Clinical Characterization of Oral and Maxillofacial Tumors and Tumor-Like Lesions in Children and Adolescents.

PURPOSE: To investigate the clinical characteristics of oral and maxillofacial tumors in children and adolescents. METHODS: This is a retrospective study of patients who had oral and maxillofacial tumors under the age of 18 years and were treated at the Department of Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology from January 1990 to July 2021 (31 y). Their general conditions, pathological diagnosis, gender, age, and anatomical location were counted to analyze their morbidity and composition characteristics. RESULTS: This study contained 5405 cases, including 2903 male patients and 2502 female patients, with a median age of 9 years. Peak incidence was observed in the 14 to 18 years age group. The mandible (22.15%), maxilla (11.75%), and tongue (9.25%) were the most common sites of incidence. Malignant and intermediate type tumors accounted for 13.04%, benign tumors and tumor-like lesions for 55.67%, most often occurs in the maxillofacial bone, of which fibro-osseous lesions constitute an important part. Cysts accounted for 31.29%. Among the tumors occurring in the jaws, the most common malignant type was sarcoma, and ameloblastoma was the most common benign tumor. Malignant jaw tumors were mostly treated by resection, 10.64% by fibular flap reconstruction. While benign jaw tumors and tumor-like lesions were mostly treated by resection or curettage. CONCLUSIONS: The distribution of anatomical location and pathological types of oral and maxillofacial tumors in children has certain characteristics, so that the selection of their treatment options is different from that of adults due to the consideration of the growth and developmental characteristics of children.

Brown tumors of the jaw: an atypical manifestation of primary hyperparathyroidism.

Brown tumors represent the terminal stage of bone remodeling processes in primary hyperparathyroidism. Currently they are rare, and typically affect long bones, pelvis and ribs. Brown tumors may be not included in the initial differential diagnosis of bone disease, especially when they are present in atypical localizations. We reported two cases of oral brown tumors as the initial presentation of primary hyperparathyroidism. In the first case, a 44-year-old woman presented a painful and sessile lesion of 4 × 3 cm over the central body of the mandible which progressively increased in 4-month. The second case involved a 23-year-old woman who was referred with a 3-month history of a painful and ulcerated mass of 2 cm arising from left maxilla, episodes of gingival hemorrhage and difficulty of breathing. Both cases were solitary tumors with no evidence of palpable cervical lymphadenopathy. Incisional biopsy of oral tumors resulted in giant cell and primary hyperparathyroidism was confirmed by laboratory tests. After parathyroidectomy, histology confirmed adenoma in both cases. Although this type of clinical presentation has almost disappeared in the recent decades, brown tumors should be considered in the differential diagnosis of bone oral masses.

Los tumores pardos son raros y, por lo general, afectan huesos largos, pelvis y costillas. Pueden no estar incluidos en el diagnóstico diferencial inicial como manifestación de enfermedad esquelética, especialmente cuando se presentan en localizaciones atípicas. Comunicamos dos casos de tumores pardos orales como presentación inicial de hiperparatiroidismo primario. En el primer caso, una mujer de 44 años presentó una lesión dolorosa y sésil de 4 × 3 cm sobre el cuerpo central de la mandíbula que aumentó de tamaño progresivamente en 4 meses. El segundo caso corresponde a una mujer de 23 años que acudió por presentar una masa dolorosa y ulcerada de 2 cm en maxilar izquierdo de 3 meses de evolución, episodios de hemorragia gingival y dificultad para respirar. Todos fueron tumores solitarios sin evidencia de linfadenopatía cervical palpable. La biopsia incisional de los tumores orales resultó en células gigantes, y las pruebas de laboratorio confirmaron el hiperparatiroidismo primario. Tras la paratiroidectomía, la histología confirmó adenoma en ambos casos. Los tumores pardos representan la etapa terminal de los procesos de remodelación ósea en el hiperparatiroidismo primario. Aunque este tipo de presentación clínica casi ha desaparecido en las últimas décadas, los tumores pardos deben ser considerados en el diagnóstico diferencial de las masas óseas orales.

[The new WHO classification of jaw tumours]. / Die neue WHO-Klassifikation der Kiefertumoren.

