Conceptual changes in ameloblastoma: Suggested re-classification of a "veteran" tumor

Classic Desmoplastic Ameloblastoma: Should It Be a Distinct Subtype of Ameloblastoma?-Based on Clinicopathological, Radiological, Immunohistochemical and Molecular Study of a Large Cohort

OBJECTIVES

To identify whether the classic desmoplastic ameloblastoma (DA) is an independent subtype of ameloblastoma.

MATERIALS AND METHODS

Eighty-six classic DA and 28 hybrid DA cases were retrieved, and available clinical, radiological, and histopathological data were collected. DNA from microdissected tumor tissues were utilized for BRAF V600E, SMOL412F, and CTNNB1 mutation detection. Data of classic DA and hybrid DA were analyzed and compared with each other and with previous reports of conventional ameloblastoma (CA).

RESULTS

69.8% (60/86) of classic DA occurred in the mandible, with the majority affecting the anterior-premolar regions. They were characterized as osteolytic bone expansion (33.8 ± 12.8 mm) with internal bone/calcification (57/58, 98.3%) in radiology. Genetically, classic DA exhibited a high incidence of BRAF V600E mutation (58/62, 93.5%) but no CTNNB1 and SMO L412F mutations. Hybrid DA exhibited similarities to CA in jawbone location, tumor size, and radiology. The recurrence rate of classic DA (9.2%) was lower than that of CA (25.8%).

CONCLUSION

High anterior-premolar distribution, a mixture of osteolytic and internal high-density shadows in radiology, smaller tumor size, compressed epithelium with abundant stroma and scattered bone, consistent mutation of BRAF V600E, and better prognosis all suggest that classic DA may be a distinct clinicopathological subtype of ameloblastoma.

Risk Factors and Nomogram for Predicting the Recurrence of Conventional Ameloblastoma

OBJECTIVE

To identify risk factors for the recurrence of conventional ameloblastoma (AM) and develop a predictive nomogram model for postoperative recurrence.

METHODS

Clinical, pathological, and radiographic data from 235 patients treated at the Hospital of Stomatology, Sun Yat-sen University (2005-2022) were retrospectively analyzed. Logistic regression identified independent prognostic factors, and a nomogram model was constructed using R software.

RESULTS

Multilocularity, cortical bone perforation, and inferior alveolar nerve involvement significantly increased recurrence risk in conventional AM (p < 0.05). Logistic regression analysis revealed that multilocular tumors (OR = 3.68, p = 0.002), honeycomb patterns (OR = 10.80, p < 0.001), and cortical bone perforation (OR = 2.62, p = 0.011) were significantly associated with increased recurrence risk. Surgical approaches significantly impacted recurrence rates, with curative resection surgery (CRS) resulting in the lowest recurrence risk as compared with fenestration decompression (FD) and local curettage (LC). CRS and curettage and fenestration decompression (CFD) were identified as effective protective factors against recurrence (p < 0.001). A nomogram model with high predictive accuracy (AUC = 0.867) was developed.

CONCLUSION

Multilocularity, cortical bone perforation, and inferior alveolar nerve involvement significantly increased the risk of recurrence. The nomogram model provided effective risk assessment for clinical decision-making.

From pathogenesis to precision medicine: Transformative advances in research and treatment of ameloblastoma

Odontogenic neoplasms of the jaw are dominated by ameloblastoma (AM), a locally aggressive epithelial tumor with a significant propensity for recurrence. The World Health Organization's 2022 update to the AM classification system underscores recent progress in comprehending its underlying mechanisms and refining clinical approaches. Contemporary research has yielded significant insights into the genetic underpinnings of AM, paving the way for the development of precision-based treatment strategies. Advanced genetic profiling has revealed a significant frequency of BRAF (V-raf murine sarcoma viral oncogene homolog) V600E and SMO (Smoothened) gene alterations in AM. Importantly, therapeutic interventions specifically designed to target these genetic aberrations, including BRAF and MEK pathway blockers, have shown encouraging results in terms of both effectiveness and tolerability, as documented in individual case reports and small-scale clinical investigations. This comprehensive review summarizes the recent modifications to the World Health Organization's categorization of AMs, explores progress in elucidating their underlying molecular pathways, and evaluates emerging targeted treatment modalities. Our objective is to present a thorough synthesis of contemporary scientific discoveries and therapeutic interventions, potentially paving the way for more efficacious and individualized clinical management protocols for this complex neoplasm.

