EWSR1-ATF1 Fusion Research Articles

EWSR1 translocation in primary hyalinising clear cell carcinoma of the thymus.

In thymic carcinomas, focal clear cell change is a frequent finding. In addition to a prominent, diffuse clear cell morphology, some of these carcinomas show an exuberant hyalinised extracellular matrix, and therefore probably represent a separate entity. However, a characteristic genomic alteration remains elusive. We hypothesised that, analogous to hyalinising clear cell carcinomas of the salivary gland, hyalinising clear cell carcinomas of the thymus might also harbour EWSR1 translocations. We identified nine archived cases of thymic carcinoma with focal clear cell features and two cases that showed remarkable hyalinised stroma and prominent, diffuse clear cell morphology. These two cases expressed p40 and were negative for Pax8, CD5, and CD117. Programmed death-ligand 1 was highly positive in one case (70%), and negative in the other one. EWSR1 translocation was identified in both cases of hyalinising clear cell carcinoma, and was absent in all nine carcinomas that showed clear cell features without substantial hyalinisation. In one of the EWSR1-translocated cases, a fusion between exon 13 and exon 6 of EWSR1 and ATF1, respectively was identified by next-generation sequencing. These findings suggest that the EWSR1 translocation and possibly the EWSR1-ATF1 fusion might be unifying genomic alterations for thymic clear cell carcinomas with prominent hyalinised stroma, for which we propose the term 'hyalinising clear cell carcinoma of the thymus'. Because the immunophenotype is unspecific, testing for the EWSR1 translocation might be helpful in discriminating this entity from other thymic neoplasms or metastases, in particular those with clear cell change.

Detection of specific gene rearrangements by fluorescence in situ hybridization in 16 cases of clear cell sarcoma of soft tissue and 6 cases of clear cell sarcoma-like gastrointestinal tumor

BackgroundClear cell sarcoma of soft tissue (CCSST) and clear cell sarcoma-like gastrointestinal tumor (CCSLGT) are malignant mesenchymal tumors that share some pathological features, but they also have several different characteristics. They are well known to express chimeric fusions of Ewing sarcoma breakpoint region 1 (EWSR1) and cAMP response element-binding protein (CREB) family members; namely, EWSR1-activating transcription factor 1 (ATF1) and EWSR1-CREB1. In addition, recent studies have suggested the presence of other fusions.MethodsWe used fluorescence in situ hybridization to detect specific rearrangements including EWSR1, ATF1, CREB1, and cAMP response element modulator (CREM) in 16 CCSST and 6 CCSLGT cases. We also used reverse transcription polymerase chain reaction (RT-PCR) to detect specific chimeric fusions of EWSR1-ATF1 and EWSR1-CREB1 using fresh tumor samples in available cases.ResultsA total of 15 of 16 CCSST cases (93.8%) had EWSR1 rearrangement, of which 11 (68.8%) also had ATF1 rearrangement, suggestive of the presence of EWSR1-ATF1 fusions. One CCSST case (6.3%) was found to have EWSR1 and CREM rearrangements, and 4 of 6 CCSLGT cases (66.7%) had EWSR1 rearrangement, of which 2 (33.3%) showed ATF1 rearrangement and the other 2 cases (33.3%) showed CREB1 rearrangement. These cases most likely had EWSR1-ATF1 and EWSR1-CREB1 fusions, respectively. RT-PCR was performed in 8 available cases, including 6 CCSSTs and 2 CCSLGTs. All CCSSTs showed EWSR1-ATF1 fusions. Among the 2 CCSLGT cases, one had EWSR1-ATF1 fusion and the other had EWSR1-CREB1 fusion.ConclusionsRearrangements of EWSR1 and ATF1 or EWSR1-ATF1 fusion were predominantly found in CCSST, whereas those of EWSR1 and CREB1 or EWSR1-CREB1 tended to be detected in CCSLGT. A novel CREM fusion was also detected in a few cases of CCSST and CCSLGT. The cases in which EWSR1 rearrangement was detected without definitive partner genes should be considered for the presence of CREM rearrangement.

