were reviewed. The ratios of maxilla to mandible were 1:1.4 and 1:9.1 in OKCs and ameloblastomas, respectively. All evaluated features significantly differed between OKCs and ameloblastomas (p ≤ 0.001). Most OKCs showed smooth border (60%) and unilocular shape (82%), while most ameloblastomas showed scalloped border (77.2%) and multilocular shape (68.3%). Association with impacted tooth was found in 47% of OKCs and 18.8% of ameloblastomas. Adjacent tooth displacement was found in 33.7% of OKCs and 55.8% of ameloblastomas. Root resorption was more common in ameloblastomas (66.7%) than in OKCs (7%). Bone expansion was also more common in ameloblastomas (96.3%) than in OKCs (63.6%).

CONCLUSION

A unilocular radiolucent lesion with smooth border, no adjacent tooth displacement, no root resorption and causing mild or no bone expansion is suggestive of an OKC rather than an ameloblastoma.

Recurrence factors in pediatric ameloblastoma: Clinical features and a new classification system

BACKGROUND

Ameloblastomas of jaw in the pediatric population are a rare clinical entity and have not been well addressed in the literatures. The present retrospective study analyzed the risk factors associated with recurrence of pediatric ameloblastomas.

METHODS

Cases of primary pediatric ameloblastomas seen in a tertiary hospital between 2005 and 2015 were analyzed to identify the clinical factors associated with recurrence.

RESULTS

There were a total of 104 cases of primary pediatric ameloblastomas. The overall mean maximum tumor diameter was 4.11 ± 1.339 cm. The receiver operating characteristic curve and the Youden Index showed an optimal cutoff point of 4.95 cm to accurately predict recurrence. Bone cortex/soft tissue invasion were associated with tumor recurrence (P < .001).

CONCLUSIONS

The maximum tumor diameter, root resorption, and bone cortex/soft tissue invasion were risk factors for recurrence of pediatric ameloblastomas. The new classification system may serve as a predictor of recurrence in pediatric ameloblastomas.

Radiographic estimation of the growth rate of initially underdiagnosed ameloblastomas

BACKGROUND

To evaluate the specific growth rate (SGR) of ameloblastoma.

MATERIAL AND METHODS

cases of ameloblastoma initially underdiagnosed (e.g. cases overlooked or diagnosed as reactive lesions) which had adequate radiographic documentation to evaluate their progression were retrospectively selected. Two panoramic radiographs were analyzed to determine the specific growth rate (SGR) of each tumor, defined as the logarithm of the ratio of final tumor area (when the diagnosis of ameloblastoma was made) to the initial tumor area (when the lesion was underdiagnosed), divided by the time interval between the radiographic images. The tumor area was measured using the software ImageJ.

RESULTS

Twelve patients with mandibular ameloblastomas were selected, including 5 males and 7 females, with a mean age of 24.9 years (range: 14-61 years). In four cases, the lesion was associated with the crown of an impacted third molar. In three cases, it was initially diagnosed as a periapical lesion. Three cases were extrafollicular and were not noticed in the initial radiographs. Two cases were initially diagnosed as ameloblastoma, but the surgery was delayed for personal reasons. The mean interval of time between the two radiographic images was 4.3 years (range: 0.4-9 years). Based on our analysis, ameloblastoma grows in average 40.4% per year (range: 14.9-88.7%).

CONCLUSIONS

Ameloblastoma is a progressively growing tumor, but its growth rate seems to be smaller than initially reported in the literature. Better understanding the radiographic progression of ameloblastoma might improve its early diagnosis, management, and prognosis.

Global incidence and profile of ameloblastoma: A systematic review and meta-analysis

OBJECTIVES

To evaluate the global incidence of ameloblastoma and to provide a profile of ameloblastoma patients.

MATERIAL AND METHODS

A systematic review and meta-analysis was conducted. Searches were performed in PubMed, EMBASE, SCOPUS, and Web of Science for articles published from 1969 to 2018 for the global incidence and from 1995 to 2018 for the profile of ameloblastoma patients.

