EWSR1-ATF1 Fusion Gene Research Articles

EWSR1-ATF1 dependent 3D connectivity regulates oncogenic and differentiation programs in Clear Cell Sarcoma

Oncogenic fusion proteins generated by chromosomal translocations play major roles in cancer. Among them, fusions between EWSR1 and transcription factors generate oncogenes with powerful chromatin regulatory activities, capable of establishing complex gene expression programs in permissive precursor cells. Here we define the epigenetic and 3D connectivity landscape of Clear Cell Sarcoma, an aggressive cancer driven by the EWSR1-ATF1 fusion gene. We find that EWSR1-ATF1 displays a distinct DNA binding pattern that requires the EWSR1 domain and promotes ATF1 retargeting to new distal sites, leading to chromatin activation and the establishment of a 3D network that controls oncogenic and differentiation signatures observed in primary CCS tumors. Conversely, EWSR1-ATF1 depletion results in a marked reconfiguration of 3D connectivity, including the emergence of regulatory circuits that promote neural crest-related developmental programs. Taken together, our study elucidates the epigenetic mechanisms utilized by EWSR1-ATF1 to establish regulatory networks in CCS, and points to precursor cells in the neural crest lineage as candidate cells of origin for these tumors.

Malignant gastrointestinal neuroectodermal tumor: Cytologic, histologic, immunohistochemical, and molecular pitfalls

Malignant gastrointestinal neuroectodermal tumor (GNET) is a rare malignant primary gastrointestinal mesenchymal tumor which can be diagnosed via fine-needle aspiration (FNA) cytology. In the context of FNA, the diagnosis requires a cell block and the use of significant resources including immunohistochemical stains and molecular testing. The differential diagnosis of GNET includes clear cell sarcoma (CCS), gastrointestinal stromal tumor (GIST), gastric schwannoma, metastatic melanoma, malignant perivascular epithelioid cell tumor (PEComa) and granular cell tumor, among others. Here we describe a case which was initially diagnosed as malignant granular cell tumor by FNA which was later revised to GNET following the finding of an EWSR1-ATF1 fusion gene rearrangement.

Clinicopathological features and molecular genetic changes of lung salivary gland-type clear cell carcinoma

Objective: To investigate the clinicopathological features, immunophenotype, differential diagnosis, molecular genetic changes and prognosis of salivary gland-type clear cell carcinoma (CCC) of the lung. Methods: Eight cases of salivary gland-type CCC of the lung diagnosed at Fudan University Shanghai Cancer Center and Shanghai Pulmonary Hospital, China from March 2017 to December 2020 were retrieved and analyzed. The pathological sections of these cases were studied using immunohistochemical staining, fluorescence in situ hybridization (FISH), and RNA-seq fusion gene detection based on next generation sequencing technique. The patients were followed up and the relevant literature was reviewed. Results: The 8 patients included 3 males and 5 females, with age ranging from 43 to 64 years (average, 58 years). All patients underwent radical lobectomy and lymph node dissection, while only one had lymph node metastases. The eight patients were followed up for 6 to 45 months, and were all recurrence-free. Histopathologically, the tumor was mainly composed of eosinophilic and clear cells arranged in trabecular, ribbon and nest patterns. Hyalinization was often observed in the stroma around the nest. Immunohistochemical staining showed that 8/8 cases were positive for EMA and CK7; 5/8 cases were positive for p63 and p40; 4/8 cases were positive for SOX10; and the cases were all negative for S-100, SMA and calponin. EWSR1 gene fusion was detected in all cases by FISH. RNA-seq fusion gene was detected in 6 cases based on next generation sequencing. The EWSR1-ATF1 gene fusion was detected in 5 cases, among which one case also had the ATF1-SPTLC2 gene fusion. All 5 cases with EWSR1-ATF1 gene fusion showed that EWSR1 exon 12/13 fused with ATF1 exon 3. And EWSR1-CREM gene fusion was detected in one case. Conclusions: Salivary gland-type CCC of the lung is an extremely rare primary lung tumor arising from the bronchial mucosa. The diagnosis and differential diagnosis of this tumor depend on classic histomorphology, especially the auxiliary detection of EWSR1 fusion gene. The primary treatment choice of this tumor is complete surgical resection. Lymph node metastases may occur, but the overall prognosis is good.