Clear Cell Odontogenic Carcinoma: Occurrence of EWSR1-CREB1 as Alternative Fusion Gene to EWSR1-ATF1.

Clear cell odontogenic carcinoma (CCOC) is a rare, low-grade malignant epithelial neoplasm, occurring in the jawbones, mainly affecting the mandible of elderly patients. In addition to hyalinizing clear cell carcinoma of the salivary gland, it is one of the epithelial neoplasms known to harbor an EWSR1-ATF1 fusion. Therefore, a link between these tumors seems plausible. We describe six cases of CCOC showing EWSR1 rearrangements, with two cases being positive for the ATF1 partner gene using FISH analysis. In one case, an EWSR1-CREB1 fusion was identified using RT-PCR, which we report for the first time in this tumor type. The other three cases investigated by FISH were negative for ATF1, CREB1 and CREB3L2. In conclusion, our data show that EWSR1-CREB1 is an alternative fusion gene to EWSR1-ATF1 in CCOC.

Hyalinizing clear cell carcinoma of the bronchial glands: presentation of three cases and pathological comparisons with salivary gland counterparts and bronchial mucoepidermoid carcinomas

AbstractHyalinizing clear cell carcinoma of the bronchial glands is a very rare tumor. Since only five reports describing six tumors have been published to date, only a little is known about specific histologic findings and clinical features. Because of its rarity, hyalinizing clear cell carcinoma has not been described in the latest WHO classification of pulmonary tumors yet. Here we present three cases of bronchial hyalinizing clear cell carcinomas, confirmed by both fluorescence in situ hybridization (FISH) and RT-PCR, focusing on histologic and immunohistochemical characteristics in a comparison with three cases of salivary gland origin. In addition, we compared immunohistochemical features with bronchial mucoepidermoid carcinoma, a lesion that needs to be taken into account in differential diagnosis of hyalinizing clear cell carcinoma. All our bronchial hyalinizing clear cell carcinoma cases were surgically resected. Histologically, tumor cells showed clear to eosinophilic cytoplasm with hyalinizing stroma in various proportions, resembling those of salivary gland origin. Immunohistochemically, tumor cells were positive for CK7, CK5/6, p40, p63, and ATF1, while they were negative for TTF1, Napsin A, HMB45, and SOX10. The CK5/6 staining pattern varied in mucoepidermoid carcinomas, while that of hyalinizing clear cell carcinoma was uniformly positive. FISH revealed EWSR1-ATF1 fusion, and RT-PCR with sequencing confirmed specificity of the chimeric gene for hyalinizing clear cell carcinoma. Clinically, bronchial hyalinizing clear cell carcinoma was characterized by occurrence in the fourth to sixth decades, no link with smoking history, and a predilection for the right lung, in line with previous reports. In summary, our study confirmed that the bronchial hyalinizing clear cell carcinoma is a histologically and genetically identical tumor to that of salivary gland origin, and that gene rearrangement analysis can play a critical role in distinction from mucoepidermoid carcinoma.

Primary paranasal sinus hyalinizing clear cell carcinoma: a case report

BackgroundHyalinizing clear cell carcinoma (HCCC) is a rare low-grade tumour of salivary glands that was first described as a distinct entity in 1994 by Milchgrub et al. EWSR1-ATF1 fusion was found to be specific for this tumour. The majority of the reported cases of HCCC arise from minor salivary glands within the oral cavity. Primary HCCC of the paranasal sinus is extremely uncommon. To our knowledge, only three cases have been reported in the English literature. Herein, we present a case of HCCC of the posterior ethmoid/maxillary sinus.Case presentationA 63-year-old lady who presented with a long history of epistaxis. CT scan revealed a destructive mass in the left ethmoid/posterior maxillary sinus extending to the nasal cavity. Surgical excision was done and microscopic evaluation showed a tumour composed mainly of nests of clear epithelial cells separated by fibrocellular and hyalinized septa with extensive bone destruction. The tumour cells expressed CK5/6, EMA and p63 immunohistochemically but were negative for S100 protein, PAX-8, RCC and CK7. Sinonasal renal cell–like adenocarcinomas, myoepithelial carcinoma and metastatic renal cell carcinoma were excluded by radiological and immunohistochemical studies. Fluorescence in situ hybridization analysis revealed an EWSR1 gene rearrangement. Postoperative radiation was administrated and the patient did not show recurrence or distant metastasis 4 months after the surgery.ConclusionHead and neck region have many tumours that demonstrate clear cell changes on histology. Thus, the differential diagnosis for HCCC is wide. Awareness of this rare entity and the possibility of it is arising in unusual location is necessary. EWSR1-AFT1 fusion, a consistent finding in HCCC, can be used to confirm the diagnosis.

