Adenoid ameloblastoma: clinicopathologic description of five cases and systematic review of the current knowledge

The evolving molecular characterisation, histological criteria and nomenclature of adenoid ameloblastoma as a World Health Organisation tumour type

Adenoid ameloblastoma (AA) was recently recognised as a separate tumour type in the most recent World Health Organisation (WHO) classification of head and neck tumours. This decision has been considered controversial by several groups, who have described AA as a subtype of ameloblastoma, a hybrid odontogenic tumour or to fall within the spectrum of other recognised odontogenic tumours, including dentinogenic ghost cell tumour and adenomatoid odontogenic tumour. Here we review the reasons for the WHO decision to classify AA as a separate tumour type. We also critique molecular and histological findings from recent reports published since the WHO classification. While acknowledging that the classification of tumours is constantly evolving, the balance of current evidence suggests that AA should remain a distinct tumour type, and not a subtype of ameloblastoma, pending further molecular characterisation.

Challenging pitfalls in frozen section pathology: a case of mandible ghost cell odontogenic carcinoma and the literature review

BACKGROUND

Ghost cell odontogenic carcinoma (GCOC) is a rare malignancy characterized by the presence of ghost cells, preferably in the maxilla. Only slightly more than 50 case reports of GCOC have been documented to date. Due to the rarity of this tumor and its nonspecific clinical criteria, there is a heightened risk of misdiagnosis in clinical examination, imaging findings, and pathology interpretation.

CASE PRESENTATION

A 50-year-old male patient presented to the hospital due to experiencing pain in his lower front teeth while eating for the past 2 months. Upon examination, a red, hard, painless mass was found in his left lower jaw, measuring approximately 4.0 cm × 3.5 cm. Based on the malignant histological morphology of the tumor and the abundant red-stained keratinized material, the preoperative frozen section pathology misdiagnosed it as squamous cell carcinoma (SCC). The surgical resection specimen pathology via paraffin section revealed that the tumor was characterized by round-like epithelial islands within the fibrous interstitium, accompanied by a large number of ghost cells and some dysplastic dentin with infiltrative growth. The malignant components displayed marked heterogeneity and mitotic activity. Additionally, a calcified cystic tumor component of odontogenic origin was observed. Hemorrhage, necrosis, and calcifications were present, with a foreign body reaction around ghost cells. Immunoreactivity for β-catenin showed strong nuclear positivity in tumor cells, while immunostaining was completely negative for p53. The Ki67 proliferation index was approximately 30-40%. The tumor cells exhibited diffuse CK5/6, p63, and p40 immunoreactivity, with varying immunopositivity for EMA. Furthermore, no BRAFV600E mutation was identified by ARMS-PCR. The final pathology confirmed that the tumor was a mandible GCOC.

CONCLUSION

We have reported and summarized for the first time the specific manifestations of GCOC in frozen section pathology and possible pitfalls in misdiagnosis. We also reviewed and summarized the etiology, pathological features, molecular characteristics, differential diagnosis, imaging features, and current main treatment options for GCOC. Due to its rarity, the diagnosis and treatment of this disease still face certain challenges. A correct understanding of the pathological morphology of GCOC, distinguishing the ghost cells and the secondary stromal reaction around them, is crucial for reducing misdiagnosis rates.

Adenoid ameloblastoma with dentinoid: A rare hybrid odontogenic tumor

BACKGROUND

Adenoid ameloblastoma with dentinoid (AAD) is a hybrid odontogenic tumor comprising histopathological presentation of ameloblastoma (AM) and adenomatoid odontogenic tumor (AOT) along with extracellular dentinoid material.

CASE PRESENTATION

A 35-year-old female reported an asymptomatic swelling in the left mandibular posterior region. Histopathological examination revealed composite features of AM with AOT along with dentinoid material, which stained positively with Van Gieson and trichrome stains.

CONCLUSION

The present case report serves to add further to the modicum of literature reports pertaining to AAD, which may gain recognition as a distinct entity in future World Health Organization (WHO) classification of odontogenic tumors.