Malignant gastrointestinal neuroectodermal tumor with BRAF mutation and a history of malignant melanoma: A case report.

Malignant gastrointestinal neuroectodermal tumors (GNETs), also called clear-cell sarcoma-like tumors of the gastrointestinal tract, are rare and highly aggressive tumors originating in the gastrointestinal tract. These tumors are generally immunohistochemically positive for S-100 protein (S-100) and SRY-related HMG-box 10 (SOX10), and often contain EWSR1-ATF1 or EWSR1-CREB1. The histological features of GNETs overlap with those of clear-cell sarcoma of the tendons and aponeuroses. However, GNETs immunohistochemically lack melanocyte-specific markers and often demonstrate positivity for CD56, synaptophysin and neuron-specific enolase. The present case reports a woman with a history of desmoplastic malignant melanoma exhibiting a BRAF mutation, which later transformed into a GNET of the small intestine with both a BRAF mutation and two subtypes of EWSR1-ATF1 fusion genes. Tumor cells were revealed to be weakly immunoreactive or negative for S-100 and SOX10, lacked markers of melanocytic differentiation and were focally positive for CD56. Combination therapy with dabrafenib mesylate and trametinib dimethyl sulfoxide proved to be temporarily effective against this tumor. The present case is relatively unique as, to the best of our knowledge, there is no case of GNET with a history of melanoma. Furthermore, there is no report of GNET exhibiting both a BRAF mutation and an EWSR1-ATF1 fusion gene. Further accumulation of similar cases is necessary to elucidate the pathological significance of this GNET having a BRAF mutation.

SURG-35. INTRACRANIAL MYXOID MESENCHYMAL TUMOR WITH EWSR1-ATF1 GENE FUSION

Abstract Intracranial myxoid mesenchymal tumors (IMMT) carrying an EWSR1-CREB gene family fusion are extremely rare and have only been identified in ten relatively recent reported cases. There is some question as to whether this is a novel entity, or a myxoid variant of angiomatoid fibrous histiocytoma (AFH), given certain histopathological similarities. Despite these similarities, the increasing number of cases reported appear to demonstrate clear histological differences that indicate IMMTs are a distinct and novel entity. Previous reports have focused on histological analysis but have lacked detailed long-term clinical follow-up and recommendations regarding treatment approach. In this case, we describe a 48-year-old female who presented with a left intraventricular mass that was identified histologically as an IMMT with an EWSR1-ATF1 gene fusion. Following initial resection, the tumor demonstrated local recurrence. Repeat resection was performed followed by immediate demonstration of local, as well as distant, tumor recurrence. Subsequent histological analysis of the tumor demonstrated a myxoid mesenchymal tumor clearly distinct from AFH. Fractionated stereotactic radiation therapy was administered following the second resection and tumor control was achieved at 1 year. This case is particularly remarkable as it is only the second reported IMMT case to occur in a middle-aged adult, with all other cases occurring in children or young adults. The two middle-aged adult cases share striking similarities in clinical presentation, including a history of breast cancer. Our findings indicate that an intracranial myxoid mesenchymal tumor is a novel and rare entity that may demonstrate rapid local and distant recurrence. Given the aggressive recurrence seen with the presented case, we recommend the treatment plan to be surgical resection followed by adjuvant radiation therapy to maintain tumor control.

Hyalinizing clear cell carcinoma of the anterior lingual salivary gland: A case report and review of the literature

Hyalinizing clear cell carcinoma (HCCC) is a low-grade epithelial tumor classified as a subtype of salivary gland carcinoma. HCCC occurs most frequently on the palate and base of the tongue. Noteworthy, HCCC arising in the anterior of the tongue is quite rare and it has yet to be fully characterized in the clinical literature. Herein, we present a case of a 59‐year‐old man with HCCC on the anterior of the tongue. A present case was confirmed by a detection of EWSR1-ATF1 fusion gene with a same breakpoint that previously reported in HCCC cases. To our knowledge, this report represents the rare case of HCCC arising in the anterior of the tongue in the literature.

