Clear cell odontogenic carcinomas show EWSR1 rearrangements: a novel finding and a biological link to salivary clear cell carcinomas

Carcinomas with clear cell features and EWSR1 rearrangements: a report of 3 cases

Salivary gland and odontogenic neoplasms with extensive clear cell change are rare lesions but have been increasingly characterized over the past decade. Among this heterogeneous group of neoplasms, hyalinizing clear cell carcinoma (HCCC), clear cell odontogenic carcinoma (CCOC), and clear cell myoepithelial carcinoma (CCMC) share a monophasic clear cell morphology and an EWSR1 gene rearrangement. While HCCC is relatively well characterized, there are a limited number of EWSR1-reaarranged CCMC of salivary glands reported, and its clinicopathologic features in relation to HCCC and nonclear cell myoepithelial carcinoma (MC) have not been clarified. This report describes the clinical, morphologic, and immunophenotypic features of 3 carcinomas composed predominantly of clear cells and with EWSR1 rearrangements by fluorescence in situ hybridization. A comparative literature analysis suggests that HCCC, CCMC, and nonclear cell MC of salivary glands are clinically, histopathologically, and molecularly distinct.

Odontogenic carcinoma with dentinoid: case report and literature review of a rare entity

BACKGROUND

Odontogenic carcinoma with dentinoid (OCD) is a rare and controversial entity, which has not yet been included in the current World Health Organization classification of odontogenic lesions. Owing to the small number of reported cases, the clinicopathological characteristics, biological behavior, prognosis, and appropriate treatment strategies for OCD remain to be defined. Herein, we present an additional case of OCD with a focus on the differential diagnosis and review of the pertinent literature, in order to enable better recognition by oral clinicians and pathologists and further characterization of this entity.

CASE PRESENTATION

This paper reports a case of OCD in the posterior mandible of a 22-year-old female. Radiography showed a well-defined unilocular radiolucency with radiopaque materials. The intraoperative frozen section pathology gave a non-committed diagnosis of odontogenic neoplasm with uncertain malignant potential. Then a partial mandibulectomy with free iliac crest bone graft and titanium implants was performed. Microscopically, the tumor consisted of sheets, islands, and cords of round to polygonal epithelial cells associated with an abundant dentinoid matrix. Immunohistochemically, the tumor cells were diffusely positive for CK19, p63, and β-catenin (cytoplasmic and nuclear). No rearrangement of the EWSR1 gene was detected. The final diagnosis was OCD. There has been no evidence of recurrence or metastasis for 58 months after surgery. We also provide a literature review of OCD cases, including one case previously reported as ghost cell odontogenic carcinoma from our hospital.

CONCLUSIONS

OCD is a locally aggressive low grade malignancy without apparent metastatic potential. Wide surgical excision with clear margins and long-term period follow-up to identify any possible recurrence or metastases are recommended. Histopathological examination is essential to conclude the diagnosis. Special care must be taken to distinguish OCD from ghost cell odontogenic carcinoma and clear cell odontogenic carcinoma, as misdiagnosis might lead to unnecessary overtreatment. Study of additional cases is required to further characterize the clinicopathological features and clarify the nosologic status and biological behavior of this tumor.

Diagnostic Utility of EWSR1 in Clear Cell Odontogenic Carcinoma: A Systematic Review

In the 2022, World Health Organisation classification of odontogenic tumours, the clear cell odontogenic carcinoma is designated as a malignant odontogenic tumour with high recurrence and aggressive behaviour. Deceptive behaviour in the context of a wide range of differentials presents a significant diagnostic problem. It is the fifth most commom type of malignant odontogenic tumor. A systematic assessment of published cases, case series, and retrospective investigations of diagnostic significance of EWSR1 gene in clear cell odontogenic carcinoma is presented to determine trends in presentation, diagnostic characteristics, treatment, and patient outcome. To locate papers reporting clear cell odontogenic carcinoma and EWSR1, extensive database searches were carried out. Demographics, tumour location, immunohistochemical and molecular tests, treatment, follow-up, and recurrence were the variables. 34 cases were detected; 52.9% (n = 18) of the cases were females. The average age was 62.5 years, with a range of 43-82 years. The average size ranged from 3.4 to 8 cm. The mandibular body was the most common location, followed by the maxilla. Maximum immunohistochemistry positivity revealed by CK 19, CKAE1/3, EMA and p63. Most common gene fusion detected was EWSR1-ATF1 in 62.4% of cases contributing to its diagnostic attributes. Surgical treatment was used in 97% of cases. The average follow-up period was 30.3 months, and recurrence was reported in 52.4% of the cases. CCOC can metastasize, and the prognosis is fair. This is first systematic review, where we have attempted to consolidate the mutational expression of EWSR1 in Clear cell odontogenic carcinoma. It is difficult to identify from other clear cell tumours of the head and neck region. It is crucial to distinguish it from other clear cell lesions because of its aggressiveness.

Back to the future! Selected bone and soft tissue neoplasms with shared genetic alterations but differing morphological and immunohistochemical phenotypes

Bone and soft tissue tumors (BST) are a highly heterogeneous group largely classified by their line of differentiation, based on their resemblance to their normal counterpart in adult tissue. Yet, rendering a specific diagnosis can be challenging, primarily due to their rarity and overlapping histopathologic features or clinical presentations. Over the past few decades, seemingly histogenetic-specific gene fusions/translocations and amplifications have been discovered, aiding in a more nuanced classification, leading to well-established objective diagnostic criteria and the development of specific surrogate ancillary tests targeting these genetic aberrations (e.g., immunohistochemistry). Ironically, the same research also has revealed that some specific tumor subtypes may be the result of differing and often multiple gene fusions/translocations, but, more interestingly, identical gene fusions may be present in more than one phenotypically and biologically distinct neoplasm, sometimes with entirely different clinical behavior. Prime examples include, EWSR1::ATF1 and, less commonly, EWSR1::CREB1 gene fusions present in both clear cell sarcoma, a malignant high-grade tumor with melanocytic differentiation, and angiomatoid fibrous histiocytoma, a mesenchymal neoplasm of intermediate malignancy with a generally indolent course. Similarly, MDM2 amplification, once deemed to be pathognomonic for atypical lipomatous tumor/well differentiated and dedifferentiated liposarcoma, has been documented in a range of additional distinct tumors, including low grade osteosarcomas (e.g. low grade central and surface parosteal) and high-grade intimal sarcomas, amongst others. Such findings reinforce the importance of careful attention to morphological and clinicoradiological features and correlation with molecular testing before rendering a specific diagnosis. Future classification systems in BST neoplasms cannot be solely based on molecular events and ideally will balance morphologic features with molecular analysis. Herein, we provide a narrative literature review of the more common BST neoplasms with shared genetic events but differing demographics, morphology, immunophenotype, and clinical behavior, re-emphasizing the importance of the hematoxylin and eosin slide and the "eye" of the practicing pathologist.

Case of metastatic clear cell odontogenic carcinoma with response to chemoimmunotherapy

Our patient initially presented with 6 months of left jaw pain and gingival bleeding, leading to the discovery of a radiolucent left maxillary mass on dental evaluation. A biopsy confirmed clear cell odontogenic carcinoma, and the patient was treated with definitive surgery and radiation for localised disease. Unfortunately, the patient was found to have pulmonary metastases 3 months after initial management and was subsequently treated with a combination of cytotoxic chemotherapy and immunotherapy with a partial response. To our knowledge, this is the first case demonstrating the successful use of chemoimmunotherapy in metastatic clear cell odontogenic carcinoma.

