Molecular diagnosis of clear cell sarcoma: detection of EWS-ATF1 and MITF-M transcripts and histopathological and ultrastructural analysis of 12 cases

Genetics of rare mesenchymal tumors: implications for targeted treatment in DFSP, ASPS, CCS, GCTB and PEComa

Soft tissue and bone sarcomas comprise a heterogeneous group of mesenchymal tumors that include roughly 130 distinct diagnostic entities. Many of them are exceptionally rare, with only few cases diagnosed worldwide each year. Development of novel targeted treatment in this group of tumors is of special importance since many sarcoma subtypes are resistant to conventional chemotherapy and the effective therapeutic options are limited. In this review we aim to discuss the molecular implications for targeted therapy in selected rare soft tissue and bone sarcoma subtypes, including dermatofibrosarcoma protuberans (DFSP), alveolar soft part sarcoma (ASPS), clear cell sarcoma (CCS), giant cell tumor of bone (GCTB) and perivascular epithelioid cell neoplasms (PEComas). This article is part of a Directed Issue entitled: Rare cancers.

Clear cell sarcoma of soft tissue: a retrospective review and analysis of 31 cases treated at Istituto Ortopedico Rizzoli

INTRODUCTION

Clear cell sarcoma (CCS) of soft tissue is a rare melanocytic soft tissue sarcoma with different cytogenetic and natural history than that of melanoma. Objective of this study was to determine outcome predictors in patients treated in our Institute. This objective included the effectiveness of surgical intervention and disease progression after surgery.

MATERIALS AND METHODS

Thirty-one patients were diagnosed at our institute with clear cell sarcoma through tissue pathology and immunohistochemistry. Patients received multimodality treatment (surgery, radiotherapy and chemotherapy). Five-year survival rates and prognostic predictors were determined.

RESULTS

Sixteen patients were males and 15 females with a median age of 37 years (8-72-years). Twenty-eight tumors were located in extremities and 3 in the trunk area. Eight patients had metastases at their first presentation (6 local lymph nodes and 2 pulmonary metastases). Five and ten-year disease-specific survival rates were 56% and 41%. Two-year disease-specific survival rates for lymph node and pulmonary metastasis groups were 40% and 0%. All metastatic patients died within 5 years follow-up. Five and ten-year disease-specific survival rates for localized tumor cases were 72% and 53%. Male gender, less than 30-years of age, trunk tumor location and size greater than 5 cm were poor prognostic factors according to univariate analysis. Tumor location in the trunk was the only negative prognostic determinant in multivariate model.

CONCLUSIONS

Although surgical treatment may be beneficial for tumors without systemic involvement, new chemotherapeutic agents and molecular targeted therapy should be implemented to improve the oncologic outcome in both early and late stage disease.

Clear cell sarcoma of tendons and aponeuroses of the parapharyngeal space: an unusual localization of a rare tumor (a case report and review of the literature)

The clear cell sarcoma of tendons and aponeuroses (CCSTA) is a rare soft tissue sarcoma in the head and neck region and parapharyngeal space. Over 95% of CCSTAs present in the extremities, with the head and neck region (1.9%) being an unusual site. This study presents an additional case of CCSTA of the head and neck region involving the parapharyngeal space in a 48-year-old men and review of the literature on CCSTA.

Non-antiepileptic drugs for trigeminal neuralgia

BACKGROUND

Trigeminal neuralgia was defined by the International Association for the Study of Pain as a sudden, usually unilateral, severe, brief, stabbing recurrent pain in the distribution of one or more branches of the fifth cranial nerve. Standard treatment is with anti-epileptic drugs. Non-antiepileptic drugs have been used in the management of trigeminal neuralgia since the 1970s. This is an update of a review first published in 2006 and previously updated in 2011.

OBJECTIVES

To systematically review the efficacy and tolerability of non-antiepileptic drugs for trigeminal neuralgia.

SEARCH METHODS

On 20 May 2013, for this updated review, we searched the Cochrane Neuromuscular Disease Group Specialized Register, CENTRAL (2013, Issue 4), MEDLINE (January 1966 to May 2013), EMBASE (January 1980 to May 2013), LILACS (January 1982 to May 2013) and the Chinese Biomedical Retrieval System (1978 to May 2013). We searched clinical trials registries for ongoing trials.

SELECTION CRITERIA

We included double-blind, randomised controlled trials in which the active drug was used either alone or in combination with other non-antiepileptic drugs for at least two weeks.

DATA COLLECTION AND ANALYSIS

Two authors decided which trials fitted the inclusion criteria and independently graded risk of bias. We assessed the quality of the evidence according to the GRADE criteria for this update.