Clear Cell Carcinoma of Salivary Glands Is Frequently p16 Positive: A Pitfall in the Interpretation of Oropharyngeal Biopsies.

Clear cell carcinoma (CCC) is a low-grade malignancy that commonly arises in minor salivary glands of the oropharynx and other sites. EWSR1-ATF1 gene fusions seem to be specific for this salivary neoplasm. Testing for EWSR1-ATF1 has expanded the histologic spectrum of CCC. As one important example, many CCCs have a predominantly squamous phenotype with few clear cells, a finding that can cause confusion with squamous cell carcinoma (SqCC). P16 immunohistochemical staining to determine human papillomavirus (HPV) status has become standard practice for all oropharyngeal carcinomas showing squamous differentiation. The purpose of this study was to determine whether this practice could contribute to the difficulty in distinguishing CCC from p16-positive SqCC. The authors' surgical pathology archives were searched for cases of CCC. All cases were evaluated with p16 immunohistochemistry, high-risk HPV RNA in situ hybridization (ISH), and EWSR1 gene break-apart fluorescence ISH. Sixteen CCCs were identified. All harbored an EWSR1 rearrangement. Eleven patients were women and 5 were men. They ranged in age from 30 to 85 years (mean, 58 y). The CCCs arose in the oropharynx (tongue base or tonsil) (n=8, 50%), oral cavity (n=4, 25%), and nasopharynx (n=4, 25%). Each case demonstrated clear cells, but the proportion was highly variable (10% to 90%, mean 48%), with 7 of 16 cases having <50% clear cells. Submitted diagnoses included SqCC (n=3) and mucoepidermoid carcinoma (n=2). Of the 3 patients diagnosed with SqCC, 1 was scheduled to undergo chemoradiation, and 1 had already completed chemoradiation. All 16 CCCs demonstrated p16 staining, with the percentage of p16-positive cells ranging from ≥70% (n=2), 50% to 69% (n=3), and 10% to 49% (n=11). Staining was cytoplasmic and nuclear. All cases were negative for high-risk HPV by RNA ISH. CCCs regularly show squamous features, often lack prominent clear cell changes, frequently arise in the oropharynx, and invariably show p16 staining. These features may cause confusion with SqCC, particularly HPV-related oropharyngeal SqCC. P16 staining is not to be taken as unequivocal evidence of an HPV-related SqCC, even for carcinomas showing squamous differentiation and originating in the oropharynx. Failure to recognize this pitfall could result in overly aggressive treatment of a low-grade carcinoma.

The Role of Molecular Testing in the Differential Diagnosis of Salivary Gland Carcinomas.

Salivary gland neoplasms are a morphologically heterogenous group of lesions that are often diagnostically challenging. In recent years, considerable progress in salivary gland taxonomy has been reached by the discovery of tumor type-specific fusion oncogenes generated by chromosome translocations. This review describes the clinicopathologic features of a selected group of salivary gland carcinomas with a focus on their distinctive genomic characteristics. Mammary analog secretory carcinoma is a recently described entity characterized by a t(12;15)(p13;q25) translocation resulting in an ETV6-NTRK3 fusion. Hyalinizing clear cell carcinoma is a low-grade tumor with infrequent nodal and distant metastasis, recently shown to harbor an EWSR1-ATF1 gene fusion. The CRTC1-MAML2 fusion gene resulting from a t(11;19)(q21;p13) translocation, is now known to be a feature of both low-grade and high-grade mucoepidermoid carcinomas associated with improved survival. A t(6;9)(q22-23;p23-34) translocation resulting in a MYB-NFIB gene fusion has been identified in the majority of adenoid cystic carcinomas. Polymorphous (low-grade) adenocarcinoma and cribriform adenocarcinoma of (minor) salivary gland origin are related entities with partly differing clinicopathologic and genomic profiles; they are the subject of an ongoing taxonomic debate. Polymorphous (low-grade) adenocarcinomas are characterized by hot spot point E710D mutations in the PRKD1 gene, whereas cribriform adenocarcinoma of (minor) salivary glands origin are characterized by translocations involving the PRKD1-3 genes. Salivary duct carcinoma (SDC) is a high-grade adenocarcinoma with morphologic and molecular features akin to invasive ductal carcinoma of the breast, including HER2 gene amplification, mutations of TP53, PIK3CA, and HRAS and loss or mutation of PTEN. Notably, a recurrent NCOA4-RET fusion has also been found in SDC. A subset of SDC with apocrine morphology is associated with overexpression of androgen receptors. As these genetic aberrations are recurrent they serve as powerful diagnostic tools in salivary gland tumor diagnosis, and therefore also in refinement of salivary gland cancer classification. Moreover, they are promising as prognostic biomarkers and targets of therapy.