A Comparison of Clear Cell Sarcoma to Jaw and Salivary Tumors Bearing EWS Fusions

OBJECTIVE

To review tumors identified as "clear cell sarcoma" in order to determine similarities to the rare EWS fusion positive jaw and salivary gland tumors clear cell odontogenic carcinoma (CCOC) and clear cell carcinoma of the salivary gland (CCC).

METHODS

PubMed was used to collect all reports of clear cell sarcoma (CCS). Search parameters were "clear cell sarcoma" and "CCS." References in the publications were screened and cross-referenced. Data extracted included demographic characteristics, presenting signs and symptoms, radiographic findings, histological and immunohistochemical features and known molecular/genetic aberrations.

RESULTS

Clear cell sarcoma has several similarities to CCOC and CCC. All three tumor types have similar histologic appearances including the presence of clear cells, as well as similar genetic profiles in that all harbor an EWSR1-CREB family fusions. Additionally, these tumors appear in soft tissue as well as bone, and can have a prolonged clinical course. CCS can appear anywhere in the body, including the head and neck region. All three tumors appear to have a predilection to women, although CCS may have a slight younger age of onset as compared to CCOC and CCC (3rd vs 5th decade of life, respectively).

CONCLUSION

Gaining a better understanding of the similarities and differences between these three tumors may lead to a better understanding of each one.

[Fusion genes in salivary gland tumors]

Salivary gland tumors represent a diagnostic challenge for pathologists due to their rarity, their very wide histopathological and immuno-phenotypic spectrum, and the recent identification of new entities. This article presents the main molecular characteristics of these tumors in order to allow any pathologist to perceive the diagnostic tracks of these ENT tumors and to better guide the molecular approach to establish the diagnosis and guide therapy.

Clear Cell Odontogenic Carcinoma: A Rare JAW Tumor-A Case Report and Literature Review

Clear cell odontogenic carcinoma (CCOC) is a rare epithelial malignant odontogenic tumor of the jaw with a distinct histology and deceptive behavior. As the clinical presentation is often misleading, the contribution of biopsy, molecular biology, immunohistochemistry and cytogenetics are essential in the diagnostic process. This article describes the presentation of an aymptomatic, painless swelling in the lower jaw of a 63 yrs old female, who was initially diagnosed as an ameloblastoma, taken up for segmental resection, subsequently histopathologically diagnosed as a case of clear cell odontogenic carcinoma and later managed with chemotherapy. Current management protocols and presentation of CCOC have also been reviewed.

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.

Detection of salivary gland and sinonasal fusions by a next-generation sequencing based, ligation-dependent, multiplex RT-PCR assay

AIMS

The discovery of tumour type-specific gene fusion oncogenes in benign and malignant salivary gland and sinonasal (SGSN) tumours has significantly increased our knowledge about their molecular pathology and classification.

METHODS AND RESULTS

We developed a new targeted multiplexed next-generation sequencing (NGS)-based method that utilizes ligation dependent reverse-transcriptase polymerase chain reaction (LD-RT-PCR) to detect oncogenic fusion transcripts involving 116 genes, leading to 96 gene fusions known to be recurrently rearranged in these tumours. In all, 180 SGSN tumours (formalin-fixed, paraffin-embedded samples, 141 specimens and 39 core needle biopsies) from the REFCORpath (French network for rare head and neck cancers) with previously identified fusion genes by fluorescent in situ hybridisation (FISH), RT-PCR, or molecular immunohistochemistry were selected to test its specificity and sensitivity and validate its diagnostic use. Tested tumours encompassed 14 major tumours types, including secretory carcinoma, mucoepidermoid carcinoma, adenoid cystic carcinoma, salivary gland intraductal carcinoma, clear cell carcinoma, pleomorphic adenoma, adamantinoma-like Ewing Sarcoma, EWSR1::COLCA2 sinonasal sarcoma, DEK::AFF2 sinonasal carcinoma, and biphenotypic sinonasal sarcoma. In-frame fusion transcripts were detected in 97.8% of cases (176/180). Gene fusion assay results correlated with conventional techniques (immunohistochemistry [IHC], FISH, and RT-PCR) in 176/180 tumours (97.8%).

CONCLUSION

This targeted multiplexed NGS-based LD-RT-PCR method is a robust, highly sensitive method for the detection of recurrent gene fusions from routine clinical SGSN tumours. It can be easily customized to cover new fusions. These results are promising for implementing an integrated NGS system to rapidly detect genetic aberrations, facilitating accurate, genomics-based diagnoses, and accelerate time to precision therapies in SGSN tumours.

Primary Pulmonary Hyalinizing Clear Cell Carcinoma: Case Series With Review of Literature

Background: Hyalinizing clear cell carcinomas of tracheobronchial origin are very rare salivary gland type tumors accounting for less than 1% of lung tumors with only 13 cases reported to date. Their radiological features, morphological spectrum, and molecular features are not well described. Aim: To perform a clinicopathological analysis of primary pulmonary hyalinizing clear cell carcinomas. Method: A retrospective search of primary pulmonary hyalinizing clear cell carcinomas was conducted from authors' institutions and the clinicopathological features including details of molecular testing were analyzed. Results: Five primary pulmonary hyalinizing clear cell carcinomas were identified. The mean patient age at diagnosis was 48.2 years (range: 33-64 years). Three patients were women. All patients were nonsmokers and 3 were symptomatic; 2 were detected incidentally during health screening. The tumors were located in the main lobar bronchi ranging from 1.3 to 4.9 cm in maximum dimension. Microscopy showed cords and nests of at least, focally clear tumor cells. Mucin cysts lacking goblet cells were seen. All tumors were uniformly positive for p40, p63, AE1/AE3, keratin 7, and epithelial membrane antigen but negative for TTF1, KIT, neuroendocrine markers, and other myoepithelial markers. All cases showed Ewing sarcoma breakpoint region 1 (EWSR1) gene rearrangement. Perineural invasion and lymph node metastases were detected in patient 5. Two patients with available follow-up data were recurrence-free until 4 years (patient 1) and 9 months (patient 5) after resection. Conclusion: The present series adds to the scant available literature on primary pulmonary hyalinizing clear cell carcinomas highlighting the characteristic histomorphology, immunoprofiles, and benign outcomes of these rare tumors.