MAIN RESULTS

In this 2013 update, we updated the searches, but identified only two new ongoing studies. The review includes four trials involving 139 participants. The primary outcome measure in each was pain relief. Three trials compared one of the oral non-antiepileptic drugs tizanidine, tocainide or pimozide with carbamazepine. The quality of evidence for all outcomes for which data were available was low. In a trial of tizanidine involving 12 participants (one dropped out due to unrelated disease), one of five participants treated with tizanidine and four of six treated with carbamazepine improved (risk ratio (RR) 0.30, 95% confidence interval (CI) 0.05 to 1.89). Few side effects were noted with tizanidine. For pimozide, there was evidence of greater efficacy than carbamazepine at six weeks. Up to 83% of participants reported adverse effects but these did not lead to withdrawal; the report did not provide comparable data for carbamazepine. Limited data meant that we could not assess the effects of tocainide; however, data from non-randomised studies (not included in this review) indicate that serious haematological adverse events can occur. A trial involving 47 participants compared 0.5% proparacaine hydrochloride eyedrops with placebo but did not show any significant benefits, again according to low-quality evidence. The report did not mention adverse events. The proparacaine trial was at low risk of bias; the other trials were at unclear risk of bias overall.

AUTHORS' CONCLUSIONS

There is low-quality evidence that the effect of tizanidine is not significantly different than that of carbamazepine in treating trigeminal neuralgia. Pimozide is more effective than carbamazepine, although the evidence is of low quality and the data did not allow comparison of adverse event rates. There is also low-quality evidence that 0.5% proparacaine hydrochloride eye drops have no benefit over placebo. Limitations in the data for tocainide prevent any conclusions being drawn. There is insufficient evidence from randomised controlled trials to show significant benefit from non-antiepileptic drugs in trigeminal neuralgia. More research is needed.

Clinicopathological features, diagnosis and treatment of clear cell sarcoma/melanoma of soft parts

Clear cell sarcoma of tendons and aponeuroses is a rare, high grade malignant soft tissue tumor resembling melanoma and soft tissue sarcomas. Clinical and Imaging Presentation: The median age at presentation is 27 years and the most common location are the foot and the ankle. MR imaging typically shows a benign looking, well defined, homogenous mass; on T1-weighted MR images, it is usually homogeneous and isointense or slight hyperintense to muscle, whereas on T2-weighted MR images, it is usually more heterogeneous with variable signal intensity. Pathology: Microscopically, the clear cell appearance is due to the accumulation of glycogen. The cells show no or minimal pleomorphism, and paucity of mitotic figures that is in concordance with the slow-growing behavior of the tumor. Scattered multinucleated giant cells are commonly present; areas of necrosis and melanin pigment may be identified. The reciprocal translocation t(12;22)(q13;q12) is observed in more than 90% of clear cell sarcoma cases. In addition, polysomy of chromosome 8 has been observed as a secondary abnormality in many cases of clear cell sarcoma. The differential diagnosis of clear cell sarcoma should include melanoma, epithelioid malignant peripheral nerve sheath tumor, melanotic schwannoma, paraganglioma-like dermal melanocytic tumor, perivascular epithelioid cell neoplasms (PEComas), cellular blue naevus, synovial sarcoma (monophasic type), alveolar soft part sarcoma, paraganglioma, epithelioid sarcoma and carcinomas. Treatment and Prognosis: The treatment of choice for clear cell sarcoma is wide surgical resection. If complete excision is achieved, adjuvant treatments are not unnecessary. Chemotherapy is predominantly employed in patients with metastatic disease. The 5 to 20 year survival of the patients with clear cell sarcoma range from 67% to 10%. The rates of local recurrence ranges up to 84%, late metastases up to 63%, and metastases at presentation up to 30%.

Molecular diagnostics complementing morphology in superficial mesenchymal tumors

Molecular techniques are increasingly important in the practice of surgical pathology. In soft tissue tumors, there are a number of tumors with recurring cytogenetic abnormalities. Knowledge of these abnormalities has furthered our understanding of these tumors and has also allowed development of molecular techniques to aid in the diagnosis. This review will focus on mesenchymal tumors with specific cytogenetic abnormalities that may present as a superficial tumor of the dermis or subcutis.

Cutaneous neoplasms showing EWSR1 rearrangement

Rearrangements of the EWSR1 gene are found in an increasing number of human neoplasms, including several tumors that can involve the skin: Ewing sarcoma/primitive neuroectodermal tumor, angiomatoid (malignant) fibrous histiocytoma, myoepithelioma of soft tissue, and clear cell sarcoma. Although these tumors share this common genetic link, they have very different clinical features, morphology, immunophenotype, and sometimes fusion gene partners; these will be the subjects of this review.

Modeling clear cell sarcomagenesis in the mouse: cell of origin differentiation state impacts tumor characteristics

Clear cell sarcoma (CCS) of tendons and aponeuroses is a deadly soft-tissue malignancy resembling melanoma, with a predilection for young adults. EWS-ATF1, the fusion product of a balanced chromosomal translocation between chromosomes 22 and 12, is considered the definitional feature of the tumor. Conditional expression of the EWS-ATF1 human cDNA in the mouse generates CCS-like tumors with 100% penetrance. Tumors, developed through varied means of initiating expression of the fusion oncogene, model human CCS morphologically, immunohistochemically, and by genome-wide expression profiling. We also demonstrate that although fusion oncogene expression in later stages of differentiation can transform mesenchymal progenitor cells and generate tumors resembling CCS generally, expression in cells retaining stem cell markers permits the full melanoma-related phenotype.