Establishment and characterization of a clear cell odontogenic carcinoma cell line with EWSR1-ATF1 fusion gene

ObjectiveClear cell odontogenic carcinoma (CCOC) is a rare malignant odontogenic tumor (MOT) characterized by sheets and lobules of vacuolated and clear cells. To understand the biology of CCOC, we established a new cell line, CCOC-T, with EWSR1-ATF1 fusion gene from a mandible tumor with distant metastasis and characterized this cell line. Materials and methodsTo detect the EWSR1-ATF1 fusion gene, we used three CCOC cases, including the present case, by RT-PCR and FISH analysis. We characterized established CCOC-T cells by checking cell growth, invasion and the expression of odontogenic factors and bone-related factors. Moreover, the gene expression profile of CCOC-T cells was examined by microarray analysis. ResultsHistologically, the primary tumor was comprised of cords and nests containing clear and squamoid cells separated by fibrous septa. In addition, ameloblastomatous islands with palisaded peripheral cells were observed, indicating probable odontogenic origin. This tumor expressed the fusion gene EWSR1-ATF1, which underlies the etiology of hyalinizing clear cell carcinoma (HCCC) and potentially that of CCOC. We found a breakpoint in the EWSR1-ATF1 fusion to be the same as that reported in HCCC. Established CCOC-T cells grew extremely slowly, but the cells showed highly invasive activity. Moreover, CCOC-T cells expressed bone-related molecules, odontogenic factors, and epithelial mesenchymal transition (EMT)-related molecules. ConclusionTo the best of our knowledge, this is the first report on the establishment of a CCOC cell line. CCOC-T cells serve as a useful in vitro model for understanding the pathogenesis and nature of MOT.

Reevaluation of MAML2 fusion–negative mucoepidermoid carcinoma: a subgroup being actually hyalinizing clear cell carcinoma of the salivary gland with EWSR1 translocation

Hyalinizing clear cell carcinoma (HCCC) is a rare salivary gland tumor with a specific EWSR1-ATF1 fusion gene and can have mucin production. Mucoepidermoid carcinoma (MEC) with a clear cell component is its morphologic mimic. Using MAML2 fluorescence in situ hybridization (FISH), a total of 49 MEC cases were separated into MAML2 fusion-positive (32 cases) and MAML2 fusion-negative groups (17 cases). This study used EWSR1 FISH to investigate MAML2 fusion-negative cases to identify previously unrecognized HCCC. Among 17 MAML2 fusion-negative cases, 3 had rearrangement of the EWSR1 gene and were reclassified as HCCC. Including 5 previously diagnosed HCCC cases, these 8 HCCC cases had a male-to-female ratio of 1:7, and most (7/8) tumors arose from oral minor salivary glands in the oral cavity (tongue base and palate). EWSR1-ATF1 fusion was confirmed by FISH in all 8 HCCC cases. The histologic features between genetically confirmed HCCC and MEC were compared. HCCC was significantly associated with minor salivary gland involvement, a discrepancy between low-grade cytology and intermediate- to high-grade histology using the MEC grading system, and absence of both epidermoid cells with abundant cytoplasm and goblet cells lining cysts or forming clusters. Clear cells and a hyalinized stroma were not specific for HCCC. HCCC may be erroneously classified as MEC because clear cells may be a minor histologic component and mucin production is not uncommon. Previously diagnosed MEC cases should be reevaluated, especially those arising from minor salivary glands or without MAML2 fusion. Careful histologic evaluation with supporting molecular testing can facilitate pathologic diagnoses.