Clinical and Histopathologic Analyses of Nasopharyngeal Hyalinizing Clear Cell Carcinoma: A Series of 26 Cases With Molecular Confirmation

The aim of this study was to evaluate the clinicopathologic features, molecular characteristics, treatment strategy, and prognosis of nasopharyngeal hyalinizing clear cell carcinoma (HCCC). Retrospective observational case series. Institutional pathology records between 2006 and 2022 were searched for all cases of nasopharyngeal HCCC. We included 10 male and 16 female patients aged 30 to 82 years (median: 60.5 y, mean: 54.6 y). The most common symptoms were blood-stained rhinorrhea and nasal obstruction. Tumors most often involved the lateral wall of the nasopharynx, followed by the superior posterior wall. Microscopically, all tumor cells were arranged in sheets, nests, cords, and single cells in a hyaline/myxoid/fibrous stroma. The tumor cells were polygonal, with or without distinct cell borders, and displayed abundant clear-to-eosinophilic cytoplasm. All 26 cases were positive for pancytokeratin, CK7, p40, and p63 but negative for myoepithelial differentiation markers. Ki-67 labeling was low and ranged from 1% to 10%. All 26 cases demonstrated EWSR1 and EWSR1-ATF1 rearrangements, and no case demonstrated MAML2 rearrangement. Complete follow-up data were available for 23 patients: 14 patients underwent endoscopic surgery alone, 5 underwent radiation therapy followed by endoscopic surgery, 3 underwent radiation therapy followed by biopsy, and 1 underwent cisplatin chemotherapy before endoscopic surgery. Clinical follow-up ranged from 6 to 195 months; 13 patients (56.5%) were alive without tumor, 5 patients (21.7%) died of disease, 5 patients (21.7%) survived with tumor. HCCCs of the nasopharynx are rare tumors. The definitive diagnosis depends on histopathology, immunohistochemistry, and molecular studies. The optimal treatment for patients with nasopharyngeal HCCC is wide local excision. Radiation and chemotherapy might be good options for managing locally advanced cases. Nasopharyngeal HCCC is less indolent than previously thought. Tumor stage and the choice of treatment are key factors affecting the prognosis of nasopharyngeal HCCC patients.

Exuberant clear cell odontogenic carcinoma of the mandible harboring EWSR1 rearrangement: Report of a rare case and a literature review

Clear cell odontogenic carcinoma (CCOC) is a rare malignant odontogenic tumour (MOT) that mainly affects the mandible, with a slight female predominance in adult patients. In this study, we described an exuberant CCOC in mandible of a 22-year-female patient. On radiographic examination, a radiolucent lesion in the region of tooth 36 to 44 with tooth displacement and alveolar cortical resorption was observed. Histopathological study revealed a malignant neoplasm of the odontogenic epithelium, composed of PAS-positive clear cells and immunoreactivity for CK5, CK7, CK19, p63. The Ki-67 index was low (<10 %). Fluorescent in situ hybridization revealed EWSR1 gene rearrangement. The diagnosis of CCOC was established and the patient was referred for surgical treatment.

A novel SMARCA2-CREM fusion expending the molecular spectrum of salivary gland hyalinazing clear cell carcinoma beyond the FET genes

Hyalinizing clear cell carcinoma (HCCC) is a rare salivary gland carcinoma with a generally indolent behavior, characterized by recurrent chromosomal translocation involving EWSR1 (22q12.2) leading to two fusion genes EWSR1::ATF1 or EWSR1::CREM. We report one case of HCCC with a novel SMARCA2::CREM fusion, identified by targeted RNA next generation sequencing by LD-RT-PCR, which has until now never been described in salivary glands. The exon 4 of SMARCA2 is fused to exon 5 of CREM. This fusion has been described previously in only one tumor, a central nervous system tumor (intracranial mesenchymal tumor) but not in other FET::CREB fused tumors. This fusion was confirmed by CREM break-apart FISH and reverse transcriptase polymerase chain reaction (RT-PCR). The tumor cells showed retained expression of INI1, SMARCA2, and SMARCA4 by immunohistochemistry. We compare its clinical, histopathological, immunophenotypic, genetic features with those previously described in HCCC, FET::CREB fusion-positive. Our results added data suggesting that different histomolecular tumor subtypes seem to be included within the terminology "HCCC, FET::CREB fusion-positive," and that further series of cases are needed to better characterize them.

Top 10 Clear Cell Head and Neck Lesions to Contemplate

BACKGROUND

Optically clear cytoplasm may occur in neoplastic and non-neoplastic conditions, either as a characteristic feature of a disease entity or as a morphologic rarity, potentially creating diagnostic dilemmas in various organ systems. In the head and neck, clear cell change can occur in lesions of salivary, odontogenic, thyroid, parathyroid, or sinonasal/skull base origin, as well as in metastases to these regions.

METHODS

This review elaborates the top ten clear cell lesions in the head and neck, emphasizing their distinguishing histologic, immunohistochemical, and molecular attributes, and presents a rational approach to arriving at an accurate classification.

RESULTS

Cytoplasmic pallor or clearing may be caused by accumulations of glycogen, lipid, mucin, mucopolysaccharides, water, foreign material, hydropic organelles, or immature zymogen granules. Overlapping morphologic features may present a diagnostic challenge to the surgical pathologist. Similarity in immunohistochemical profiles, often due to common cell type, as well as rare non-neoplastic mimics, furthers the diagnostic conundrum.

CONCLUSIONS

The top ten lesions reviewed in this article are as follows: (1) clear cell carcinoma (salivary and odontogenic), (2) mucoepidermoid carcinoma, (3) myoepithelial and epithelial-myoepithelial carcinoma, (4) oncocytic salivary gland lesions, (5) squamous cell carcinoma, (6) parathyroid water clear cell adenoma, (7) metastatic renal cell carcinoma (especially in comparison to clear cell thyroid neoplasms), (8) sinonasal renal cell-like adenocarcinoma, (9) chordoma, and (10) rhinoscleroma.

Maxillary clear cell odontogenic carcinoma with EWSR1-ATF1 fusion gene mimicking sclerosing odontogenic carcinoma: A case report and literature review

Both clear cell odontogenic carcinoma (CCOC) and sclerosing odontogenic carcinoma (SOC) are rare odontogenic malignancies. Here, we report a case of maxillary CCOC whose clinical and histologic features resembled those of SOC. Radiologically, the tumor presented as an ill-defined, expansile radiolucency with local bone destruction. Histologically, the tumor was comprised of thin cords or strands of odontogenic epithelium permeating through a sclerosed fibrous stroma with occasional clear cell foci. It damaged the cortical plates and invaded the adjacent soft tissue. Immunohistochemical expression of Pancytokeratin, Cytokeratin 19, p63, Cytokeratin 5/6, and Cytokeratin 14, as well as focal expression of Cytokeratin 7, demonstrated the epithelial nature of the tumor. Alcian Blue Periodic acid Schiff staining revealed a lack of intracellular mucin. Fluorescence in situ hybridization analysis revealed Ewing sarcoma RNA binding protein 1 and activating transcription factor 1 gene translocation, further confirming the diagnosis of CCOC. Lastly, we contextualized the genetic analysis of our case to that of CCOC in the literature.

Sclerosing Odontogenic Carcinoma: Report of a Case and Review of the Literature

BACKGROUND

Sclerosing odontogenic carcinoma is an exceedingly rare gnathic malignancy first described by Koutlas et al. in 2008, and was only recently designated as a distinct pathologic entity by World Health Organization in the 2017 Classification of Head and Neck Tumors. To date, fewer than fifteen cases of this neoplasm have been reported in the English language literature. This tumor is characterized by thin cords, strands, and small nests of epithelium in a densely sclerotic stroma. In some tumor foci, the density of the stroma may be sufficient to compress the epithelial component beyond detection in the absence of immunohistochemistry, thus rendering this entity a particularly challenging diagnosis in small sample sizes.

METHODS

A 55-year-old male presented with an asymptomatic lesion of posterior left maxilla. Cone beam computed tomography (CBCT) demonstrated a large, well-defined bony lesion with scalloped border, spanning from canine to first molar. External root resorption of the adjacent teeth was also noted. Microscopic examination of the biopsy specimen revealed an odontogenic tumor with features consistent with sclerosing odontogenic carcinoma. Immunohistochemical staining was performed to confirm the diagnosis.