Adenoid 'ameloblastoma': Clinicopathological description of 4 additional BRAF-negative cases

OBJECTIVE

Adenoid ameloblastoma (AA) is an epithelial odontogenic tumor that was recognized as a separate entity in the last odontogenic classification of WHO in 2022. The etiology is unknown, and the pathogenesis remains controversial. The objective of this study is to contribute the clinicopathological features of 4 additional BRAF-negative cases to the existing literature, aiming to enhance the molecular understanding of this unique tumor in the forthcoming classification.

MATERIALS AND METHODS

This study consists of a case series of four patients diagnosed with AA. The patients' demographic and clinical information were collected from the universities' medical achieves. Histopathologically, all cases were reexamined according to the latest update of the WHO odontogenic tumor classification. In addition to H&E and immunohistochemical stains, cytogenetics was also evaluated.

RESULTS

Well-defined unilocular radiolucent lesions were observed in all cases. Ameloblastoma-like components exhibited reserved nuclear polarity, suprabasal stellate reticulum-like epithelium, duct-like structure, whorls/morules, and cribriform architecture were common features. Variable immunoreactivity to CK7, CK19, CK14, p63, and p40 were determined, and proliferative activity was greater than 15%. The BRAF molecular study revealed no mutations.

CONCLUSIONS

When diagnosing AA, the essential histopathological characteristics must be rigorously applied, and a significant portion of the lesion should contain these features. Additionally, despite limited molecular data, since the BRAF mutation commonly observed in ameloblastomas is not present in the majority of AA cases, we propose changing the term "ameloblastoma" to "ameloblastic" and referring to it as "adenoid ameloblastic tumor" in the forthcoming classification.

Adenoid Ameloblastoma Shares Clinicopathologic, Immunohistochemical, and Molecular Features With Dentinogenic Ghost Cell Tumor: A Comparative Analysis

The updated classification of odontogenic tumors by the World Health Organization (WHO) has included adenoid ameloblastoma (AA) as a distinct entity. However, distinguishing between AA and dentinogenic ghost cell tumor (DGCT) can still be challenging due to their significant morphologic similarities. In this study, we aimed to compare the clinicopathologic, immunohistochemical, and molecular characteristics of AA and DGCT to aid in their differentiation and to shed light on their pathologic mechanisms. Thirteen cases of AA and 14 cases of DGCT (15 samples) were analyzed, along with 11 cases of adenomatoid odontogenic tumor (AOT) and 18 cases of conventional ameloblastoma (AM) for comparative purposes. The study found that AA and DGCT shared a similar long-term prognosis. Immunohistochemically, all cytokeratins detected, except CK8/18, were not statistically significant in differentiating AA and DGCT, while there was a statistically significant difference in the immunophenotype of CK7 and CK10/13 between AA and AM. Nuclear β-catenin accumulation were detected in all cases of AA and DGCT, while AOTs and AMs exhibited cytoplasmic β-catenin. Molecularly, CTNNB1 hotspot mutations were found in only 1 case of AA (1/13), but not found in the other 3 types of tumors. BRAF p.V600E mutation was positive in 2/13 (15%) AA, 1/15 (7%) DGCT, and 2/11 (18%) AOT cases. In comparison, conventional AM was positive for BRAF p.V600E mutation in 94% (17/18) of cases, while KRAS mutations were detected in 63% (7/11) of AOT cases. The study suggests that the so-called AA is a rare benign tumor that exhibits clinical, immunohistochemical, and molecular features similar to DGCTs. Based on these findings, AA should not be categorized as a standalone entity solely based on the presence of whorls/morules and cribriform/duct-like structures. Further studies are needed to investigate the pathologic mechanisms of these tumors and to identify potential therapeutic targets.