Maxillofacial tumours cover a broad spectrum of lesions, including neoplasms, hamartomatous changes and developmental disorders. Since the beginning of 2022, a beta version of the 5th edition of the WHO classification for head and neck tumours has been available online, and a print version is expected to be published in mid-2023. From a conceptual point of view, little has been changed compared to the 4th edition; the sort order of lesions is more rigorously arranged according to benign and malignant behaviour and identical tumour types are no longer described redundantly in different chapters depending on their location. The diagnostic criteria are now summarized as "essential" and "desirable", and in addition to the clinical features, imaging is now also incorporated, providing an interdisciplinary approach to the classification. A few new entities are included for the first time. This article gives an overview of the main changes introduced in the new WHO classification with a special emphasis on fibro-osseous lesions of the craniofacial skeleton.

Para This, Fibromin That: The Role of CDC73 in Parathyroid Tumors and Familial Tumor Syndromes.

CDC73 alterations are associated with three main parathyroid lesions according to the World Health Organization (WHO) classification of tumors of the endocrine system. These include hyperparathyroidism-jaw tumor (HPT-JT) syndrome-associated adenomas, atypical parathyroid tumors (APTs), and parathyroid carcinomas (PCs). The loss of nuclear parafibromin expression, which serves as a surrogate marker for the underlying CDC73 alteration, encompasses these tumors under the term parafibromin-deficient parathyroid tumors. They have distinct morphologic features of more abundant eosinophilic cytoplasm with perinuclear clearing surrounding a large nucleus as well as prominent dilated branching "hemangiopericytoma-like" vasculature and a thick capsule as well as variably sized cystic spaces. These tumors include cases that show unequivocal histologic features fulfilling the criteria for PCs with growing data indicating a higher rate of recurrence or metastasis compared with parafibromin intact PCs. More importantly, the loss of parafibromin expression can be used in clinical practice to recognize APTs that fall short of a conclusive diagnosis of PCs, but clinically behave akin to them. Moreover, recognizing these tumors can lead to an underlying germline mutation and a diagnosis of HPT-JT, which impacts long-term treatment and surveillance for patients and close family.

Clinical, Radiographic and Histologic Evaluation of 40 Cystic Oral Lesions in 37 Cats.

Feline cystic oral lesions are uncommon and include odontogenic cysts and cystic odontogenic tumors. Accurate diagnosis requires close collaboration between the clinician's clinical and radiographic findings and the pathologist's histologic interpretations. The odontogenic cysts identified in this series include a periapical cyst, dentigerous cysts and a type of unclassified collateral cyst that appears to be a previously undefined, distinct entity in cats (UCC). Many of the cysts (52%) were unable to be classified due to insufficient diagnostic information, which often related to the associated tooth being unavailable for evaluation. Cystic odontogenic tumors included ameloblastomas, amyloid producing ameloblastomas (APA), and feline inductive odontogenic tumors (FIOT). The purpose of this case series was to assess correlations between clinical and radiographic findings, histopathologic interpretation and signalment to identify common characteristics and provide recommendations for clinicians and pathologists to optimize diagnostic efficiency and accuracy for cystic oral lesions in cats.

A two-generation hyperparathyroidism-jaw tumor (HPT-JT) syndrome family: clinical presentations, pathological characteristics and genetic analysis: a case report.

BACKGROUND: Hyperparathyroidism-Jaw Tumor (HPT-JT) is caused by inactivating germline mutations of CDC73. This hereditary disease can present with a range of symptoms. Jaw ossifying fibroma (OF) is one of the most important clinical presentations, affecting 30% of HPT-JT patients. However, OF is easily confused with other fibro-osseous lesions (FOLs) of the jaw. The correct diagnosis of HPT-JT is a real challenge and must be confirmed by genetic testing. CASE PRESENTATION: A female proband and her father suffered from multiple and recurrent FOLs in the jaw. Considering well demarcated margin and heterogeneous calcified substance lying in a variable density of fibrous stroma, we reached the diagnosis of jaw OF through radiologic and microscopic analyses. Additionally, the proband presented with chronic anemia resulting from menorrhagia, as well as renal mixed epithelial and stromal tumor (MEST). Two patients both presented with no evidence of Hyperparathyroidism (HPT). A germline start codon mutation (c.1A > G) of CDC73 was identified in them. Copy number loss at the CDC73 gene locus was verified in the jaw tumor sample of the proband. CONCLUSION: Regardless of whether HPT manifestations are present, patients with heritable jaw OF may be at risk for HPT-JT. Genetic testing should be adopted to confirm the diagnosis. Early recognition of HPT-JT helps to better develop tailored treatment plans and surveillance programs.