RESULTS

The tumor was positive for CK5/6, CK19, E-cadherin, p63 and negative for CK20 and CK7.

CONCLUSION

Sclerosing odontogenic carcinoma is a rare, low-grade malignancy of odontogenic origin, which represents a diagnosis of exclusion in many cases. An immunohistochemical profile demonstrating positivity for markers including CK5/6, CK19, p63, and E-cadherin, in addition to a set of pertinent negative findings, can aid in the diagnosis of this tumor. This entity appears to lack metastatic potential despite its locally destructive behavior and a common histologic finding of perineural invasion.

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.

Malignant odontogenic tumors. A report of a series of 30 cases and review of the literature

Malignant odontogenic tumors are rare entities and can arise de novo or from malignant transformation of pre-existing lesions. The aim of the present study was to report 30 cases of malignant odontogenic tumors diagnosed at a single diagnostic center over a 38-year period.

MATERIALS AND METHODS

All cases of malignant odontogenic tumors diagnosed between 1980 and 2018 were retrieved from the files of the School of Dentistry, University of Buenos Aires; their frequency and clinical, radiographic, and histopathological features were analyzed. The obtained data were compared with the information reported in the literature.

RESULTS

Malignant odontogenic tumors accounted for 2 % of odontogenic tumors and 0.05 % of all oral-maxillofacial diseases. Mean age was 43 years (8 to 87 years). No differences in sex distribution were observed. The most frequent location was the mandible, mostly the posterior mandibular body and the ramus. Odontogenic carcinomas were the most frequent tumors, and primary intraosseous carcinomas were the most common in this group.

CONCLUSIONS

This is the largest case series of malignant odontogenic tumors diagnosed at a single center reported in the literature to date. Diagnosis of these tumors is challenging based on their rarity and complexity and relies on careful analysis of the histopathological, clinical, and radiographic features.

Comprehensive genomic profiling of EWSR1/FUS::CREB translocation-associated tumors uncovers prognostically significant recurrent genetic alterations and methylation-transcriptional correlates

To elucidate the mechanisms underlying the divergent clinicopathologic spectrum of EWSR1/FUS::CREB translocation-associated tumors, we performed a comprehensive genomic analysis of fusion transcript variants, recurrent genetic alterations (mutations, copy number alterations), gene expression, and methylation profiles across a large cohort of tumor types. The distribution of the EWSR1/FUS fusion partners-ATF1, CREB1, and CREM-and exon involvement was significantly different across different tumor types. Our targeted sequencing showed that secondary genetic events are associated with tumor type rather than fusion type. Of the 39 cases that underwent targeted NGS testing, 18 (46%) had secondary OncoKB mutations or copy number alterations (29 secondary genetic events in total), of which 15 (52%) were recurrent. Secondary recurrent, but mutually exclusive, TERT promoter and CDKN2A mutations were identified only in clear cell sarcoma (CCS) and associated with worse overall survival. CDKN2A/B homozygous deletions were recurrent in angiomatoid fibrous histiocytoma (AFH) and restricted to metastatic cases. mRNA upregulation of MITF, CDH19, PARVB, and PFKP was found in CCS, compared to AFH, and correlated with a hypomethylated profile. In contrast, S100A4 and XAF1 were differentially upregulated and hypomethylated in AFH but not CCS. Unsupervised clustering of methylation profiles revealed that CREB family translocation-associated tumors form neighboring but tight, distinct clusters. A sarcoma methylation classifier was able to accurately match 100% of CCS cases to the correct methylation class; however, it was suboptimal when applied to other histologies. In conclusion, our comprehensive genomic profiling of EWSR1/FUS::CREB translocation-associated tumors uncovered mostly histotype, rather than fusion-type associated correlations in transcript variants, prognostically significant secondary genetic alterations, and gene expression and methylation patterns.

Detection of EWSR1 fusions in CCOC by targeted RNA-seq

OBJECTIVE

To describe the application of a targeted RNA sequencing assay to detect fusion transcripts in formalin-fixed paraffin-embedded (FFPE), non-decalcified samples of clear cell odontogenic carcinoma (CCOC) and related tumors, and to add to knowledge of the genetic drivers of CCOC.

STUDY DESIGN

Five FFPE tissues, including intraosseous CCOC (n = 3), clear cell carcinoma of the salivary gland (CCC, n = 1), and Ewing sarcoma (ES, n = 1), were analyzed by targeted RNA-seq to detect fusions.

RESULTS

The 3 intraosseous CCOC samples harbored EWSR1 translocations: EWSR1-ATF1 (n = 2) and EWSR1-CREM (n = 1); the CCC sample contained an EWSR1-ATF1 fusion; and the ES sample contained an EWSR1-FLI1 fusion detected by RNA-seq.

CONCLUSIONS

These results demonstrate that targeted RNA-seq is a valuable tool to detect fusions in FFPE samples of rare tumors such as CCOC and CCC. The results also confirm the observations that CCOC is driven by fusions between EWSR1 and CREB family transcription factors, including ATF1 and CREM. To our knowledge, this is the second report of CCOC with an EWSR1-CREM translocation.

Clear Cell Neoplasms of Salivary Glands: A Diagnostic Challenge

This review focuses on the heterogenous group of clear cell neoplasms of salivary glands and attempts to identify major differential diagnostic features. Within the head and neck region, clear cells are found most commonly in salivary gland tumors, but may also be seen in tumors of squamous or odontogenic epithelial origin, primary or metastatic carcinomas, benign or malignant melanocytic lesions, or benign or malignant mesenchymal tumors. Clear cells occur fairly commonly among a wide variety of salivary gland neoplasms, but mostly they constitute only a minor component of the tumor cell population. Clear cells represent a major diagnostic feature in two salivary gland neoplasms, epithelial-myoepithelial carcinoma and hyalinizing clear cell carcinoma. In addition, salivary gland neoplasms composed predominantly of clear cells could also include clear cell variants of other salivary neoplasms, such as mucoepidermoid carcinoma and myoepithelial carcinoma, but their tumor type-specific histologic features may only be available in limited nonclear cell areas of the tumor. Diagnosing predominantly clear cell salivary gland tumors is difficult because the immunoprofiles and morphologic features may overlap and the same tumor entity may also have a wide range of other histologic presentations. Many salivary gland tumors are characterized by tumor type-specific genomic alterations, particularly gene fusions of the ETV6 gene in secretory carcinoma, the MYB and MYBL1 genes in adenoid cystic carcinoma, the MAML2 gene in mucoepidermoid carcinoma, the EWSR1 gene in hyalinizing clear cell carcinoma, and others. Thus, along with conventional histopathologic examination and immunoprofiling, molecular and genetic tests may be important in the diagnosis of salivary gland clear cell tumors by demonstrating genetic alterations specific to them.