Molecular genetics, diagnosis and management of clear cell sarcoma of hand

Synonyms: Clear cell sarcoma of soft tissue, Clear cell sarcoma of the tendons and aponeuroses, malignant melanoma of the soft parts. Background: Rodriguez-Martin, Ortiz-Cruz, Del Rio, Vivanco, & Lopaz-Amor in 2011 stated “Clear cell sarcoma is a high-grade soft tissue sarcoma seen in adolescents and young adults, with melanosytic differentiation typically involving tendons and aponeuroses”. Clear cell sarcoma of soft tissue (CCSST) was originally described by Dr. Franz M. Enzinger in 1965 as a distinct entity of tumors arising from tendons and aponeuroses in young adults. Clear cell sarcoma (CCS) of soft tissue is a rare sarcoma with morphologic similarities to malignant melanoma. They are characterized by a distinct genetic background including a chromosomal translocation t(12;22)(q13;q12), or a resultant EWSR1-ATF1 fusion gene. The lower limbs are involved more commonly. Clear cell sarcoma has been reported in other tissues such as bone, colon and gastrointestinal tract. The clear cell sarcoma that occurs in relation to the gastrointestinal tract has a variant fusion gene EWSR1-CREB1 and they are re-designated as gastrointestinal neuroectodermal tumor (GNET). Material and method: A 21 years old female with a chronic recurrent swelling of the left mid finger was diagnosed as epithelioid sarcoma on histopathological examination. Immunohistochemistry was done with basic tumor markers panel and a diagnosis of clear cell sarcoma was confirmed. Result: Immunohistochemistry staining is used for sub-typing of the tumor, predicts the prognosis of the tumor and also the response to the specific type of therapy.

Whole-exome sequencing identifies a somatic missense mutation of NBN in clear cell sarcoma of the salivary gland.

Clear cell sarcoma (CCS) is a rare, low-grade carcinoma commonly located in the distal extremities of young adults involving tendons and aponeuroses. CCS is characterized by its poor prognosis due to late diagnosis, multiple local recurrence, propensity to late metastases, and a high rate of tumor-related mortality. The genetic cause for CCS is thought to be EWSR1 gene translocation. However, CCS lacking a translocation may have other, as yet uncharacterized, genetic mutations that can cause the same pathological effect. A combination of whole‑exome sequencing and Sanger sequencing of cancer tissue and venous blood from a patient diagnosed with CCS of the salivary gland revealed a somatic missense mutation, c.1061C>T (p.P354L), in exon9 of the Nibrin gene (NBN). This somatic missense mutation led to the conversion of proline to leucine (p.P354L), resulting in deleterious effects for the NBN protein. Multiple-sequence alignments showed that codon354, where the mutation (c.1061C>T) occurs, is located within a phylogenetically conserved region. In conclusion, we here report a somatic missense mutation c.1061C>T (p.P354L) in the NBN gene in a patient with CCS lacking an EWSR1-ATF1 fusion. Our findings broaden the genotypic spectrum of CCS and provide new molecular insight that should prove useful in the future clinical genetic diagnosis of CCS.

Angiomatoid fibrous histiocytoma: comparison of fluorescence in situ hybridization and reverse transcription polymerase chain reaction as adjunct diagnostic modalities.