Clear cell carcinoma of the minor salivary gland: Two cases report

Clear cell carcinoma (CCC) is a low-grade salivary gland carcinoma most frequently occurring in intraoral salivary glands. CCC is characterised by malignant cells with clear cytoplasm, can have a variety of architectural patterns, and often has prominent stromal hyalinisation. CCC has a consistent EWSR1-ATF1 gene fusion. We present two cases highlighting the potentially broad differential diagnosis and the utility of EWSR1 break-apart FISH in confirming the diagnosis. The treatment of this uncommon carcinoma includes surgical excision and radiotherapy.

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.

Tumeur neuroectodermique gastro-intestinale (GNET) : à propos d’un cas de tumeur du grêle avec métastases hépatiques

The gastro-intestinal neuroectodermal tumor (GNET) is a rare sarcoma of the digestive tract, which was recently recognised. The knowledge of the morphological, immunohistochemical and molecular diagnostic criteria is necessary to not mistake it for the metastasis of a melanoma or for another sarcoma of the digestive tract as the gastro-intestinal clear cells sarcoma or the malignant peripheral nervous system tumor (MPNST). We report the case of a 41-year-old patient with a GNET of the small intestine with hepatic metastasis. The histological examination showed a diffuse proliferation of epithelioid cells, which only express PS100. The presence EWSR1-ATF1 gene fusions with any melanocytic differentiation leads to the diagnosis of GNET.

Molecular signature of salivary gland tumors: potential use as diagnostic and prognostic marker.

Salivary gland tumors are a highly heterogeneous group of lesions with diverse microscopic appearances and variable clinical behavior. The use of clinical and histological parameters to predict patient prognosis and survival rates has been of limited utility, and the search for new biomarkers that could not only aid in a better understanding of their pathogenesis but also be reliable auxiliaries for prognostic determination and useful diagnostic tools has been performed in the last decades with very exciting results. Hence, gene rearrangements such as CRTC1-MAML2 in mucoepidermoid carcinomas have shown excellent specificity, and more than that, it has been strongly correlated with low-grade tumors and consequently with an increased survival rate and better prognosis of patients affected by neoplasms carrying this translocation. Moreover, MYB-NFIB and EWSR1-ATF1 gene fusions were shown to be specifically found in cases of adenoid cystic carcinomas and hyalinizing clear cell carcinomas, respectively, in the context of salivary gland tumors, becoming reliable diagnostic tools for these entities and potential therapeutic targets for future therapeutic protocols. Finally, the identification of ETV6-NTRK3 in cases previously diagnosed as uncommon acinic cell carcinomas, cystadenocarcinomas, and adenocarcinomas not otherwise specified led to the characterization of a completely new and now widely accepted entity, including, therefore, mammary analogue secretory carcinoma in the list of well-recognized salivary gland carcinomas. Thus, further molecular investigations of salivary gland tumors are warranted, and the recognition of other genetic abnormalities can lead to the acknowledgment of new entities and the acquirement of reliable biomarkers.