Ameloblastic Carcinoma of the Maxilla: A Rare Case Report and Review of Literature from 1948 to 2021

Ameloblastic carcinoma is a rare malignant neoplasm arising from the odontogenic epithelium. Ameloblastic carcinoma commonly occurs de novo affecting the posterior segments of the mandible. Presently, only less than 100 cases have been reported arising from the maxilla. We report a unique case of maxillary ameloblastic carcinoma in a 68-year-old male with a 5.6 cm positron emission tomography (PET) avid left maxillary sinus mass. The patient underwent a left maxillectomy which revealed hyperchromatic and pleomorphic tumor cells arranged in a nested and trabecular architecture. The tumor cells showed distinct peripheral palisading with reverse polarization. Areas of bone destruction, necrosis, lymphovascular and perineural invasions, as well as atypical mitoses, were identified. Immunohistochemically, the tumor cells were positive for keratin cocktail (AE1/AE3 and CAM 5.2), keratin 19, p40, and weakly positive for MDM2, while negative for calretinin. Molecular analysis revealed wild-type BRAF; however, alterations in CDKN2A/B, MTAP, RB1, SMARCA4, STK11, FGF12, SETD2, and TP53 were present. This histopathologic and molecular profile supported the diagnosis of ameloblastic carcinoma. There has been no evidence of disease recurrence or metastasis eleven months after the initial diagnosis.

The evolving role of molecular pathology in the diagnosis of salivary gland tumours with potential pitfalls

Salivary gland tumors are diagnostically challenging owing to the morphological diversity within any tumor type and overlapping histomorphology and immunohistochemistry amongst different tumours. In past two decades, rapid progress has been made in the field of understanding the pathogenesis of these tumours with the discovery of many tumour specific translocations and rearrangements. This includes CRTC1-MAML2 and CRTC-MAML2 in mucoepidermoid carcinoma, MYBNFIB and MYBL1-NFIB fusions in adenoid cystic carcinoma, PLAG1 and HMGA2 in pleomorphic adenoma, ETV6-NTRK3 in secretory carcinoma, NR4A3 rearrangements in acinic cell carcinoma, PRKD1 mutations in polymorphous adenocarcinoma and EWSR1-ATF1 in clear cell carcinoma. This review is a lens for progress made till date in the molecular pathology of salivary gland tumours with a special focus on their role as diagnostic tools and implications on clinical management of the patient as prognostic and predictive markers.

Clear Cell Odontogenic Carcinoma: A Series of Three Cases

Background: Clear cell odontogenic carcinoma (CCOC) is a rare malignant odontogenic epithelial neoplasm of the jaws. It is composed of irregular nests of clear to faintly eosinophilic cells resembling clear cell rests of primitive dental lamina and an intermixed hyalinized fibrous stroma. Most cases occur in the 5th and 6th decades of life, with a female predominance. The mandible is affected more than the maxilla. Clinical features vary from asymptomatic to non-specific pain, ill-defined radiolucency, root resorption, and sometimes soft tissue extension. Histology varies from bland to high grade. CCOC demonstrated a significant tendency to recur. Metastasis typically involves regional lymph nodes, which haves been reported in 20–25% of cases. Pulmonary metastasis rarely occurs. Differential diagnoses are broad and include odontogenic, salivary, melanocytic, and metastatic neoplasia. CCOCs are positive for cytokeratins, mainly AE1/AE3 and CK19. Most cases show EWSR1 rearrangement and rarely, the BRAFV600E mutation. Design: Patient charts were reviewed at our institution. A total of three cases were found in electronic medical records, which were diagnosed as clear cell odontogenic carcinoma over a period of six years (2014–2019). Patient charts were reviewed for medical history and radiology data. The pathology slides were reviewed by one or more faculty members. Results: We present three cases of CCOC, ranging in age from 40 to 69 years (two women and one man). Two cases involved the maxilla and one involved the mandible. Two presented with painful swelling and one with mass recurrence. Radiography results show that two had poorly defined radiolucent lesions, and one was heterogeneous with a small nodule projecting into the maxillary sinus. Histological examination revealed an epithelial neoplasm composed of irregular sheets, cords, and nests of polygonal cells with central hyperchromatic, mildly pleomorphic nuclei surrounded by clear to pale eosinophilic cytoplasm, with occasional mitotic figures. The tumor had infiltrated the bone and soft tissues. Two cases were immunopositive for CK5/6 and one case was positive for p63 and CK19. Interestingly, the eosinophilic dentinoid matrix interspersed among tumor cells in one case was consistent with its odontogenic origin. Histochemical staining showed PAS-positive and diastase-labile intracytoplasmic material consistent with glycogen. Conclusion: Our study highlights the potential diagnostic significance of dentinoid (although reportedly seen in only 7% of cases), along with CK5/6 immunopositivity, in supporting the histologic diagnosis of CCOC among a variety of neoplasia in its differential diagnosis.

Clinicopathological and molecular study of 10 salivary gland clear cell carcinomas, with emphasis on rare cases with high grade transformation and occurring in uncommon sites

Background

As a rare salivary gland malignancy, clear cell carcinoma (CCC) is easily misdiagnosed. This study identified the features that allow better recognition of the clinicopathological and molecular characteristics and the prognosis of CCC, focusing on high-grade transformation (HGT) in this tumor and cases arising in uncommon sites.

Methods

Clinicopathological and follow-up data for 10 CCC samples were retrieved. Immunohistochemical (IHC) staining was performed, and fluorescence in situ hybridization (FISH) was used to detect EWSR1 gene rearrangements, EWSR1–ATF1 gene fusions, and MAML2 gene rearrangements.

Results

Histologically, typical CCCs comprised bland polygonal or round cells with clear cytoplasm. In contrast with typical CCCs, HGT tumor cells exhibited nuclear pleomorphism, high nuclear-to-cytoplasmic ratios, high mitotic activity, and necrosis. Rare morphologic features such as pseudopapillae, gland-like spaces, and entrapped ducts were also observed. Occasionally, tumors involving the oral cavity might arise from the overlying epithelium of the mucosal surface. Immunohistochemically, all the cases expressed p63, p40, and CK5/6, while myoepithelial-related markers were uniformly negative in all cases. HGT exhibited a wild type p53 expression pattern. FISH demonstrated EWSR1 rearrangement (10/10) and EWSR1–ATF1 fusion (4/5); however, MAML2 remained intact (0/3).

Conclusions

CCCs with HGT or occurring in uncommon sites are extremely rare. Combining morphology based IHC and molecular detection provided reliable evidence that the HGT component represented a transformation of CCC rather than the coexistence of another tumor and helped differentiating CCCs in uncommon sites from their mimics, avoiding potential misdiagnosis and inappropriate therapy. The overall prognosis for CCCs is good, except for the HGT cases, which needed continued treatment.

Fusion-Positive Salivary Gland Carcinomas

Salivary gland tumors are a rare, heterogeneous group of neoplasms that pose significant diagnostic challenges for the histopathologist. Histopathological diagnosis relies primarily on morphological assessment, with ancillary special stains and immunohistochemistry. In recent years, new defining genomic alterations have been characterized in these tumors. In particular, they include gene fusions which have shown to be tightly tumor-type specific, and thus valuable for use in diagnostically challenging cases. These discoveries also help in refining tumor classification. Furthermore, such genetic alterations may have prognostic as well as potentially therapeutic implications in the era of personalized medicine. This review aims at providing a summary of the most recent updates in this field.