Adenoid Ameloblastoma with BRAF p.V600E Mutation Revealing Ameloblastomatous Origin: A First Case Report

BACKGROUND

Adenoid ameloblastoma (AdAM) is a frequently recurrent tumor that shows hybrid histological features of both ameloblastoma and adenomatoid odontogenic tumor (AOT). AdAM is expected to be classified as a new subtype of ameloblastoma in the next revision of the World Health Organization (WHO) odontogenic tumor classification. However, whether AdAM is a histologic variant of ameloblastoma or AOT remains unclear. To establish a new category, genetic evidence indicating the tumor category is necessary.

METHODS

We present a case of a 23-year-old Japanese woman with AdAM who underwent genetic/DNA analysis for ameloblastoma-related mutation using immunohistochemical staining, Sanger sequencing, and next-generation sequencing (NGS) analyses with reliable clinicopathological evidence.

RESULTS

Immunohistochemical expression of BRAF p.V600E was diffusely positive for both ameloblastoma- and AOT-like components. Sanger sequencing and NGS analyses showed missense mutations in BRAF p.V600E (c.1799T > A), a gene that is commonly altered in ameloblastomas but not in KRAS, another gene associated with AOT.

CONCLUSION

This case report is the first to provide genetic evidence on the ameloblastomatous origin of AdAM with a BRAF p.V600E mutation. A larger series of AdAM groups' molecular testing is needed to aptly classify them and prognosticate the best treatment.

A Systematic Review of Adenoid Ameloblastoma: A Newly Recognized Entity

BACKGROUND

Recently, a new odontogenic tumor has been described, the so-called adenoid ameloblastoma (AdAM). The aim of this review was to determine the clinical and imaging features of AdAM and to describe its main histopathological findings.

METHODS

The systematic review included published cases with a diagnosis of AdAM in the gnathic bones, which had sufficient clinical, imaging, and histopathological data to confirm its diagnosis. The following histopathological diagnostic criteria were adopted: presence of ameloblastoma-like components, duct-like structures, spiral cellular condensations, and a cribriform architecture.

RESULTS

Fifteen articles, corresponding to 30 cases of AdAM, were selected. Most cases affected men (63.3%), with a slight preference for the mandible (16:14) and the posterior region of gnathic bones was the most commonly affected site. The mean age at diagnosis was 40.8 years. Clinically, the lesions usually presented as a swelling (53.3%) and, radiographically, as a well-defined radiolucency (33.4%). Surgical resection (40%) was the most frequently adopted treatment and recurrence occurred in 30% of cases. Microscopic examination showed cribriform areas in most AdAM cases (93.3%); duct-like structures and spiral cellular condensations were seen in 100% of the cases.

CONCLUSION

The small number of reported cases, the existence of erroneous diagnoses, and the adoption of initial conservative management make it difficult to determine whether AdAM has a higher risk of recurrence or more aggressive biological behavior than conventional ameloblastomas.

Dentinogenic ghost cell tumor revisited from a single institution in China with focus on adenoid ameloblastoma-like features

OBJECTIVE

The present study aims to identify adenoid ameloblastoma (AdAM) from previously diagnosed cases of dentinogenic ghost cell tumor (DGCT), and gain insight to the possible relationship between AdAM and DGCT.

METHODS

DGCT cases diagnosed between 2006 and 2022 were re-examined with focus on the AdAM-like features.

RESULTS

A total of nine patients were included. Seven patients were males and two were females. The mean age was 38.0 ± 16.0 years. Five tumors occurred in the maxilla and four in the mandible, with a remarkable predilection for the posterior regions of both jaws. Microscopically, dentinoid material deposition was present in all cases. The ghost cells were absent in two cases. Rare ghost cells (<1%) were observed in three cases, and a higher proportion of ghost cells (5%-20%) were present in the remaining four cases. All cases showed prominent AdAM-like features, including duct-like structures, whorls/morules, and cribriform architecture. According to the diagnostic criteria proposed by the 2022 WHO classification, five cases without or with rare ghost cells were reclassified as AdAM. The other four cases including a higher proportion of ghost cells consisted of a mixture of DGCT and AdAM histopathologic patterns.