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.

[Adenomatoid odontogenic tumor: about two cases]. / La tumeur adénomatoïde odontogène: à propos de deux observations.

Adenomatoid odontogenic tumor is a benign epithelial tumor which mainly affects young women. It usually occurs in the anterior portion of the upper jaw. Diagnosis can be clinically suspected in patients with cyst formation associated with retained tooth but histopathological confirmation is required. This study involved two patients aged 13 and 37 years, with no previous history, presenting after the occurrence of a swelling on the jaw and mandible. Anatomopathological examination of these lesions showed adenomatoid odontogenic tumor. This study highlights the anatomoclinical features, outcome and treatment of this type of tumor.

Cell Block and Its Impact in the Diagnosis of Jaw Lesions over Fine Needle Aspiration Cytology.

OBJECTIVES: To determine the role and efficacy of fine needle aspiration cytology (FNAC) and cell block in diagnosis of jaw lesions and compare the agreement between FNAC and cell block to predict the diagnosis. METHOD: The sample comprised 51 cases, including 12 odontogenic keratocysts (OKCs), 8 ameloblastomas, 22 radicular cysts, 7 dentigerous cysts, and 1 each of intraosseous mucoepidermoid carcinoma (MEC) and adenomatoid odontogenic tumor (AOT). FNAC samples remaining after hematoxylin and eosin (H&E)-stained cytosmear diagnosis were centrifuged at 3,000 rpm for 10 min. The supernatant was discarded and sediment mixed with 2-3 mL alcohol and filtered. To this, 10% formalin was added, filtered, taken for routine processing, and stained with H&E. The result of FNAC smear and cell block was compared with histopathological diagnosis. RESULTS: On cytological examination of the smears, 7 OKCs and 22 radicular cysts were diagnosed, whereas ameloblastomas, AOT, intraosseous MEC, and dentigerous cysts were not. This gave an agreement of 56.8% with the biopsy reports. Cell block sections stained with H&E of 12 OKCs, 22 radicular cysts, 1 MEC, and 3 cases of ameloblastoma offered a diagnosis in accordance with the biopsies giving an agreement of 74.5%, while dentigerous cyst and AOT failed to do so. In comparison with FNAC, additionally 5 cases of OKC and 1 of MEC could be detected, and in ameloblastoma, out of 8 cases, only 3 yielded a concordant diagnosis through the cell block technique. CONCLUSION: In comparison with FNAC, the architectural pattern and the morphology of the cells were better preserved by the cell block technique. This substantiates that cell block could be used as an ancillary technique to aid in definitive diagnosis of head and neck swellings.

Report of a Rare Case of Spindle Cell Ameloblastic Carcinoma and the Diagnostic Utility of Immunohistochemistry.

Ameloblastic carcinoma is a rare aggressive malignant epithelial odontogenic tumor. The spindle cell variant of ameloblastic carcinoma (SCAC) is exceedingly rare with 15 cases of SCAC having been reported. Therefore, because of the paucity of cases in literature related to SCAC, the biological behavior of the entity has not been well evaluated. Herein the authors report a case of incidentally diagnosed SCAC in a 20-year-old woman identified on imaging as part of the evaluation of a work-related facial injury. Histologically, the tumor had background of cystic ameloblastoma with areas of dense hypercellular spindle cells with short-to-long intersecting fascicles and occasional herringbone pattern intermixed with solid epithelial nests. Both the epithelial and spindle cells were positive for cytokeratin including cytokeratin 19, D2-40, and transducin-like enhancer of split proteins-1 immunohistochemical stains. The patient was followed for 18 months with no evidence of recurrence or metastasis. To the knowledge this is a first case of reporting D2-40 positivity in spindle ameloblastic carcinoma and this immunostain could be used as helpful marker to diagnose this entity.

A clinicopathologic analysis of 135 cases of cemento-osseous dysplasia: To operate or not to operate?