Cutaneous Clear Cell Sarcoma

Clear cell sarcoma is a unique soft tissue tumor with distinct microscopic features that include a nested or fascicular pattern of spindle cells accompanied by larger wreath-like giant cells scattered throughout. It harbors a unique EWSR1-ATF1 gene fusion secondary to a t(12;22)(q13;q12) translocation. Recently, it was reported that clear cell sarcoma can occur in the skin and mimic a broad spectrum of entities, including spindle cell melanoma. Here, we describe 3 new cases of clear cell sarcoma of the skin, all of which were confirmed molecularly. The patients, a 12-year-old boy, a 29-year-old woman, and a 60-year-old man, had cutaneous lesions on the thigh, dorsum of foot, and sole, respectively. All 3 lesions were originally considered suspicious of spindle cell melanoma. Microscopically, the lesions featured nodular proliferation centered in the dermis that consisted of discrete fascicles of spindle cell enmeshed by thin fibrous strands. Wreath-like cells were present in all cases. Tumor cells were positive for S100 protein (3 of 3 cases), melan A (2 of 3 cases), HMB 45 (1 of 3 cases) although a junctional melanocytic proliferation was seen in 1 case. Sentinel lymph node biopsy was negative in 2 patients. Follow-up was uneventful in 2 patients, whereas the other patient developed a lymph node metastasis 5 months after primary tumor excision. This study confirms that malignant dermal tumors that mimic but do not exactly replicate spindle cell melanoma should raise suspicion for cutaneous clear cell sarcoma and prompt the investigation for the confirmatory gene fusion t(12;22).

Endobronchial Pulmonary Angiomatoid Fibrous Histiocytoma

Angiomatoid fibrous histiocytoma (AFH) is a rare soft tissue neoplasm of intermediate biological potential, predominantly occurring in the extremities of children and young adults. It has only recently been reported as a primary lung tumor. We describe 2 cases arising endobronchially harboring EWSR1 gene rearrangements by fluorescence in situ hybridization and, respectively, EWSR1-CREB1 and EWSR1-ATF1 gene fusions by reverse transcription polymerase chain reaction. Histologically, both tumors showed classical features of AFH, comprising multiple nodules of bland spindle to epithelioid cells surrounded by lymphoplasmacytic inflammation and at least a partial fibrous capsule. Both tumors showed focal but strong desmin immunoreactivity, with focal pancytokeratin and epithelial membrane antigen in 1 case. The lung is now a recognized site of AFH occurrence, but tumors arising here can be associated with different gene fusions. It is important to recognize AFH in the pulmonary region, as its behavior at other sites is generally relatively indolent; however, it may be mistaken for metastatic or more aggressive primary lung tumors. It is likely that cases of AFH in the lung may have been previously missed because of their morphologic and genetic overlap with other pulmonary lesions.

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.

Mucocèle fronto-ethmoïdale

Intracranial myxoid mesenchymal tumors (IMMTs) carrying an EWSR1-CREB gene family fusion are extremely rare and have only been identified in 10 previous reports. All but one has been found in children or young adults. Although there appear to be similarities to a myxoid variant of angiomatoid fibrous histiocytoma (AFH), clear histologic differences exist that appear to distinguish IMMTs as a distinct and novel entity. Previous reports have lacked detailed long-term follow-up and recommendations regarding treatment approach.This case describes a 48-year-old woman who presented with a left intraventricular mass that was identified on histology as an IMMT with an EWSR1-ATF1 gene fusion. After initial resection, the tumor demonstrated local recurrence. Repeat resection was performed followed by immediate demonstration of local and distant tumor recurrence. Histologic analysis of the tumor demonstrated a myxoid mesenchymal tumor distinct from AFH. Fractionated stereotactic radiation therapy was administered after the second resection, and tumor control was achieved at 1 year.Intracranial myxoid mesenchymal tumor is a novel and rare entity that has been previously identified in only 10 cases. This case is particularly remarkable because it is only the second IMMT case to occur in a middle-aged adult and shares striking similarities in clinical presentation to the previously reported case. Given the aggressive recurrence seen with the presented case, we recommend the treatment plan to be surgical resection followed by adjuvant radiation therapy.