CONCLUSION

Our results confirmed that the AdAM-like features had been largely overlooked in the diagnosis of DGCT at our institution in the past. Whilst a subset can now be more accurately classified as AdAM, some tumors showed overlapping morphological features between AdAM and DGCT, suggesting that the two may represent a spectrum of the same entity.

The molecular basis of odontogenic cysts and tumours

The advances in molecular technologies have allowed a better understanding of the molecular basis of odontogenic cysts and tumours. PTCH1 mutations have been reported in a high proportion of odontogenic keratocyst. BRAF p.V600E are recurrent in ameloblastoma and KRAS p.G12V/R in adenomatoid odontogenic tumour, dysregulating the MAPK/ERK pathway. Notably, BRAF p.V600E is also detected in ameloblastic carcinoma, but at a lower frequency than in its benign counterpart ameloblastoma. Recently, adenoid ameloblastoma has been shown to be BRAF wild-type and to harbour CTNNB1 (β-catenin gene) mutations, further suggesting that it is not an ameloblastoma subtype. CTNNB1 mutations also occur in other ghost-cell-containing tumours, including calcifying odontogenic cysts, dentinogenic ghost cell tumours and odontogenic carcinoma with dentinoid, but the link between CTNNB1 mutations and ghost cell formation in these lesions remains unclear. Regarding mixed tumours, BRAF p.V600E has been reported in a subset of ameloblastic fibromas, ameloblastic-fibrodentinomas and fibro-odontomas, in addition to ameloblastic fibrosarcoma. Such mutation-positivity in a subset of samples can be helpful in differentiating some of these lesions from odontoma, which is BRAF-wild-type. Recently, FOS rearrangements have been reported in cementoblastoma, supporting its relationship with osteoblastoma. Collectively, the identification of recurrent mutations in these aforementioned lesions has helped to clarify their molecular basis and to better understand the interrelationships between some tumours, but none of these genetic abnormalities is diagnostic. Since the functional effect of pathogenic mutations is context and tissue-dependent, a clear role for the reported mutations in odontogenic cysts and tumours in their pathogenesis remains to be elucidated.

Adenoid ameloblastoma harbors beta-catenin mutations

Adenoid ameloblastoma is a very rare benign epithelial odontogenic tumor characterized microscopically by epithelium resembling conventional ameloblastoma, with additional duct-like structures, epithelial whorls, and cribriform architecture. Dentinoid deposits, clusters of clear cells, and ghost-cell keratinization may also be present. These tumors do not harbor BRAF or KRAS mutations and their molecular basis appears distinct from conventional ameloblastoma but remains unknown. We assessed CTNNB1 (beta-catenin) exon 3 mutations in a cohort of 11 samples of adenoid ameloblastomas from 9 patients. Two of the 9 patients were female and 7 male and in 7/9 patients the tumors occurred in the maxilla. Tumors of 4 of these 9 patients harbored CTNNB1 mutations, specifically p.Ser33Cys, p.Gly34Arg, and p.Ser37Phe. Notably, for one patient 3 samples were analyzed including the primary tumour and two consecutive recurrences, and results were positive for the mutation in all three tumors. Therefore, 6/11 samples tested positive for the mutation. In the 6 mutation-positive samples, ghost cells were present in only 2/6, indicating beta-catenin mutations are not always revealed by ghost cell formation. Dentinoid matrix deposition was observed in 5/6 mutation-positive samples and clear cells in all 6 cases. None of the cases harbored either BRAF or KRAS mutations. Beta-catenin immunoexpression was assessed in the samples of 8 patients. Except for one wild-type case, all cases showed focal nuclear expression irrespective of the mutational status. Together with the absence of BRAF mutation, the detection of beta-catenin mutation in adenoid ameloblastomas supports its classification as a separate entity, and not as a subtype of ameloblastoma. The presence of this mutation may help in the diagnosis of challenging cases.