Angiomatoid fibrous histiocytoma (AFH) is a rare soft tissue neoplasm of intermediate biologic potential and uncertain differentiation, most often arising in the extremities of children and young adults. Although it has characteristic histologic features of a lymphoid cuff surrounding nodules of ovoid cells with blood-filled cystic cavities, diagnosis is often difficult due to its morphologic heterogeneity and lack of specific immunoprofile. Angiomatoid fibrous histiocytoma is associated with recurrent chromosomal translocations, leading to characteristic EWSR1-CREB1, EWSR1-ATF1, and, rarely, FUS-ATF1 gene fusions; fluorescence in situ hybridization (FISH), detecting EWSR1 or FUS rearrangements, and reverse transcription-polymerase chain reaction (RT-PCR) for EWSR1-CREB1 and EWSR1-ATF1 fusion transcripts have become routine ancillary tools. We present a large comparative series of FISH and RT-PCR for AFH. Seventeen neoplasms (from 16 patients) histologically diagnosed as AFH were assessed for EWSR1 rearrangements or EWSR1-CREB1 and EWSR1-ATF1 fusion transcripts. All 17 were positive for either FISH or RT-PCR or both. Of 16, 14 (87.5%) had detectable EWSR1-CREB1 or EWSR1-ATF1 fusion transcripts by RT-PCR, whereas 13 (76.5%) of 17 had positive EWSR1 rearrangement with FISH. All 13 of 13 non-AFH control neoplasms failed to show EWSR1-CREB1 or EWSR1-ATF1 fusion transcripts, whereas EWSR1 rearrangement was present in 2 of these 13 cases (which were histopathologically myoepithelial neoplasms). This study shows that EWSR1-CREB1 or EWSR1-ATF1 fusions predominate in AFH (supporting previous reports that FUS rearrangement is rare in AFH) and that RT-PCR has a comparable detection rate to FISH for AFH. Importantly, cases of AFH can be missed if RT-PCR is not performed in conjunction with FISH, and RT-PCR has the added advantage of specificity, which is crucial, as EWSR1 rearrangements are present in a variety of neoplasms in the histologic differential diagnosis of AFH, that differ in behavior and treatment.

Angiomatoid fibrous histiocytoma of the pulmonary artery: a multidisciplinary discussion

Angiomatoid fibrous histiocytoma (AFH) is a rare neoplastic disease usually occurring in the dermis or subcutis of the extremities of young adults or children. Although sporadic cases in deep soft tissue and visceral organs have been reported, we present here the first description of AFH developing in a large artery. Paraffin sections of the surgical specimen were stained with haematoxylin and eosin, and immunohistochemistry was performed (CKAE1/AE3, EMA, CD34, p63, CD38, smooth muscle actin, and desmin). In addition, FISH and RT-PCR were applied in order to check for EWRS rearrangement. The histomorphological features, and FISH analysis revealing rearrangement of EWSR, indicated the definitive diagnosis of AFH. RT-PCR confirmed EWSR rearrangement, and detected an EWSR1-ATF1 fusion transcript. A thoracic location of AFH has not been reported until very recently, and shares a differential diagnosis with diverse neoplasms, including spindle cell carcinoma and low-grade sarcoma. We describe the first reported case of thoracic AFH arising in a large vessel, and highlight distinctive histological and molecular features.

Envisioning the Next WHO Head and Neck Classification

The next WHO classification should abandon "salivary duct carcinoma"; conventional salivary duct carcinoma should be classified as "high-grade salivary duct carcinoma". Low-grade salivary duct carcinoma should replace the current nosology of "low-grade cribriform cystadenocarcinoma". Cystadenocarcinoma should be classified with the descriptor "Not Otherwise Specified" and should be considered an exclusionary diagnostic category. On the other hand, "Not Otherwise Specified" does not fit for hyalinizing clear cell carcinoma (HCCC). The EWSR1-ATF1 fusion is specific for HCCC within the context of salivary neoplasia. We recommend adding "hyalinizing" even though this feature is not present in all cases; the benefit of which is the mental association with a salivary clear cell malignancy. Sinonasal Renal Cell-like Adenocarcinoma (SNRCLA) is a distinct clear cell neoplasm and should be added to the next WHO classification. Future studies will bear out whether SNRCLA is even a low-grade carcinoma, or may be reclassified as "adenoma". Lastly, the next WHO monograph should include the Risk Model in the general introductory statements on oral squamous cell carcinoma, under a subheading of "Histological Prognosticators". The positive predictive value for developing locoregional recurrence in patients with low-stage oral cavity squamous carcinoma (OSCC) and "worst pattern of invasion type-5" (WPOI-5) is 42 %. Low-stage high-risk OSCC with a combination of features other than WPOI-5 is associated with 32 % likelihood for locoregional progression. WPOI-5 also predicts occult metastatic disease (p = 0.0001, Chi squared, 2 DF). Thus the Risk Model can also be used to make decisions regarding staged elective neck dissections.