PURPOSE: The aim of this retrospective study was to investigate the characteristics of cemento-osseous dysplasia (COD) lesions for devising a clinical algorithm to help management decisions, specifically discussing the need for a possible surgical intervention versus solely follow-up. MATERIALS AND METHODS: One hundred thirty-five subjects were thus identified having previously diagnosed and treated for COD from the archives of the pathology in between 2005-2015. These were then re-evaluated. Demographic features, radiographic and histopathologic findings were assessed. RESULTS: The most frequent variant was the focal type (n=83), and the mandible (n=131) was predominantly affected jaw bone. Female predilection was evident for all subtypes. Almost half of the lesions (n=72) presented with mixed radiolucent and radiopaque appearances in radiography at the time of the biopsy. Cementicles/psammoma body-like calcifications and trabecular pattern were the most common hard tissue appearances. CONCLUSION: COD lesions are non-neoplastic fibro-osseous lesions which can exhibit similar histopathologic and radiologic features with other bone lesions. Ideally, these lesions should be clinically identified and followed-up. Considering the possible complications, a thorough knowledge of these lesions and their differentials is essential in order to avoid unnecessary surgical interventions.

Ameloblastoma diagnosis by fine-needle aspiration cytology supplemented by cell block samples.

Ameloblastomas are rarely encountered in clinical practice, accounting for only 1% of tumors and cysts of the jaw although they are one of the most common odontogenic neoplasms. The cytological features are described in a few case reports only. The aim of this study was to describe the morphological features of ameloblastoma in fine-needle aspiration cytology (FNAC) and highlight the contribution of cell blocks in their diagnosis. Three cases of ameloblastoma diagnosed on FNAC (FNAC) with cell block samples were retrieved and evaluated in detail. Radiological correlation was performed in three cases. Follow-up histopathology of the resected specimen was available in two cases. Cytology smears showed clusters of basaloid cells with high nucleocytoplasmic(N/C) ratio and dense chromatin. Focal squamoid differentiation was present in one case and cystic change predominated in one case. The characteristic morphology of the tumor was better appreciated on cell block section with cribriform and trabecular arrangement of tumor cells with peripheral nuclear palisading with foci of squamoid differentiation and cystic change. Cell blocks from aspirates act as mini-biopsies and contribute to accurate diagnoses of ameloblastomas of the mandible, thereby emphasizing their contribution to the proper management of these uncommon neoplasms.

Fibula osteal flap with proximal peroneal perforator skin paddle for composite oromandibular reconstruction: A case report.

RATIONALE: Cutaneous perforators of peroneal vessels are divided into proximal and distal perforators on the basis of perforator distributions and musculocutaneous or septocutaneous properties. The traditional fibular osteocutaneous free flap is raised over the distal two-thirds of the fibula with a skin paddle based on distal perforators, which is affixed to the posterior crural septum. However, the skin pedicle may not be available due to anatomic variations or intraoperative injuries. Herein, because of the absence of distal perforators, we reserved and expropriated proximal perforators originating from the musculocutaneous branch of the superior part of the peroneal artery before it divided into nutrient and arcuate arteries and successfully harvested a separate osteal fibula and proximal perforator skin paddle with a single vascular pedicle-peroneal vessel. PATIENT CONCERNS: A 62-year-old man with a 6-month history of mandibular swelling and soft tissue invasion was referred to us. DIAGNOSIS: Panoramic radiography and computed tomography showed an irregular radiolucent lesion of the mandibular body, and histopathological analysis confirmed a follicular-pattern ameloblastoma. INTERVENTIONS: The diseased mandible and soft tissue were resected and reconstructed with a vascularized fibular osteal flap with the proximal perforator skin paddle. OUTCOMES: The mandibular contour was successfully restored; the skin paddle in the mouth was in good condition after 8 months of follow-up. LESSONS: The proximal perforator is reliable and practical for supplying a skin paddle and has significant potential for future applications. We recommend reserving the proximal perforator skin paddle as a backup flap when planning to raise a fibula flap, since unavailability or injury of the traditional fibular skin island based on distal perforators occurs frequently. This approach can avoid the exploration for a second donor site, save surgical time, and reduce surgical complexity. Moreover, we anticipate more frequent use of the proximal perforator flap in the future because of its flexibility and large volume, and since it can be combined with the osteal fibula or fibular osteocutaneous flap. However, an understanding of the traits of the proximal perforator and determination of its peroneal origin by computed tomography angiography is crucial for predesigning fibular osteal flaps with a proximal perforator skin paddle.