The diagnostic utility of BRAF VE1 mutation-specific immunohistochemistry in ameloblastoma

Ameloblastoma is a benign, locally aggressive odontogenic neoplasm with variable solid and cystic morphology. On account of its histologic variety, diagnostically challenging cases can bear resemblance to odontogenic keratocyst/keratocystic odontogenic tumor (KCOT) or dentigerous cyst (DC). BRAF^V600E mutation has been reported to be specific for and frequent in ameloblastoma, and this study evaluated the usefulness of immunohistochemistry (IHC) using the BRAF VE1 mutant-specific antibody as a diagnostic adjunct in this setting. We investigated 46 ameloblastomas, 30 KCOTs, and 30 DCs. BRAF VE1 IHC was performed on all cases and allele-specific polymerase chain reaction (AS-PCR) for BRAF^V600E mutation was performed on 30 ameloblastomas and any IHC-positive KCOT/DC. BRAF VE1 IHC was positive in 31/37 (83.8%) mandibular ameloblastomas but not in any maxillary ameloblastomas (0/9), KCOT (0/30), or DC (0/30). Equivocal staining was seen in 1/37 (3.3%) mandibular ameloblastomas. Of the 30 ameloblastomas subjected to AS-PCR, BRAF^V600E mutation was identified in 19/23 (82.6%) mandibular ameloblastomas and 0/7 (0.0%) maxillary ameloblastomas. BRAF^V600E mutant ameloblastomas were positive by IHC in 18/19 (94.7%) cases and equivocal in 1/19 (5.3%) cases. All 11 (100.0%) BRAF-wild type ameloblastomas were negative by IHC. BRAF VE1 is an excellent tool for the diagnosis of mandibular ameloblastoma but of limited utility in the maxilla, where it less commonly occurs and where BRAF^V600E mutation is considerably less frequent.

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.

Unicystic adenoid ameloblastoma: A new variant?

Adenoid ameloblastoma with dentinoid is an uncommon benign odontogenic neoplasm, and its unicystic variant seems to be even rarer. A 34-year-old man was referred for evaluation of an asymptomatic swelling in the posterior maxilla. Intraoral examination showed an expansive lesion, soft to palpation, covered by a normal color mucosa. Cone beam computed tomography revealed a well-defined unilocular hypodense tumor involving the left maxillary sinus. Histopathological examination of the surgically excised specimen showed a cystic tumor lined by an ameloblastic-like epithelium containing columnar basal cells with hyperchromatic and polarized nuclei. In some areas of the capsule, the tumor showed mural infiltration by sheets of cells containing central whirling structures. Dentinoid material was also observed in association with ameloblastic-like cells. The tumor was BRAF and KRAS wild-type. Collectively, these findings were consistent with the diagnosis of a unicystic variant of adenoid ameloblastoma with dentinoid.

Metatypical Adenoid Cystic Carcinoma: A Variant Showing Prominent Squamous Differentiation With a Predilection for the Sinonasal Tract and Skull Base

Adenoid cystic carcinoma is a malignant salivary gland neoplasm, commonly involving the major and minor salivary glands. Adenoid cystic carcinoma arising in the skull base region is considerably less common and is characterized by aggressive clinical behavior, perineural invasion, and intracranial extension. Classically, these tumors are composed of ductal and myoepithelial cells, arranged as tubules and cribriform structures, as well as in a solid pattern when higher in grade. The distinctive molecular findings in this tumor are the gene fusions involving the MYB/MYBL1 and NFIB genes. Squamous differentiation, trabecular, and macrocystic growth patterns are exceedingly rare in these tumors and when present can cause significant diagnostic challenges. Squamous differentiation, in particular, is considered by many to be an exclusion criterion for adenoid cystic carcinoma outside of cases with high-grade transformation. In addition, a similar-appearing tumor with squamous differentiation, namely human papillomavirus-related multiphenotypic sinonasal carcinoma, has recently been defined, further complicating this differential diagnosis. Recently, we have come across 3 cases of adenoid cystic carcinomas involving the sinonasal tract and skull base having extensive interconnecting trabecular growth, macrocysts, and squamous differentiation, yet demonstrating the signature fusions involving MYB-NFIB and MYBL1-NFIB by RNA sequencing. In this article, we describe the clinical, histomorphologic, and imaging findings of these cases and propose the appellation "metatypical adenoid cystic carcinoma" for this uncommon variant morphology.