RESULTS

Seven studies on the incidence rate of ameloblastoma were included in the meta-analysis. These studies only covered Europe, Africa, and Australia. The pooled incidence rate was 0.92 per million person-years (95% CI: 0.57-1.49), with significant heterogeneity between studies. Forty-two articles provided profile data of 6,446 ameloblastoma patients. Mean age was 34 years and the peak age incidence in the third decade of life. In Europe and North America, ameloblastoma mostly occurred at an older age when compared to Africa and South America. A slight male preference (53%) was found, and the mandible appeared to be the preferred site. The most common type of ameloblastoma was multicystic. The histopathologic patterns were mostly follicular and plexiform.

CONCLUSIONS

This is the first study assessing the global incidence of ameloblastoma. The pooled incidence rate was determined to be 0.92 per million person-years.

Ameloblastoma: a retrospective single institute study of 34 subjects

Objective: This study aims to clarify demographic and clinical aspects of patients with ameloblastoma treated at a single Finnish institute during 1985-2016. Associations between predictor variables (gender and age) and outcome variables (location, tumour type, growth patterns and average tumour size) were sought.Materials and methods: A retrospective cohort study was designed and implemented including 34 patients diagnosed with primary ameloblastoma and treated at the Helsinki University Central Hospital. Patient records were investigated, and tissue samples re-evaluated. The chi-square test was used on all categorized variables and t-test for continuous ones. A p value equal to or under .05 was considered significant.Results: Males were slightly more predominant among the Finnish patients with ameloblastoma. Maxillary tumours were seen exclusively in male patients (p = .034). Additionally, these patients were older than patients with mandibular tumours (p = .007). A mixture in histological growth patterns was more common than originally anticipated. The study revealed a wide range of clinical signs and subjective symptoms, of which pain or other sensations were experienced most often.Conclusions: This study of 34 subjects shows that southern Finnish patients with ameloblastoma do not substantially differ from patients in similar study designs.

Radical vs conservative treatment of intraosseous ameloblastoma: Systematic review and meta-analysis

OBJECTIVES

The aim of the present study was to assess the outcomes of radical and conservative treatment approaches of solid/multicystic and unicystic ameloblastoma in terms of recurrence rates.

MATERIAL AND METHODS

A systematic review and meta-analysis was conducted based on the PRISMA statement. Search was performed using PubMed, Embase, SCOPUS, and Web of Science for articles published from January 1969 until March 2018. Quality assessment of the selected articles was conducted using the Quality Appraisal of Case Series Studies Checklist. The meta-analysis was performed using the MedCalc program.

RESULTS

The search strategy yielded 6,984 articles; 20 studies met the eligibility criteria and were included in the meta-analysis. The pooled recurrence rate of solid/multicystic ameloblastomas following radical treatment was 8%, while conservative treatment caused recurrences in 41%. For unicystic ameloblastomas, these values were 3% and 21%, respectively. The risk of recurrences in both types of ameloblastomas following radical treatment was lower than following conservative treatment.

CONCLUSIONS

The present study showed statistically significant differences in recurrence favoring radical treatment for both unicystic and solid/multicystic ameloblastoma. The solid/multicystic type showed more recurrences than the unicystic type. Unfortunately, since only retrospective studies were available, the evidence is less strong as wished for.

Odontogenic tumors and lesions treated in a single specialist oral and maxillofacial pathology unit in the United Kingdom in 1992-2016

OBJECTIVES

Odontogenic tumors (ODTs) are a heterogeneous group of lesions derived from elements of tooth-forming tissues. No detailed data on the incidence of odontogenic tumors in the United Kingdom have been published. The aim of this study was to retrospectively describe the range and incidence of odontogenic tumors from 1992 to 2016 in a single specialist unit and to compare this population with others.

STUDY DESIGN

By using the Oral and Maxillofacial Pathology database, Sheffield (UK), we included both local and referred consultation cases. A proportion of diagnoses were reclassified in accordance with the 2017 World Health Organization classification.