Angiomatoid fibrous histiocytoma: clinicopathological and molecular characterisation with emphasis on variant histomorphology

AimsAngiomatoid fibrous histiocytoma (AFH) is histologically typified by nodules of histiocytoid spindle cells with pseudoangiomatoid spaces, fibrous pseudocapsules and lymphocytic cuffs. The principal goal was to expand the spectrum of...

A rare case of clear cell sarcoma with 4 types of EWSR1-ATF1 fusions detected not in primary site but in metastatic site

Clear cell sarcoma is a unique tumor which has EWSR1-ATF1 or EWSR1-CREB1 fusion. Several patterns of EWSR1-ATF1 fusion are observed in clear cell sarcoma. Since type 5–7 fusions were reported recently, they are classified as type 1–7. We examined EWSR1-ATF1 and EWSR1-CREB1 fusions in a single case of clear cell sarcoma with lung metastasis in a 36-year-old Japanese man. As a result, we found only type 1 EWSR1-ATF1 fusion in the primary site, but 4 types of EWS-ATF1 fusion (type 1, 2, 5, 6) were detected in the metastatic site. These 4 types of fusion were completely identical to the recent report, but the case had the same fusion patterns in both primary and metastatic sites. In our case, increased splicing activity in the EWSR1-ATF1 fusion might be acquired at the metastatic site. There is another possibility that metastasis might develop through the increased splicing activity in the fusion.

An Update on Salivary Gland Pathology

Over the past few decades, salivary gland tumor pathology has evolved. This includes recognition of newly defined entities as well as reclassification of other salivary gland tumors [1]. The development of genetic tests have shown that some salivary gland tumors have genetic abnormalities which are specific to a histologic type such as MECT1–MAML2 gene fusion in mucoepidermoid carcinoma and PLAG1 or HMGA2 gene translocation in pleomorphic adenoma. Immunohistochemical studies have aided in both the diagnosis and prognosis of salivary gland tumors. High Ki67 is correlated with poor overall survival in mucoepidermoid carcinoma, acinic cell carcinoma and adenoid cystic carcinoma. High MUC1 in mucoepidermoid carcinoma is associated with higher grade and high recurrence while MUC4 is associated with a lower grade tumor and longer disease free survival. The finding of androgen receptors in salivary duct carcinoma has led to new therapies as these tumors are shown to be responsive to androgen deprivation therapy. Newly described salivary gland entities in the past 20 years include both benign (sclerosing polycystic adenosis, sialolipoma) and malignant (cribriform adenocarcinoma of the tongue, mammary analogue secretory carcinoma) tumors [2]. Newly recognized histologic variants of well-known salivary gland tumors have been reported, to include salivary-duct carcinoma, acinic cell carcinoma and epi-myoepithelial carcinoma [1, 2]. In view of these dramatic changes, the Head and Neck Pathology journal leadership are particularly pleased to bring together an international panel of experts in salivary gland pathology as contributors to this special issue. Guest editors, Michal Michal, M.D, Ph.D and Alena Skalova, M.D, Ph.D have developed a special issue on salivary gland pathology that encompasses the advances in classification, genetics and other emerging concepts in the field. This update on salivary gland pathology is divided into four groups: tumors associated with molecular genetics; high grade and low grade salivary gland carcinomas; histologic variants of benign and malignant salivary gland tumors; and non-neoplastic lesions. Dr. Michal and colleagues first reported on cribriform adenocarcinoma of the tongue in 1999 and since then other pathologists have recognized this rare entity not only in the tongue but also in other minor salivary gland locations. Dr. Michal describes the characterization of this tumor including immunohistochemical and molecular studies. Dr. Goran discusses the salivary gland neoplasms that have fusion oncogenes and the clinical impact of these findings. Dr. Weinreb focuses on hylanizing clear cell carcinoma and in particular the EWSR1-ATF1 fusion set within a discussion of the differential diagnosis. Dr. Skalova rounds out the section on molecular-defined tumors with the features of mammary analogue secretory carcinoma, originally described by Dr. Skalova in 2010. Dr. Nagao discusses high grade transformation and dedifferentiation in both adenoid cystic carcinoma and acinic cell carcinoma. Newly recognized histologic variants of the high grade salivary duct carcinoma such as mucin-rich variant and sarcomatoid variant are described by Dr. Simpson. In contrast to this high grade salivary gland malignancy, Dr. Perez-Ordonez discusses low-grade salivary duct carcinoma and other intraductal carcinomas. Dr. DiPalma provides a review of carcinoma ex pleomorphic adenoma with special emphasis on the evolution of this neoplasm with distinction of the in situ category from minimally invasive and frankly invasive tumors. Recent studies have broadened the histologic range of epithelial-myoepithelial carcinoma and Dr. Seethala describes some of the new variants of this tumor. Dr. Gnepp reviews unusual mucinous tumors of salivary glands and Dr. Agaimy focuses on fat-containing salivary gland neoplasms. Dr. Petersson discusses a rare salivary gland entity: sclerosing polycystic adenosis, first characterized in 1996. We hope these stimulating discussions on common and rare salivary gland lesions will provide our readership with new tools to enable improved diagnosis.