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.

Comparative Analysis Between Dentinogenic Ghost Cell Tumor and Ghost Cell Odontogenic Carcinoma: A Systematic Review

Dentinogenic ghost cell tumor (DGCT) and ghost cell odontogenic carcinoma (GCOC) form a spectrum of rare benign and malignant odontogenic neoplasms, respectively. The aim of this study was to perform a comparative systematic review of the clinicopathological, genetic, therapeutic, and prognostic features of DGCT and GCOC. The electronic search was performed until December 2020 on seven electronic databases. Case reports, series, and research studies with enough histopathological criteria for diagnosis and all genomic studies were included. Both DGCT and GCOC showed a male prevalence (p = 0.043), with mandibular and maxillary predilections, respectively (p = 0.008). Peripheral DGCT (DGCTp) affected most elderly people (p < 0.001), and central DGCT (DGCTc) and GCOC occurred mainly in younger individuals. Unilateral enlargement of maxilla or mandible was the most common clinical sign associated with a radiolucent or mixed image. Ameloblastomatous epithelium was often present in both neoplasms. Basaloid and large cells with vesicular nuclei were also frequently seen in GCOC. β-catenin expression and mutations (CTNNB1 gene) were found in DGCT and GCOC. Conservative surgery was mostly used for DGCTp, while radical resection was chosen for DGCTc and GCOC. High recurrence rates were found in DGCTc and GCOC. Metastasis occurred in 16.7% of GCOC cases and the 5-year survival rate was 72.6%. DGCT and GCOC share numerous clinicopathological features and demand a careful histopathological evaluation, considering the overlap features with other odontogenic tumors and the possibility of malignant transformation of DGCT. A strict regular post-operative follow-up is mandatory due to high recurrence rates and metastatic capacity in GCOC.

Adenoid ameloblastoma with dentinoid is molecularly different from ameloblastomas and adenomatoid odontogenic tumors

BACKGROUND

Adenoid ameloblastoma is a rare epithelial neoplasm, histologically characterized by the presence of ameloblastoma-like features, duct-like structures, epithelial whorls, and cribriform architecture. Dentinoid material is usually present. Some advocate adenoid ameloblastoma is an ameloblastoma variant. However, there are overlapping features not only with ameloblastoma, but also with adenomatoid odontogenic tumor. Most ameloblastomas are characterized by the presence of BRAF p.V600E mutations and adenomatoid odontogenic tumors harbor signature KRAS mutations. The molecular features of adenoid ameloblastoma remain unknown.

METHODS

Nine adenoid ameloblastoma cases were screened by TaqMan allele-specific qPCR to assess BRAF p.V600E, ameloblastoma signature mutation, and KRAS p.G12V and p.G12R, adenomatoid odontogenic tumor signature mutations.

RESULTS

BRAF and KRAS mutations were not detected in any of the adenoid ameloblastoma cases.

CONCLUSION

The molecular results support adenoid ameloblastoma as an entity distinct from adenomatoid odontogenic tumor and ameloblastoma.