Clear cell carcinoma: a comprehensive literature review of 254 cases

This comprehensive literature review represents a summary of all cases of clear cell carcinoma (CCC) of the salivary glands that are documented in the literature. PubMed was used to collect available reports of CCC; 97 reports detailing 254 cases, published between 1983 and 2020, were retrieved. Clinically the tumor manifests most commonly as a painless mass or swelling on the palate, and the duration of symptoms prior to seeking care ranges from 1 week to 6 years. Local tumor recurrence was present in 18.8% of the cases. By histopathology, CCC shows a mixture of growth patterns including solid (25.1%), nested (78.6%), sheet-like (23.5%), cords (46.1%), and trabeculae (42.4%). Immunohistochemical studies are positive for one or more cytokeratins (99.1%), PAS (95.1%), EMA (77.8%), and p63 (96.3%), but negative for S-100 (96.3%), PASD (91.1%), SMA (91.0%), and calponin (95.1%). Molecular features were reported in 113 cases; 96.0% were positive for an EWSR1 rearrangement by EWSR1 break apart FISH testing and 14.8% were positive for the rearrangement EWSR1-ATF1 tested by qPCR or targeted RNA sequencing. Clinical patterns and genetic studies imply that this tumor is the extraosseous counterpart of clear cell odontogenic carcinoma, an intraosseous odontogenic tumor of the jaws.

Clear Cell Odontogenic Carcinoma a Systematic Review

Clear cell Odontogenic Carcinoma (CCOC) is an uncommon malignant odontogenic tumor (MOT). It is the fifth most common MOT. A systematic review is presented of reported cases, case series and retrospective studies of CCOC, to determine trends in presentation, diagnostic features, treatment, and patient outcome. Searches of detailed databases were carried out to identify papers reporting CCOC. The variables were demographics, patient symptoms, tumor location, histopathological findings, immunohistochemical studies, treatment, follow-up, and recurrence. 117 cases were identified; CCOC was most frequently seen in mature females 65% (n = 76). The total average age was 55.4 with a range from 17 to 89 years, for females 56.4 and males 53.6 years. The mean size was 3.41 cm. The most common location was in the mandibular body 36.2% (n = 42), followed by the anterior mandible 23.3% (n = 27). The most common clinical presentation was a swelling 80.4% (n = 74), and the main symptom was pain 41.3% (n = 31), followed by painless lesion 24% (n = 18). The most common Immunohistochemistry positive expression was CK19, EMA, and CEA, and for special staining periodic acid Shiff (PAS); 97% of cases were treated surgically. The average follow-up was 30.3 months, and recurrence was reported in 52.4% of the cases. Conclusion: CCOC shows a strong predilection for the body and anterior mandible, and females are more frequently affected. CCOCs can be painful and the principle clinical sign is swelling, CCOCs can metastasize, and the prognosis is fair.

Malignant lesion of clear cells: A diagnostic challenge of an unusual presentation mimicking a benign lesion

In the oral cavity, a broad spectrum of differential diagnostics includes lesions composed of clear cells. Under this umbrella, Clear Cell Odontogenic Carcinoma (CCOC) and Hyalinizing Clear Cell Carcinoma (HCCC) are rare malignancies that arise from different histological origins. However, the histology is similar; therefore, differentiation of CCOC and HCCC lesions is difficult and, in some cases, impossible to distinguish morphologically and immunohistochemically. Herein, we report an unusual presentation of a well-defined nodular lesion affecting the maxillary gingiva in a 19-year-old female, which presented clinically as a benign or reaction etiology lesion. Microscopic evaluation showed a tumor composed of cell sheets with clear cytoplasm, separated by septa of fibrous tissue and invading the connective tissue. Tumor cells were positive for p63 and AE1/AE3 and negative for PAX8, smooth muscle actin (AML) and estrogen receptor. The diagnosis was carcinoma with a clear cell pattern, and it was not possible to distinguish between HCCC and CCOC. In this study, clinicopathologic, histologic, and immunohistochemistry features of CCOC and HCCC were discussed due to the challenging histological diagnosis. Radical surgical treatment and rehabilitation of the patient through graft and dental implants were performed. The patient is under follow-up with no signs of recurrence.

Retrospective analysis of primary intraosseous malignancies in mandible and maxilla in a population of Taiwanese patients

BACKGROUND/PURPOSE

Due to the rarity and diversity of primary intraosseous malignancies in jawbones, we aimed to evaluate the clinicopathological features and discuss the findings of our collected cases with the literatures.

METHODS

Twenty-nine patients (2000-2020) diagnosed with primary central malignancies of jawbones were selected from the database of Oral Pathology Department in our institution. Clinical features, radiographic appearance, and histopathological diagnosis of the 29 cases were analyzed.

RESULTS

Twenty-nine patients aged between 19 and 84 years (average, 57.4 years) with a male to female ratio of 1.2:1 were included. The most frequent site was the mandibular body and ramus, followed by the posterior maxilla and mandibular symphysis. The most common diagnosis was osteogenic sarcoma (n = 13), followed by odontogenic carcinoma (n = 7), hematologic malignancies (n = 5), salivary gland malignancies (n = 2), and neurogenic sarcomas (n = 2). The most frequent symptoms were swelling, pain, paresthesia of lower lip, and mobile tooth. Radiographically, they usually presented as ill-defined osteolytic to osteoblastic lesions depending on the amount of ossification. Wide excision comprising partial maxillectomy and segmental mandibulectomy were the most common therapeutic methods.

CONCLUSION

Despite the rarity of primary central malignancies in jawbones, the clinical features may mimic infectious process or benign lesions. Detailed history-taking, clinical and imaging examination and awareness of the patient's signs and symptoms combining with the histopathological inspection are important for early diagnosis and improved prognosis. The current data contributes a useful basis for clinical investigation regarding intraosseous malignancies occurring in the jawbones.

Clear Cell Carcinoma in the Oral Cavity with Three Novel Types of EWSR1-ATF1 Translocation: A Case Report

Clear cell carcinoma (CCC) is a rare epithelial malignant tumor of the salivary glands. It is characterized by tumor cells with clear cytoplasm, hyalinized stroma, and most importantly the fusion genes EWSR1-ATF1, EWSR1-CREM, and EWSR1-PLAG1. Break-apart FISH has been performed for multiple CCC cases, but direct sequencing analysis has been performed in relatively few. Herein, we report an interesting case of CCC harboring three EWSR1-ATF1 translocations: EWSR1 exon 8-ATF1 exon 4, EWSR1 exon 7-ATF1 exon 4, and EWSR1 exon 7-ATF1 exon 5. This case indicates the possibility of independent EWSR1-ATF1 gene translocations, and could provide insight into CCC tumorgenesis.

Updates in the molecular pathology of non-small cell lung cancer

An understanding of the molecular pathology of non-small cell lung cancer (NSCLC) is important for pathologists as molecular characterization is now required for treatment decisions in advanced stage disease. While assessment for EGFR mutations, ALK and ROS1 fusions, and in some countries BRAF mutations, is now standard practice, other oncogenic mutations are also emerging that may impact routine clinical practice including alterations involving KRAS, NTRK, RET, MET and HER2. In addition, molecular pathology alterations of NSCLC are associated with responses to immune checkpoint therapy and are being increasingly investigated. Finally, specific molecular pathological alterations define some rarer subtypes of NSCLC such as salivary gland tumours, NUT carcinoma and SMARCA4-deficient undifferentiated tumour, and an understanding of the molecular pathology is important for their accurate diagnosis. In this review, the molecular pathology of NSCLC is discussed with a focus on clinically relevant molecular alterations.