Hyalinizing Clear Cell Carcinoma of Salivary Gland: A Review and Update

Hyalinizing clear cell carcinoma (HCCC) is a rare minor salivary gland tumor made up of clear cells and forming cords and nests in a hyalinized stroma. The overall outcome is excellent with only occasional metastatic spread. HCCC has a wide differential diagnosis including other clear cell-containing tumors, such as epithelial-myoepithelial carcinoma, mucoepidermoid carcinoma, and myoepithelial carcinoma. HCCC is currently classified as a "clear cell adenocarcinoma" by the AFIP and as "clear cell carcinoma, not otherwise specified (NOS)" by the World Health Organization (WHO). It is considered by the WHO to be a diagnosis of exclusion. Since the original description in 1994, there have been few new insights into HCCC, until recently. Dardick re-examined the features of HCCC, including the original electron microscopic images, and concluded that HCCC is a squamous lesion, at odds with the above nomenclature. Bilodeau et al. recently showed that this tumor essentially cannot be separated reliably from clear cell odontogenic carcinoma (CCOC) except by location. Antonescu et al. recently identified a consistent EWSR1-ATF1 fusion in HCCC. Bilodeau et al. subsequently argued a link between these two entities, with evidence of similar EWSR1 and ATF1 rearrangements in CCOC. This molecular signature is not present in other clear cell mimics. Cases with recurrence, metastasis, high-grade features and other alternative morphologies or presentations have also been seen and proven by molecular analysis to be HCCC. In the molecular era, HCCC can no longer be seen as a diagnosis of exclusion. It is neither an adenocarcinoma nor a "not otherwise specified" tumor, as the AFIP and WHO currently classify it. This review provides an in-depth look at the current state of knowledge of HCCC from morphology to molecular features. New developments and personal insights are provided that help identify and properly classify this lesion.