Dentinogenic ghost cell tumor with focal atypical features suggesting ghost cell odontogenic carcinoma: Report of a challenging diagnosis

Dentinogenic ghost cell tumor (DGCT) represents a rare benign odontogenic neoplasm that can appear in a central or peripheral form and may rarely undergo malignant transformation to ghost cell odontogenic carcinoma (GCOC). We aim to report a case of a central DGCT with focal cytological malignant aspects. A 24-year-old woman exhibited a painful enlargement and dental mobility in the left posterior maxilla for about one year, which appeared as an expansive well-defined hypodense maxillary image with hyperdense foci invading ipsilateral maxillary sinus. Incisional biopsy showed a predominantly solid hyperchromatic basaloid epithelium presenting cellular pleomorphism and mitotic activity, admixed with abundant ghost cell aggregates and dentinoid material. The lesion was immunopositive for p53 and had 21% of Ki-67 proliferation index (PI). These microscopic features suggested initially a GCOC diagnosis. Partial left maxillectomy was performed without complications. The surgical specimen presented an exuberant variation of the epithelial parenchyma, including ameloblastomatous, fusiform, and cribriform areas, with numerous ghost cells and dentinoid material, lacking any signs of malignancy. The final diagnosis was DGCT. The patient is in a strict regular follow-up for over two years, and there are no signs of recurrence.

Diagnostic Enigma of Adenoid Ameloblastoma: Literature Review Based Evidence to Consider It as a New Sub Type of Ameloblastoma

Adenoid ameloblastoma is a hybrid odontogenic tumour showing histopathological features of both ameloblastoma and adenomatoid odontogenic tumour (AOT), with approximately 40 cases reported in the literature. The aims of the report are to illustrate the diagnostic challenges of adenoid ameloblastoma using three new cases and to analyze evidence in literature to consider adenoid ameloblastoma as a new sub type of ameloblastoma. A literature review was performed with the key words-adenoid ameloblastoma, hybrid/composite odontogenic tumours, hybrid ameloblastoma and adenomatoid odontogenic tumour, ameloblastoma with inductive changes, dentinoid and dentinoma to select the cases compatible with the diagnosis of adenoid ameloblastoma. Out of the 40 cases reported in literature, 31 cases with sufficient information and 3 new cases were analyzed. Out of the 34 adenoid ameloblastomas majority of tumours (76.5%) occurred in adults with age ranging from 25 to 55 years. Slight female predilection with a male:female ratio of 0.9:1 was observed. Approximately, 64.7% occurred in the mandible. Radiologically, 82.4% of adenoid ameloblastomas presented as radiolucent lesions while 47.1% occurred with ill-defined margins and cortical perforation at diagnosis. Histopathologically, 70.8% of tumours presented as plexiform ameloblastomas, while duct like structures/glandular structures were the commonest feature supportive of adenomatoid odontogenic tumour observed in overwhelming majority of 95.9% of adenoid ameloblastomas. 91.6% of tumours showed inductive change in the form of dentinoid. Further, 45.4% of the tumours developed at least one recurrence following surgical excision. The report presents literature review based evidence to show the existence of adenoid ameloblastoma, which is demographically similar to conventional ameloblastoma but with histopathological differences and presenting with higher rate/multiple recurrences, indicating its biological aggressiveness. Thus, we would like to propose the inclusion of adenoid ameloblastoma as a sub type of ameloblastoma in the next revision of the WHO odontogenic tumour classification.

Adenoid ameloblastoma in the posterior maxilla: a case report and review of the literature

INTRODUCTION

Adenoid ameloblastoma is a rare benign odontogenic tumor that favors a slight predilection for male patients, fourth and fifth decades of life, and posterior regions of the jaws. To date, less than 40 cases have been reported in the English language literature. The radiographic aspects of adenoid ameloblastoma vary from unilocular and well-defined lesions to diffuse and multilocular lesions. Most of the lesions exhibit a radiolucent image and are usually large, with a mean size of 3.5 cm. Microscopically, pseudoductal structures composed of columnar cells in a palisaded arrangement formed from the parenchyma of the tumor were observed.

CASE PRESENTATION

We describe a case of adenoid ameloblastoma in a 54-year-old woman, who presented with no symptoms. Panoramic radiography showed a well-circumscribed, unilocular radiolucency in the left posterior maxilla.