Clear Cell Odontogenic Carcinoma of the Mandible Harboring EWSR1 Rearrangement: Report of a Massive Jaw Tumor and Review of Diagnostic Considerations

Clear cell odontogenic carcinoma (CCOC) is a low-grade malignant neoplasm that affects the jaws. We report an 18 cm massive case of mandibular CCOC in a 43-year-old female. The tumor was composed of nests and cords of round to polygonal monomorphic clear cells separated by prominent stromal hyalinization. Immunohistochemically, the tumor cells showed focal cytokeratin 5/6 positivity and intracytoplasmic PAS-positive granules and were negative for S100 and after diastase treatment (PAS-D). Molecularly, this case was positive for EWSR1 rearrangement by FISH. The following should be included in the histopathological differential diagnosis: hyalinizing clear cell carcinoma of the salivary gland, clear cell variant of central mucoepidermoid carcinoma, clear cell variant of calcifying epithelial odontogenic tumor, and metastatic renal cell carcinoma. CCOC is a rare entity, with only 79 cases reported in the mandible. This case highlights the propensity for CCOC to exhibit invasiveness, destructive nature, and facial disfigurement if left untreated.

Clinico-pathological study of malignant odontogenic tumours from a national referral centre

BACKGROUND

Malignant odontogenic tumours are extremely rare tumours occurring within the jaws. Our study was performed to determine the demographic and clinico-pathological features of malignant odontogenic tumours amongst a multi-ethnic Asian population.

METHODS

This was a retrospective cross-sectional study of malignant odontogenic tumours diagnosed at the Institute for Medical Research, Malaysia, from 2009 to 2019. All cases were independently reviewed and reclassified following the criteria set out in the latest edition of the World Health Organization 2017 reference text. Demographic and clinico-pathological data were recorded for each case.

RESULTS

Twenty-four cases of malignant odontogenic tumours were identified. The patients' age ranged from 16 to 79 years with the mean age at diagnosis being 50.8 years (SD = 16.18). There was a male predominance (66.7%) in this cohort of patients. The ethnic distribution appeared to reflect the Malaysian population with most cases seen amongst the Malay ethnic group (66.7%). Ameloblastic carcinoma was the most frequently diagnosed malignant odontogenic tumour (45.8%) and was also predominantly seen in males (90.9%). All patients with clear cell odontogenic carcinoma were females. There was no obvious sex predilection in primary odontogenic carcinoma not otherwise specified (NOS). The mandible (79.2%) was more frequently involved compared to the maxilla.

CONCLUSIONS

Diagnosis and management of malignant odontogenic tumours are challenging due to the rarity of these tumours. Our study has elucidated the clinico-pathological features of malignant odontogenic tumours seen in a multi-ethnic Asian population.

Molecular Pathology of Salivary Gland Neoplasms: Diagnostic, Prognostic, and Predictive Perspective

Salivary gland neoplasms are an uncommon and widely heterogeneous group of tumors. In recent years, there has been considerable progress in efforts to reveal the molecular landscape of these tumors, although it is still limited and appears to be only the tip of the iceberg. Genomic aberrations, especially specific chromosomal rearrangements including CRTC1-MAML2 and CRTC3-MAML2 in mucoepidermoid carcinoma, MYB-NFIB and MYBL1-NFIB fusions in adenoid cystic carcinoma, PLAG1 and HMGA2 alterations in pleomorphic adenoma and carcinoma ex pleomorphic adenoma, ETV6-NTRK3 and ETV6-RET in secretory carcinoma, EWSR1-ATF1 and EWSR1-CREM in clear cell carcinoma, provide new insights into the molecular pathogenesis of various salivary gland neoplasms and help to better classify them. These genetic aberrations primarily serve as diagnostic tools in salivary gland tumor diagnosis; however, some also have promise as prognostic or predictive biomarkers. This review summarizes the latest developments in molecular pathology of salivary gland tumors with a focus on distinctive molecular characteristics.

Clear Cell Odontogenic Carcinoma: First Report of Novel EWSR1-CREM Fusion Gene in Case of Long-Term Misdiagnosis

Clear Cell odontogenic Carcinomas (CCOC) are rare, aggressive malignant odontogenic tumours which are often misdiagnosed as benign odontogenic tumours due to the non-specific histologic appearance, and benign early clinical presentation. However, due to their propensity to metastasize, the best outcomes are experienced with they are diagnosed early and treated aggressively. In this paper, we present a case of a CCOC misdiagnosed as a clear cell calcifying epithelial odontogenic tumour which was only found to be a CCOC after cervical node metastasis. The original diagnosis was questioned and confirmed to be a CCOC by identification of the chromosomal translocation EWSR1 on fluorescence in situ hybridization. This has recently been described in CCOC and a wide variety of other mesenchymal and epithelial neoplasms. Previous reports have demonstrated EWSR1-ATF1 and EWSR1-CREB1 fusions in CCOC. Next generation sequencing of this case demonstrated the EWSR1-CREM fusion gene which has not been previously reported for CCOC. CREM fusion proteins have only recently been found in several tumour types including the closely associated hyalinizing clear cell carcinoma of salivary glands. This is discussed in this paper, and the role of the discovery of the CREM fusion protein in CCOC adds to your understating of the role of CREM in oncogenesis, and the possible link between CCOCs and hyalinizing clear cell carcinomas.

A contemporary update on hyalinizing clear cell carcinoma: compilation of all in-house cases at our institution and a literature review spanning 2015-2020

Tumors of the head and neck with clear cell features prompt a broad differential diagnosis. A relatively uncommon, but increasingly recognized, entity is hyalinizing clear cell carcinoma (HCCC). This neoplasm, first described in 1994, consists of clear cells arranged in nests or trabecule with a hyalinized stroma. These are low-grade neoplasms that only infrequently metastasize and rarely recur. They also often harbor a unique EWSR-ATF1 gene rearrangement. As the prognosis is excellent compared with other clear cell neoplasms, the correct diagnosis is key. Here we present all of the cases of HCCC in the past decade from our institution alongside a comprehensive literature review spanning 2015-2020 to further characterize this unusual malignancy.

EWSR1-SMAD3 fibroblastic tumour of bone: expanding the clinical spectrum

EWSR1-SMAD3 fibroblastic tumour is a recently described soft tissue lesion. To date, eight cases have been reported, all sited in superficial soft tissue, typically occurring in the hands and feet with a tendency for local recurrence if incompletely excised. No metastatic spread has been reported, and hence, these tumours are currently considered benign. Herein, we present the radiological and histological features of the first reported occurrence of this entity in bone: a 44-year-old man with a tumour in the right tibia, treated with en bloc resection and showing no signs of relapse at 7 years. This tumour should be added to the differential diagnosis of bone lesions which harbour EWSR1 gene rearrangement.