Professional diagnostic delay in osteosarcomas of the jaws

A series of 20 consecutive patients with an osteosarcoma of the jaws has been evaluated with regard to possible professional diagnostic delay. When set at an arbitrarily chosen period beyond three months, professional delay occurred in 15 patients, the mean being 21 months and the median 11 months. In five of the 15 patients a wrong diagnosis has been rendered on the biopsy specimen, being fibrous dysplasia (2x), osteoma (2x) and, in case of palatomaxillary swelling, pleomorphic adenoma (1x). In the other ten patients the initial clinicoradiographic features were misleading and apparently not indicative of a malignancy, except for one patient in whom a distinct widening of the periodontal ligament, as expressed on a periapical film, has been overlooked or not properly interpreted. It has not been possible to assess the possible influence of the delayed diagnosis on the prognosis

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Primordial odontogenic tumor: A systematic review

BACKGROUND: The primordial odontogenic tumor (POT) is a recently described benign entity with histopathological and immunohistochemical features suggesting its origin during early odontogenesis. AIM: To integrate the available data published on POT into a comprehensive analysis to better define its clinicopathological and molecular features. MATERIAL AND METHODS: An electronic systematic review was performed up to September 2019 in multiple databases. RESULTS: A total of 13 publications were included, representing 16 reported cases and 3 molecular studies. The mean age of the affected patients was 11.6 years (range 2-19), with a slight predominance in males (56.25%). The posterior mandible was the main location (87.5%), with only two cases affecting the posterior maxilla. All cases appeared as a radiolucent lesion in close relationship to an unerupted tooth. Recurrences have not been reported to date. Microscopically, POT comprises fibromyxoid tissue with variable cellularity surrounded by a cuboidal to columnar odontogenic epithelium but without unequivocal dental hard tissue formation. A delicate fibrous capsule surrounds (at least partially) the tumor. The epithelial component shows immunohistochemical positivity for am-elogenin, CK19, and CK14, and variable expression of Glut-1, Galectin-3 and Caveolin-1, Vimentin, p-53, PITX2, Bcl-2, Bax and Survivin; the mesenchymal tissue is positive for Vimentin, CD90, p-53, PITX2, Bcl-2, Bax, and Survivin, and the subepithelial region exhibits the strong expression of Syndecan-1 and CD34. The Ki-67 index is low (<5%). The negative or weak expression of dentinogenesis-associated genes could explain the inhibition of dentin and subsequent enamel formation in this neoplasm. CONCLUSION: POT is an entity with a well-defined clinicopathological, immunohistochemical and molecular profile that must be properly diagnosed and differentiated from other odontogenic lesions and treated consequently

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Odontogenic Myxoma: Systematic review and bias analysis.

BACKGROUND: Odontogenic myxoma (OM) is a rare neoplasm, which originates from odontogenic ectomesenchyme. There is no study in the literature that analyses the best standards for OM diagnosis and how the treatment modalities may influence the recurrence rates. OBJECTIVE: To evaluate the best standards for odontogenic myxoma (OM) diagnosis and treatment, and how these may influence the recurrence rates. STUDY DESIGN: Two independent researchers performed a systematic review in many databases. Fifty-two eligible studies were included for qualitative analysis. Bias analysis was conducted according to Oxford Centre for Evidence-Based Medicine. RESULTS: A total of 1363 OM cases were reported on, and female gender with average age of 27 years is the most common patient profile. Conventional microscopic findings were observed in 93.43% of the reported cases. In 57.49% of the cases, multilocular radiographic appearance was present, followed by unilocular appearance (32.87%). Posterior mandible was the site with the major prevalence, while surgical resection was the most common treatment modality, followed by enucleation. Recurrence rates for both treatment modalities were approximately close (13.04% and 25.0%, respectively). CONCLUSION: The correct diagnosis of OM relies on the association of clinical, radiographic and microscopic findings. About imaging examinations, panoramic radiography and computed tomography are sufficient for the evaluation of OM. Recurrence rates were closely among the two most used surgery treatments. So according to some clinical-radiological aspects, conservative surgery may be preferred than aggressive surgery modalities.

Diagnostic capability of fine-needle aspiration cytology in assessment of intraosseous lesions of the jaws: A systematic review.