RESULTS

In total, 559 odontogenic tumors were diagnosed. Overall, the most common lesions were ameloblastoma (196 [33.8%]), odontoma (148 [25.5%]), and odontogenic myxoma (37 [6.3%]), but this varied between local and referral case populations, with odontomas being most common in the local population (43%). The sites affected and the gender and age of patients were similar to other Western populations. Malignant ODTs comprised 33 cases (5.7%), of which 9 (27.3%) were ameloblastic carcinoma. The majority of the malignant ODTs comprised referral cases.

CONCLUSIONS

Here, we present the first detailed data on ODTs within a UK population, and the pattern of incidence from the local population is similar to other Western populations. The exceptional rarity of malignant ODTs emphasizes the need for specialist centers for their treatment to gain diagnostic experience.

Maxillary ameloblastoma: results of the treatment in 11 patients

Introduction: Surgery of maxilla ameloblastoma is mutilating and the tumor propensity for recurrence high. Patients and Methods: The oral and visual functions, facial morphology and tumor recurrence in 11 patients after maxillary ameloblastoma surgery are retrospectively reviewed. Results: Facial morphology was satisfactory in 7 patients who had all tumor removal by a type 1 or 2A maxillectomy and surgical wound closure. Out of these patients, 4 who had dental rehabilitation by conventional prosthesis presented satisfactory mastication. Four patients subjected to the tumor removal by a type 3 maxillectomy had all facial asymmetry. Out of these, 1 patient who did not have the orbital floor defect repair presented diplopia and enophtalmos, 2 patients subjected to the palate defect repair by a prosthetic obturator or oral mucosa had elocution impairment. The tumor recurrence occurred in 2 patients after tumor enucleation and in 1 patient after radical surgery out of 8 patients who had a postoperative follow-up. Discussion: In ameloblastoma surgery, achieving both the tumor recurrence prevention and a satisfactory facial reconstruction is challenging. Conclusion: Avoiding the tumor recurrence should be the major goal when patient post-surgical follow-up cannot be guaranteed.

Ameloblastoma: current etiopathological concepts and management

Ameloblastoma is a benign odontogenic tumor of epithelial origin. It is locally aggressive with unlimited growth capacity and has a high potential for malignant transformation as well as metastasis. Ameloblastoma has no established preventive measures although majority of patients are between ages 30 and 60 years. Molecular and genetic factors that promote oncogenic transformation of odontogenic epithelium to ameloblastoma are strongly linked to dysregulation of multiple genes associated with mitogen-activated protein kinase, sonic hedgehog, and WNT/β-catenin signaling pathways. Treatment of ameloblastoma is focused on surgical resection with a wide margin of normal tissue because of its high propensity for locoregional invasion; but this is often associated with significant patient morbidity. The relatively high recurrence rate of ameloblastoma is influenced by the type of molecular etiological factors, the management approach, and how early the patient presents for treatment. It is expected that further elucidation of molecular factors that orchestrate pathogenesis and recurrence of ameloblastoma will lead to new diagnostic markers and targeted drug therapies for ameloblastoma.

Analysis of Prevalence and Clinical Features of Ameloblastoma and its Histopathological Subtypes in Southeast Myanmar and Lower Northern Thailand Populations: A 13-Year Retrospective Study

INTRODUCTION

Prevalence of ameloblastomas has been established worldwide but collective data of ameloblastoma in Southeast Asian countries has not been well analyzed.

AIM

Aim of this study was to report analysis and comparison of the prevalence and demographic data of clinical features of ameloblastoma and its histopathological variants in Southeast Myanmar and lower Northern Thailand populations.

MATERIALS AND METHODS

A retrospective study on ameloblastoma was performed based on the availability of oral biopsy specimens in Faculty of Dentistry, Naresuan University, Phitsanulok, Thailand, between January 2002 and August 2015. The collected data were subjected to descriptive statistical analyses with the SPSS version 17.0 statistical software package (SPSS Inc., Chicago, USA). Pearson's chi square (χ2) test and t-test were employed. The critical level of significance was set at p<0.05.