Molecular Profiling of Clear Cell Myoepithelial Carcinoma of Salivary Glands With EWSR1 Rearrangement Identifies Frequent PLAG1 Gene Fusions But No EWSR1 Fusion Transcripts

Myoepithelial carcinoma of salivary glands is an underrecognized and challenging entity with a broad morphologic spectrum, including an EWSR1-rearranged clear cell variant. Myoepithelial carcinoma is generally aggressive with largely unknown genetic features. A retrospective review of Salivary Gland Tumor Registry in Pilsen searching for the key words "clear cell myoepithelial carcinoma," "hyalinizing clear cell," and "clear cell malignant myoepithelioma" yielded 94 clear cell myoepithelial carcinomas (CCMCs) for molecular analysis of EWSR1 rearrangement using fluorescence in situ hybridization (FISH). Tumors positive for EWSR1 gene rearrangement were tested by next-generation sequencing (NGS) using fusion-detecting panels. NGS results were confirmed by reverse-transcription polymerase chain reaction or by FISH. Twenty-six tumors originally diagnosed as CCMC (26/94, 27.6%) revealed split signals for EWSR1 by FISH. Six of these tumors (6/26, 23%) displayed amplification of the EWSR1 locus. Fifteen cases were analyzable by NGS, whereas 9 were not, and tissue was not available in 2 cases. None of the CCMCs with EWSR1 rearrangements detected by FISH had an EWSR1 fusion transcript. Fusion transcripts were detected in 6 cases (6/15, 40%), including LIFR-PLAG1 and CTNNB1-PLAG1, in 2 cases each, and CHCHD7-PLAG1 and EWSR1-ATF1 fusions were identified in 1 case each. Seven cases, including those with PLAG1 fusion, were positive for PLAG1 rearrangement by FISH, with notable exception of CHCHD7-PLAG1, which is an inversion not detectable by FISH. One single case with EWSR1-ATF1 fusion in NGS showed ATF1 gene rearrangement by FISH and was reclassified as clear cell carcinoma (CCC). In addition, another 4 cases revealed ATF1 rearrangement by FISH and were reclassified as CCC as well. Moreover, 12/68 (17%) CCMCs with intact EWSR1 gene were selected randomly and analyzed by NGS. PLAG1 fusions were found in 5 cases (5/12, 41.6%) with LIFR (2 cases), FGFR1 (2 cases), and CTNNB1 (1 case) as partner genes. Overall, PLAG1 gene rearrangements were detected in 10/38 (26%) tested cases. None of the tumors had SMARCB1 loss by immunohistochemistry as a possible explanation for the EWSR1 abnormalities in FISH. Novel findings in our NGS study suggest that EWSR1-FISH positive CCMC is a gene fusion-driven disease with frequent oncogenic PLAG1 fusions, including LIFR-PLAG1 and CTNNB1-PLAG1 in most cases. Productive EWSR1 fusions are found only in a minority of EWSR1-ATF1-rearranged cases, which were in part reclassifiable as CCCs. Detectable EWSR1-FISH abnormality in CCMCs without gene fusion perhaps represents a passenger mutation with minor or no oncologic effect.

Survey of Paediatric Oncologists and Pathologists regarding Their Views and Experiences with Variant Translocations in Ewing and Ewing-Like Sarcoma: A Report of the Children's Oncology Group

Advances in molecular diagnostics have identified subsets of Ewing and Ewing-like sarcomas driven by variant translocations with unique biology. It is likely that patients with these tumours will have different clinical features and therapeutic outcomes. Nevertheless, the management of these patients both locally and within cooperative group trials depends on the local pathological diagnosis. It is not known what molecular diagnostic approaches are employed by local pathologists or if the exact translocation is commonly determined. In addition, it is not known what therapeutic approaches are employed for these patients or what cooperative trials are deemed appropriate for these patients by expert consensus. To answer these questions, we performed an international survey of oncologists and pathologists to better understand the diagnostic approaches used to identify variant translocations and the influence the findings have on therapy and clinical trial eligibility. An online survey was distributed to oncologists and pathologists primarily in North America. A total of 141 surveys were completed, representing a 28% response rate. The majority of respondents considered EWSR1-ETS gene family translocations (range 61–96%) to be Ewing sarcoma and would include them on the primary arm of a Ewing sarcoma clinical trial. There was a lack of consensus on how to classify and stratify BCOR-CCNB3, CIC-DUX4, and EWSR1+ with non-ETS partner fusions. Most respondents were either unsure how their institution tested, or their institution did not perform the test. In cases with atypical Ewing morphology, most respondents favoured additional fusion transcript testing. There is a lack of consensus regarding the classification and stratification of rare molecular subtypes in Ewing sarcoma. It is not clear how these alternative translocations have impacted outcomes for past clinical studies. This suggests a need for molecular confirmation of diagnoses and centralized or minimum standardization of testing for future trial enrolment.

Whole Exome Sequencing of SMO, BRAF, PTCH1 and GNAS in Odontogenic Diseases

BACKGROUND/AIM

Odontogenic diseases are diagnosed based on clinical course, imaging, and histopathology. However, a definitive diagnosis is not always possible.

PATIENTS AND METHODS

We analyzed whole exons of SMO, BRAF, PTCH1 and GNAS using next-generation sequencing (NGS) in 18 patients.

RESULTS

Of the 6 patients with ameloblastoma, 2 patients had the same missense mutation in BRAF, and 1 patient with peripheral ameloblastoma had a missense mutation in PTCH1. Of the 7 patients with odontogenic keratocyst, 4 patients had a missense mutation in PTCH1, 2 patients had missense mutations in BRAF, and 1 patient had a missense mutation in SMO. The patient with odontoma had missense mutations in SMO, BRAF and PTCH1. One patient with cement-osseous dysplasia had missense mutations in SMO and PTCH1. The patient with adenomatoid odontogenic tumor had missense mutations in SMO.

CONCLUSION

Whole exome sequencing of the above genes by NGS would be useful for the differential diagnosis of odontogenic diseases.

World Health Organization Classification of Odontogenic Tumors and Imaging Approach of Jaw Lesions

Tumors of the jaws represent a heterogeneous group of lesions that are classified histologically in the World Health Organization Classification of Odontogenic Tumors (2017). This article provides an update of the current nomenclature. The main role of imaging is to describe the precise location and extent of these lesions. Although characterization of imaging is often difficult due to overlapping characteristics, imaging is helpful to define which lesions should be referred for histologic examination and subsequent treatment planning. Location and density are the cardinal criteria for potential characterization on imaging. Radiologically, lesions may be radiolucent, radiopaque, or of mixed density. Additional criteria include lesion demarcation, morphology, cortical breakthrough, periosteal reaction, and adjacent soft tissue changes. Final lesion characterization is only definitive after interdisciplinary discussion and radiopathologic correlation. Correct diagnosis is obtained by a combination of the patient's age, lesion location, and clinical and radiologic presentation. It is important that all physicians use a uniform nomenclature.

Clear Cell Carcinoma of Palatal Minor Salivary Gland Harboring a Novel EWSR1-ATF1 Fusion Gene: Report of a Case and Review of the Literature

Clear cell carcinoma (CCC) is a rare low-grade malignant salivary gland carcinoma. EWSR1-ATF1 fusion has been characterized as a consistent finding in CCC, with breakpoints described between EWSR1 exon 11 and ATF1 exon 3. So far, over 100 cases of CCC harboring EWSR1 rearrangement arising from salivary gland of the oral cavity have been reported. Although EWSR1 involvement in these cases was confirmed by EWSR1 break-apart FISH indicating the translocation, sequence analysis for EWSR1-ATF1 fusion type has been reported only in three cases of CCC so far. Herein, we report a CCC case with novel EWSR1-ATF1 fusion (EWSR1 exon 15 and ATF1 exon 5) arising in minor salivary gland and review the role of the chimeric variants in some malignancies with EWSR1-ATF1 rearrangement. Current tumor was composed of the small nests of clear tumor cells and hyalized fibrous stroma. Immunohistochemically, the tumor was positive for AE1/AE3, CK5/6 and p63, negative for S100, Melan-A, SMA and CD10. After 8 months of follow-up, there are no evidence of recurrence.