PURPOSE: To systematically review (SR) and critically appraise studies that investigated the diagnostic capability of fine-needle aspiration cytology (FNAC) in the assessment of intraosseous lesions of the jaws. METHODS: Six main electronic databases and three gray literature databases were searched aiming diagnostic studies, which were selected in a two-phase process. Risk of bias (RoB) of included studies was assessed using the Revised Tool for the Quality Assessment of Diagnostic Accuracy Studies. RESULTS: A total of eight articles were included, of which six evaluated the FNAC smear technique exclusively, one assessed both smear and cell-block techniques, while one investigated only the cell-block technique. With regard to the FNAC smear technique, from 134 benign lesions investigated, concordance with the histopathological diagnosis was achieved in 64.17% of cases. In addition, considering the 32 malignant lesions assessed through this technique, concordance with histopathology was achieved in all cases. Regarding the cell-block technique, only benign lesions (n = 40) were evaluated in the included studies, in which the concordance rate with histopathology was of 77.5%. The overall RoB judgment was "at risk of bias" for seven included studies mostly due to lack of information or reportedly absence of blinding of evaluator. CONCLUSIONS: Within the limitations of this SR, FNAC presented modest to satisfactory diagnostic capability for the assessment of intraosseous jaw lesions, showing concordance rates higher than 64% for the smear and 77% for the cell-block technique. Also, considerably high concordance rates were found for the assessment of malignant lesions regarding FNAC smear technique.

The most frequent and/or important lesions that affect the face and the jaws.

INTRODUCTION: The radiology of the most important and/or frequent lesions affecting the bones of the face and jaws has been set out in this review and pictorial essay. METHODS: The latter is composed of multiple images displaying one or more key radiological features derived from almost every one of the most important and/ or frequent lesion affecting the face and the jaws. These images have been grouped together in 18 figures, each served by a detailed and free-standing legend. These lesions are outlined in a flowchart, which focuses on one or at most two radiological features in turn. RESULTS: It begins with those lesions that could indicate systemic disease, such as multiple lesions, and then proceeds onward to single lesions. The first of these single lesions are the neoplasms which need not only an early diagnosis, but also complete ablation in the majority of cases. Cystic lesions are then next, including consideration of the frequently occurring non-cysts such as simple bone cysts and lingual bone defects which require no treatment. Finally, it ends with the periapical radiolucency of inflammatory origin. CONCLUSION: The most important and/or frequent lesions affecting the bones of the face and jaws that present to the oral and maxillofacial clinician can be considered systematically en route to the 'periapical radiolucency of inflammatory origin,' which is one of the most usually encountered lesions in clinical dentistry.

A multi-centre evaluation of malignant odontogenic tumours in Nigeria.

INTRODUCTION: odontogenic tumors originate from neoplastic transformation of the remnants of tooth forming apparatus. There are varying degrees of inductive interactions between odontogenic ectomesenchyme and epithelium during odontogenesis, leading to lesions that vary from benign to malignant. Malignant odontogenic tumours (MOTs) are very rare and are classified according to embryonic tissue of origin. Recently, there has been a few changes to the classification of MOTs according to the World Health Organization's (WHO) classification in 2017. This study aims to evaluate and reclassify MOTs, using a multi-centre approach in some major tertiary dental hospitals in Nigeria. METHODS: this study reviewed the clinicopathological data on 63 cases of MOT diagnosed over 25 years in five major tertiary dental hospitals in Nigeria. All MOT cases were reclassified according to the recent revision to the 2017 WHO classification of odontogenic tumours. RESULTS: from a total of 10,446 biopsies of oral and jaw lesions seen at the 5 study centres over the 25-year study period, 2199 (21.05%) cases were found to be odontogenic tumours (OTs), of which 63 were MOT. MOTs constituted 0.60% of the total biopsy cases and 2.86% of OTs. Odontogenic carcinomas presented with a mean age higher than odontogenic sarcomas. According to our 2017 WHO reclassification of MOTs, odontogenic carcinomas, ameloblastic carcinomas and primary intraosseous carcinomas were found to be the top three lesions, respectively. Carcinosarcomas were found to be extremely rare. CONCLUSION: using a multi-centre approach is a robust way to reduce diagnostic challenges associated with rare maxillofacial lesions such as MOTs.