Clear Cell Sarcoma of Soft Tissue

Clear cell sarcoma (CCS) of soft tissue is a rare sarcoma with morphologic similarities to malignant melanoma but a distinct genetic background including a chromosomal translocation, t(12;22)(q13;q12), or a resultant EWSR1-ATF1 fusion gene. In addition, the tumors occurring in the gastrointestinal tract may have a variant fusion gene EWSR1-CREB1. This study analyzed the clinicopathologic and molecular genetic features of 33 CCSs of soft tissue. The patients' ages ranged from 13 to 73 years (median, 30 y), and there was a male predominance (20 males, 13 females). The tumors were located in the deep soft tissues of the extremities (N=25) or in the trunk or limb girdles (N=8). The median tumor size was 4 cm (range, 1 to 15 cm). The tumor cells were either spindle or epithelioid, and they were arranged predominantly in a short fascicular (N=19) or a solid sheetlike growth pattern (N=14). Minor histologic variations included the existence of rhabdoid cells (N=8), bizarre pleomorphic cells (N=6), alveolar structures due to loss of cellular cohesion (N=3), and a seminomalike pattern (N=2). Tumor necrosis was evident in 14 tumors, and the mitotic activity ranged from 0 to 43 mitotic figures (MF)/10 high-power fields (HPF) (mean: 4 MF/10 HPF). Immunohistochemically, the tumors were consistently positive for S-100 protein (33/33) and variably or focally for HMB45 (32/33), microphthalmia transcription factor (26/32), Melan A (23/32), CD57 (25/33), bcl-2 (30/32), synaptophysin (14/32), CD56 (7/32), epithelial membrane antigen (12/33), cytokeratin (AE1/AE3) (1/32), CD34 (3/32), c-erbB-2 (10/32), c-kit (5/32), and c-met (5/32). alpha-Smooth muscle actin, desmin, and cytokeratin (CAM5.2) were negative. Reverse transcription-polymerase chain reaction using RNA extracted from formalin-fixed, paraffin-embedded tissues demonstrated transcripts of the EWSR1-ATF1 (31/33) or EWSR1-CREB1 fusion gene (2/33). In 26 cases with available clinical information, local recurrences and metastases developed in 2 and 15 patients, respectively. Ten patients were dead of the disease, and the overall survival rate was 63% at 5 years. However, no clinicopathologic or molecular variables associated with the patients' prognosis were identified. This study confirms that CCS is an aggressive soft tissue tumor with a melanocytic phenotype and wider morphologic variations than had been generally considered. In cases with unusual histologic findings, molecular detection of the EWSR1-ATF1/CREB1 fusion genes provides critical information regarding the diagnosis of the tumor.

Clear Cell Sarcoma of Tendons and Aponeuroses: A Historical Perspective and Tribute to the Man Behind the Entity

Clear cell sarcoma of tendons and aponeuroses is a unique sarcoma initially described by Dr Franz M. Enzinger. The tumor has a proclivity to involve the tendons and aponeuroses of distal extremities of relatively young individuals and is characterized by multiple local recurrences with late metastases and a high rate of tumor deaths. Since its seminal description in 1965, there have been many studies verifying the uniqueness of this entity and probing its differentiation. Ultrastructural and immunohistochemical studies have shown melanocytic differentiation, whereas molecular genetic studies have shown cytogenetic rearrangements resulting in a EWSR1-ATF1 fusion gene that is characteristic but not entirely unique for clear cell sarcoma (similar fusion genes are also seen in angiomatoid fibrous histiocytoma). Detection of this fusion gene and the absence of BRAF gene mutations clearly distinguish clear cell sarcoma from cutaneous melanoma. Adverse prognostic factors identified to date include larger tumor size and any microscopic tumor necrosis. Surgery is the mainstay of treatment for this high grade sarcoma, with chemotherapy having little effect. Although the melanocytic differentiation of clear cell sarcoma is indisputable, its precise lineage remains unclear. Thus, clear cell sarcoma maintains the status of a unique yet enigmatic clinicopathologic entity of ever increasing complexity 40 years after its original description by an extraordinarily gifted man.