CONCLUSION

As odontogenic tumors are rare, some entities are infrequently encountered, making the diagnosis more difficult. Clinicians, oral and maxillofacial surgeons and oral pathologists should be familiar with the adenoid ameloblastoma and its differential diagnosis for accurate diagnosis and management.

p16INK4a as a proliferation marker unrelated to HPV expression in odontogenic cysts and tumors

INTRODUCTION

p16INK4a is a tumor suppressor protein that retards cell cycle progression from G1 to S phase. Prior studies have evaluated p16INK4a expression in odontogenic keratocyst and ameloblastoma, but data regarding other odontogenic cysts and tumors have been sparse.

METHODS

With IRB approval, cases from the following entities were identified from archives of the UF Oral Pathology Biopsy Service (2005-2015): benign incidental odontogenic rest, dentigerous cyst, lateral periodontal cyst, calcifying odontogenic cyst, glandular odontogenic cyst, odontogenic keratocyst, orthokeratinized odontogenic cyst, adenomatoid odontogenic tumor, calcifying epithelial odontogenic tumor, and ameloblastoma. All cases were submitted for p16INK4a immunohistochemical testing.

RESULTS

Results were scored as follows: nuclear and cytoplasmic staining of <5% cells (score 0), 5%-25% (score 1), 25%-50% (score 2), >50% (score 3). No significant difference in p16INK4a staining was noted between odontogenic cysts and the listed odontogenic tumors (chi-square, P = .540). When comparing lesions with higher recurrence rates (over 25% as reported in the literature) versus lesions with low recurrence rates (under 25%), higher recurrence correlated to significantly higher p16INK4a positivity (chi-square, P = .001). Follow-up testing was performed on 18 cases with "2" or "3" p16INK4a expression scores for high-risk HPV strains through HPV in situ hybridization (ISH) messenger RNA testing with no cases exhibiting a positive result.

CONCLUSION

This study exhibits an association between increased p16INK4a positivity and odontogenic lesions with higher recurrence rates and highlights the role of p16INK4a as a progression marker unrelated to HPV expression in this group of pathologic entities.

Update on Odontogenic Tumors: Proceedings of the North American Head and Neck Pathology Society

Odontogenic tumors are rare entities, often derived from the epithelial remnants in the gnathic bones following odontogenesis. This brief manuscript will seek to address recent developments pertaining to odontogenic tumors as well as particularly uncommon odontogenic tumors and the difficulties in their diagnosis.

Ameloblastoma with adenoid features: A series of eight cases

BACKGROUND

Ameloblastoma with adenoid features are characterized by the presence of duct-like structures formed from the parenchyma of the tumor. This study was conducted to report a series of eight ameloblastomas with adenoid features, highlighting their clinicopathological and immunohistochemical aspects.

MATERIAL AND METHODS

Out of 71 cases of ameloblastomas, this study classified 8 cases as ameloblastomas with adenoid features. Clinicopathological data and immunohistochemistry for CK7, CK14, CK19, IMP3, p53 and Ki-67 were evaluated.

RESULTS

From those cases of ameloblastoma exhibiting adenoid features, there were 4 women and 4 men, with mean age of 39 years. Most cases affected the mandible and all presented radiographically as a radiolucency. The predominant histopathological features were pseudoducts, squamous metaplasia, nuclear hyperchromatism, clear cells, whorled aspect of epithelial structures, cribriform growth pattern, proliferation of spindle cells and extracellular eosinophilic material. Immunohistochemical analysis showed high expression for CK14 (n = 6) and CK19 (n = 3) and all cases (n = 8) were negative for p53, IMP3 and CK7. In addition, all samples (n = 8) showed low expression for Ki-67.

CONCLUSIONS

The similarities between the histopathological and immunohistochemical features of eight cases described in the present study and those described in previous studies support the possibility that these lesions are adenoid ameloblastomas. In addition, the immunohistochemical results of CK14, CK19, p53 and Ki-67 did not differ from those of conventional ameloblastomas.