What the EWSR1-ATF1 Fusion has Taught Us About Hyalinizing Clear Cell Carcinoma

Hyalinizing clear cell carcinoma (HCCC) is a unique low-grade tumor composed of cords and nests of clear cells in a hyalinized stroma that was first reported by Milchgrub et al. It was recognized as a separate entity from clear cell variants of epithelial-myoepithelial carcinoma, myoepithelial carcinoma and mucoepidermoid carcinoma. HCCC is included in a long list of clear cell-containing tumors of salivary gland, as well as odontogenic tumors and metastases (renal cell carcinoma). Up until now, it has been considered a diagnosis of exclusion, despite its very distinctive appearance, and labeled as "not otherwise specified" by the World Health Organization. The emergence of molecular data in salivary gland tumors, including HCCC now allow for a more rigorous appraisal of its spectrum. The EWSR1-ATF1 fusion has proven the concept of a "mucinous HCCC" and removes mucin as an exclusion criterion for this tumor. It has also proven a genetic link between clear cell odontogenic carcinoma and HCCC. Molecularly-proven cases have also highlighted variant morphologies and shown that cases with overt squamous differentiation are true HCCC. This gives further weight to the classification of this tumor as squamous or adenosquamous in differentiation and as a specific entity rather than an "NOS" tumor.

Primary pulmonary myxoid sarcoma with EWSR1‐CREB1 fusion, resembling extraskeletal myxoid chondrosarcoma: Case report with a review of Literature

Reported herein is an extremely rare case of primary pulmonary myxoid sarcoma (PPMS). A 31-year-old man presented with a 2.7 cm-sized pulmonary tumor surrounded by capsule-like fibrosis. The patient has been free of disease for 5.8 years after surgery. This tumor focally showed endobronchial features, and consisted of reticular cords of oval, short spindle, or polygonal cells with swollen vesicular nuclei accompanied by an abundant myxoid stroma, closely resembling extraskeletal myxoid chondrosarcoma. Tumor cells were diffusely positive for vimentin and focally positive for epithelial membrane antigen, but were negative for cytokeratin, TTF-1, Napsin A, S-100 protein, CD34, desmin, smooth-muscle actin, CD10, p63, calponin, h-caldesmon, c-kit, HMB-45, synaptophysin, or glial fibrillary acid protein. Our reverse transcription-polymerase chain reaction using the formalin-fixed, paraffin-embedded tumor tissues detected EWSR1-CREB1 fusion transcript, but could not demonstrate EWSR1-ATF1 fusion or EWSR1/TAF15/TFG-NR4A3 fusion. These findings indicate that the current tumor is an additional case of PPMS with EESR1-CREB1 fusion, recently reported by Thway et al. Some cases of PPMS can behave in an indolent manner.

Progress in salivary gland pathology: new entities and selected molecular features

Salivary gland neoplasms are a morphologically heterogeneous group of lesions that are occasionally diagnostically challenging. This review describes the clinicopathologic features of a selected group of salivary gland carcinomas with a focus on their distinctive molecular characteristics. Mammary analogue secretory carcinoma is a recently described entity characterized by a t(12;15)(p13;q25) translocation with formation of an ETV6–NTRK3 fusion gene. Hyalinizing clear cell carcinoma is a low-grade tumour with infrequent nodal and distant metastasis, recently shown to harbour an EWSR1–ATF1 fusion gene. The MECT1–MAML2 fusion gene resulting from a t(11;19)(q21;p13) translocation, is now known to be a feature of both low and high-grade mucoepidermoid carcinomas which has been associated with improved survival. A recently detected t(6;9)(q22-23;p23-34) translocation resulting in the MYB–NFIB fusion gene has been identified in at least a subset of adenoid cystic carcinomas. Evidence that increased MYB expression may be significantly correlated with poor survival is emerging.

Deep intronic point mutations of the KIT gene in a female patient with cutaneous clear cell sarcoma and her family

Clear cell sarcoma (CCS) of tendons and aponeuroses is an aggressive neoplasm that is characterized by a pathognomonic translocation, t(12;22)(q13;q12), resulting in an EWSR1-ATF1 chimeric gene. We report for the first time a female patient with CCS exhibiting both EWSR1-ATF1 fusion transcripts and hereditary homozygous point mutations in introns 11 and 16 of the KIT gene. Her parents and two brothers each had heterozygous point mutations in intron 11 or intron 16 of the KIT gene. The functional significance of these germline deep intronic point mutations and their relationship to the pathogenesis of CCS are unclear. Future studies investigating KIT intron mutations in a larger cohort of CCS patients are warranted.