RESULTS

Total of 616 cases were reviewed, 30 cases (5%) were diagnosed as ameloblastoma with male:female ratio of 1.14:1. The mean age of the patients was 31.3±15.6 years. The predominance anatomical distribution was observed in the mandible (86.7%). Posterior body-ramus-angle region was the most common site. Almost all cases were asyptomatic and most common clinical manifestation was swelling of affected region. Multilocular radiolucency was observed in 70% of cases, whereas 30% were unilocular. Three subtypes of ameloblastomas were diagnosed: unicystic ameloblastoma (20%), conventional solid/multicystic ameloblastoma (70%), and desmoplastic ameloblastoma (10%). The most common histologic pattern was the plexiform type (57.2%) followed by follicular type (23.8%).

CONCLUSION

Prevalence of ameloblastoma in Southeast Myanmar and lower Northern Thailand populations correspond with data from other geographic areas of Thailand and other Asian countries. However, some demographic and histopathological profiles are different, with plexiform ameloblastoma being the most common subtype in this study.

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.

Ameloblastoma: demographic data and treatment outcomes from Melbourne, Australia

BACKGROUND

There is a lack of published data on the demographics and treatment outcomes of ameloblastomas treated in Australia. Our objective was to collect this data and compare the findings to other international studies.

METHODS

A retrospective study of 42 patients with ameloblastoma was conducted at The Royal Melbourne Hospital, Australia. Data on the demographic features, management techniques (ablative and reconstructive), and outcomes were collected and analysed.

RESULTS

The majority of tumours were solid/multicystic (81%) and occurred most commonly in the mandible (80.5%). Unicystic ameloblastomas affected a younger age group, with Type 3 being the most common subtype. Overall, the recurrence rate for solid/multicystic ameloblastomas was 14.7%; however, radical surgery was found to have a significantly lower recurrence rate when compared to conservative management (p=0.015), with a mean of 51 months follow-up. Results indicated that vascularized free-flaps had fewer postoperative complications than non-vascularized bone grafts; however, the differences did not reach statistical significance.

CONCLUSIONS

This is the largest clinicopathological study regarding ameloblastoma management from Australia, and our results support the current literature in recommending radical surgery for the treatment of solid/multicystic and Type 3 unicystic tumours.

Immunohistochemical expression of Survivin and its relationship with cell apoptosis and proliferation in ameloblastomas

Ameloblastoma behavior is related to the potential of tumor cells to inhibit apoptosis and to initiate a proliferative phase. This study was performed to compare the immunoexpression of Survivin with Bcl-2, Bax, and Ki-67 and to associate them with the histopathological type of each variant of ameloblastoma.

MATERIAL AND METHODS

Using the World Health Organization (WHO) criteria for ameloblastoma, 110 cases were selected. The cases were classified as solid/multicystic and unicystic ameloblastomas. Cellular counts of cytoplasmic immunoexpression were assessed for cytoplasmic Survivin, Bcl-2, and Bax, while the nuclear immunoexpression of Survivin and Ki-67 was assessed using label index.

RESULTS

Cytoplasmic Survivin and Bcl-2 showed higher percentages of immunoexpression in solid multicystic ameloblastomas compared to unicystic ameloblastomas (P < 0.05). Bax, Ki-67, and nuclear Survivin were expressed in higher percentages in unicystic ameloblastomas.

CONCLUSIONS

Cytoplasmic Survivin and Bcl-2 immunoexpression levels were elevated in relation to Bax immunoexpression, suggesting aggressive ameloblastoma behavior, while Ki-67 and nuclear Survivin immunoexpression may be associated with the type of tumor morphology that influences cellular counts or with the greater capacity for cellular proliferation and tumor growth.