Panorama of Odontogenic Tumours and Cystic Lesions of Jaw: A Single Institutional Experience

Odontogenic tumours are relatively rare tumours presenting with varied behaviour ranging from hamartomatous lesion to malignant neoplasm. Majority of them are benign, whereas few cases are malignant which may arise de novo or in background of benign tumour. The aim of this study is to evaluate the pattern of presentation, epidemiological characteristics, histological types and management of a series of odontogenic tumours and cystic lesions of jaw. A prospective observational study was undertaken on all treated cases of odontogenic tumours and cystic lesion of jaw in the Department of Surgical Oncology of a state-affiliated Regional Cancer Centre of Tamil Nadu. Twenty-six cases fulfilled the inclusion criteria of the total 32 cases of odontogenic tumour and cystic lesions of jaw encountered at our institution between february 2021 and july 2023 were enrolled for study. The epidemiological data, clinical presentation and modalities used for treatment were noted and data analysis done with SPSS software. Ameloblastoma was the most common pathology accounting for 50% of total cases. Ameloblastoma was commonly present in male, with male to female ratio of 3:1 and a relatively uniform distribution through 2nd to 7th decade, with a mean diameter of 9.3 cm. Mandibular/maxillary resection was needed for 91.7% cases. Cervical lymph nodes were enlarged in 31% of cases of ameloblastoma but none was metastatic. Other pathologies identified were cemento-osseus fibroma (7.7%), odontogenic myxoma (7.7%) and odontogenic keratocyst (7.7%). Mandible was commonly involved site in 93% in odontogenic tumour. No case of recurrence was noted amongst 81% cases on follow-up. Ameloblastoma is the most common histology amongst all odontogenic tumours and cystic lesion of jaw. Indolent course leads to large dimensions of these tumours with treatment challenge and some forms of mandibular/maxillary resections are required for majority of cases thus incurring variable degree of morbidity. On contrary, larger the diameter of tumour required less of flap reconstruction due to redundant skin and mucosa post excision of tumour. There is low recurrence rate with margin negative resections.

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.

Recurrence and malignant risk of ameloblastoma: A demographic study of 1626 cases from east China

BACKGROUND

Ameloblastoma is characterized by aggressive nature, high recurrence rate, occasional malignant transformation, but recurrence and malignant incidence of ameloblastoma are not yet addressed by a large-scale case series study.

MATERIALS AND METHODS

This study provided a detailed description of the relationship between demographic characteristics and recurrence and malignant cases with different clinical types of ameloblastoma (n = 1626).

RESULTS

The overall incidence of recurrence and malignancy was 17.2 % and 3.4 %, respectively. Notably, we observed that there were multiple recurrent episodes (mean time, 24.3-28.7 months) among ameloblastoma patients. Multivariate analysis revealed that age of > 45 years (odds ratios (OR), 2.10; 95 % confidence interval (CI), 1.17-3.76), male (OR, 3.24; 95 %CI, 1.49-6.99), maxilla (OR, 5.58; 95 %CI, 3.11-10.0), and pre-existing recurrence (OR, 3.79; 95 %CI, 2.05-7.01) as independent factors were associated significantly with increased risk of malignancy.

CONCLUSION

Identification of the clinical factors responsible for increased risk of malignancy provides better insight in management planning for ameloblastoma.

Pseudocarcinomatous Squamous Hyperplasia After Surgical Management Of Pediatric Ameloblastoma: An Immunohistochemical Study

Pseudocarcinomatous squamous hyperplasia (PSH) affecting the jaws is uncommon. The mandible is the most common location, usually as a complication associated with osteomyelitis, medication-related osteonecrosis or osteoradionecrosis. Herein, we report an 8-year-old male patient presenting a solid ameloblastoma, plexiform type, who was treated by segmental mandibulectomy with bone grafting. Three months later, on the underlying graft, a sinus tract was observed, and a small bone fragment was resected which was diagnosed as bone sequestration associated with PSH. After 7-year follow-up, the patient is well, without alterations. To our knowledge, for the first time, we report in detail the immunohistochemical features of PSH which, in addition to epithelial component profile and chronic inflammatory cells, revealed a diffuse infiltration by dendritic cells, suggesting that epithelial cell-immune cell interactions in PSH pathogenesis should also be considered.

Update from the 5th Edition of the World Health Organization Classification of Head and Neck Tumors: Odontogenic and Maxillofacial Bone Tumours

The 5^th edition of the World Health Organization (WHO) Classification of Head and Neck Tumours (2022) comes out only five years after the previous edition, however it presents important updates that run in parallel with the rapid progression involving the increasingly sophisticated molecular investigation and its interpretation, some of which already have therapy-related impact. This manuscript provides an overview of the leading changes introduced in the classification of Odontogenic and Maxillofacial Bone Tumours that encompasses cysts of the jaws, odontogenic tumours, giant cell lesions and bone cysts, and bone and cartilage tumours. This is the first edition that Essential and Desirable Diagnostic Features were added for each entity, so that the most important clinical, microscopic and/or radiologic features were encapsulated and briefly highlighted. Surgical ciliated cyst was added to the group of odontogenic cysts, adenoid ameloblastoma was a newly recognized benign epithelial odontogenic tumour, and segmental odontomaxillary dysplasia was introduced in the group of fibro-osseous tumours and dysplasia. In addition, rhabdomyosarcoma with TFCP2 rearrangement, was introduced into the group of malignant jawbone tumours. The unique genetic aberrations distinguish it from other types of rhabdomyosarcomas. On the other hand, melanotic neuroectodermal tumour of infancy and osteoid osteoma were deleted from the benign bone and cartilageneous tumours, as was the hematolymphoid tumour of solitary plasmacytoma of bone. We systematically reviewed each entity in this chapter and provided important updated findings for selected topics that can further aid in the diagnostic process for challenging cases, broaden insights on the logic of the present classification, and finally, emphasize the potential that some of the molecular results may have in the near future to set new treatment approaches.