Immunoexpression of Ki-67, MCM2, and MCM3 in Ameloblastoma and Ameloblastic Carcinoma and Their Correlations with Clinical and Histopathological Patterns

Cell proliferation assays are performed using antibodies against nuclear proteins associated with DNA replication. These nuclear proteins have gained special interest to predict the biological and clinical behaviors of various tumors. The aim of this study was to analyze the presence of Ki-67 protein and the minichromosome maintenance-2 (MCM2) and maintenance-3 (MCM3) proteins in ameloblastoma. Materials and Methods. Cell proliferation marker expression levels were assessed via immunohistochemistry in 111 ameloblastoma cases (72 unicystic ameloblastoma samples, 38 solid/multicystic ameloblastoma samples, and 1 ameloblastic carcinoma). The label index was performed as described previously. Results. MCM2 and MCM3 showed higher proliferation indexes in all variants of ameloblastoma compared to the classic marker Ki-67. No correlation between the proliferation index and the clinical and protein expression data was observed. Conclusion. The results suggest that clinical features do not directly affect tumor cell proliferation. Moreover, the high levels of cellular proliferation of MCM2 and MCM3 compared with Ki-67 may indicate that MCM2 and MCM3 are more sensitive markers for predicting the growth rate and eventually might be helpful as a tool for predicting aggressive and recurrent behaviors in these tumors.

Epidemiology of ameloblastomas of the jaws; a report from the Netherlands

Objectives: To provide epidemiological data of ameloblastomas of the jaws in the Netherlands over a 25-year time period (1985-2010) and to compare these data with data from other parts of the world. Material and Methods: The data of all patients diagnosed with a primary ameloblastoma of the jaws in the Netherlands in the period 1985-2010 have been retrieved from the nationwide histopathology and cytopathology network and registry in the Netherlands (PALGA). The pathology reports were screened and only those cases were included in which a distinct diagnosis of primary, histopathologically benign, intraosseous ameloblastoma was rendered. The average population in The Netherlands during this period amounted approximately 15 million people. Results: An annual incidence rate was approximately 1,5 per million population, the male-female ratio being 1.4: 1. The age at the time of diagnosis was 44.1 years. The average age in males was 46.3 years compared to an average age in females of 41.3 years, the difference being significant (p≤ 0.05). The results were compared with those available in only a small number of publications worldwide. Conclusions: There is no strong evidence for significant differences of the true incidence of ameloblastomas worldwide, neither for a gender predilection. The diagnosis is generally made at a somewhat lower age in women; this phenomenon is even much stronger in the Black population, irrespective of gender. No proper explanation for this finding can be provided.

Key words:Odontogenic tumor, ameloblastoma, epidemiology.

Ameloblastomas: clinicopathological features from 70 cases diagnosed in a single oral pathology service in an 8-year period

Ameloblastomas are odontogenic tumors that can present some distinct clinicopathological profiles when comparing different populations and studies. Objectives: The aim of the present study was to analyze the clinicopathological features from a series of ameloblastomas diagnosed in a single Oral Pathology service in Brazil in an 8-year period. Study Design: The files were revised and all cases diagnosed as ameloblastomas in the period were retrieved. All hematoxylin and eosin stained histological slides were reviewed and all clinical and radiological information were obtained through a review of the laboratory forms. Data were descriptively analyzed and a comparison was performed with the different ameloblastomas subtypes. Results: Seventy ameloblastomas composed the final sample, including 57 (81%) solid/multicystic, 9 (13%) unicystic, 2 (3%) desmoplastic and 2 (3%) peripheral ameloblastomas. Mean age of the affected patients was in the forth decade of life and there was a slight male predominance. Most tumors presented as multilocular radiolucencies, were located in the posterior mandible and showed the follicular and plexiform histological patterns. There was no difference on the mean age of the patients affected by solid and unicystic ameloblastomas. Conclusions: The present results showed that the clinicopathological features of the ameloblastomas included in this Brazilian sample were similar to the features described in most other worldwide populations.

Key words:Ameloblastoma, solid, unicystic, review, epidemiology, histology.