A broad survey of cathepsin K immunoreactivity in human neoplasms

Cathepsin K is consistently and diffusely expressed in alveolar soft part sarcoma (ASPS) and a subset of translocation renal cell carcinomas (RCCs). However, cathepsin K expression in human neoplasms has not been systematically analyzed. We constructed tissue microarrays (TMA) from a wide variety of human neoplasms, and performed cathepsin K immunohistochemistry (IHC). Only 2.7% of 1,140 carcinomas from various sites exhibited cathepsin K labeling, thus suggesting that among carcinomas, cathepsin K labeling is highly specific for translocation RCC. In contrast to carcinomas, cathepsin K labeling was relatively common (54.6%) in the 414 mesenchymal lesions studied, including granular cell tumor, melanoma, and histiocytic lesions, but not paraganglioma, all of which are in the morphologic differential diagnosis of ASPS. Cathepsin K IHC can be helpful in distinguishing ASPS and translocation RCC from some but not all of the lesions in their differential diagnosis.

Molecular detection and targeting of EWSR1 fusion transcripts in soft tissue tumors

Soft tissue tumors are a heterogeneous group of tumors, traditionally classified according to morphology and histogenesis. Molecular classification divides sarcomas into two main categories: (a) sarcomas with specific genetic alterations and (b) sarcomas showing multiple complex karyotypic abnormalities without any specific pattern. Most chromosomal alterations are represented by translocations which are increasingly detected. The identification of fusion transcripts, in fact, not only support the diagnosis but also provides the basis for the development of new therapeutic strategies aimed at blocking aberrant activity of the chimeric proteins. One of the genes most susceptible to breakage/translocation in soft tissue tumors is represented by Ewing sarcoma breakpoint region 1 (EWSR1). This gene has a large number of fusion partners, mainly associated with the pathogenesis of Ewing's sarcoma but with other soft tissue tumors too. In this review, we illustrate the characteristics of this gene/protein, both in normal cellular physiology and in carcinogenesis. We describe the different fusion partners of EWSR1, the molecular pathways in which is involved and the main molecular biology techniques for the identification of fusion transcripts and for their inhibition.

EWS/ATF1 expression induces sarcomas from neural crest-derived cells in mice

Clear cell sarcoma (CCS) is an aggressive soft tissue malignant tumor characterized by a unique t(12;22) translocation that leads to the expression of a chimeric EWS/ATF1 fusion gene. However, little is known about the mechanisms underlying the involvement of EWS/ATF1 in CCS development. In addition, the cellular origins of CCS have not been determined. Here, we generated EWS/ATF1-inducible mice and examined the effects of EWS/ATF1 expression in adult somatic cells. We found that forced expression of EWS/ATF1 resulted in the development of EWS/ATF1-dependent sarcomas in mice. The histology of EWS/ATF1-induced sarcomas resembled that of CCS, and EWS/ATF1-induced tumor cells expressed CCS markers, including S100, SOX10, and MITF. Lineage-tracing experiments indicated that neural crest-derived cells were subject to EWS/ATF1-driven transformation. EWS/ATF1 directly induced Fos in an ERK-independent manner. Treatment of human and EWS/ATF1-induced CCS tumor cells with FOS-targeted siRNA attenuated proliferation. These findings demonstrated that FOS mediates the growth of EWS/ATF1-associated sarcomas and suggest that FOS is a potential therapeutic target in human CCS.

Tumors with EWSR1-CREB1 and EWSR1-ATF1 fusions: the current status

EWSR1-CREB1 and EWSR1-ATF1 are gene fusions of which one or both have now been consistently described in 5 histopathologically and behaviorally diverse neoplasms: angiomatoid fibrous histiocytoma, conventional clear cell sarcoma (of tendons and aponeuroses), clear cell sarcoma-like tumor of the gastrointestinal tract, hyalinizing clear cell carcinoma of the salivary gland, and primary pulmonary myxoid sarcoma. Some of the tumors in this group have been described only recently, and others have been the subject of recent genetic insights contributing to their characterization. These neoplasms are all rare; yet, the increasing frequency with which EWSR1-CREB1 and EWSR1-ATF1 fusions are being described in separate entities is noteworthy. The additional molecular mechanisms by which tumors with such variable morphologic, immunohistochemical, and clinical phenotypes are generated are yet to be understood. We review the clinicopathologic and molecular features of this group of neoplasms unified by the presence of EWSR1-CREB1 and EWSR1-ATF1 genetic fusions.

FUS rearrangements are rare in 'pure' sclerosing epithelioid fibrosarcoma

Several recent reports have described low-grade fibromyxoid sarcoma with sclerosing epithelioid fibrosarcoma-like areas. We evaluated cases of pure sclerosing epithelioid fibrosarcoma lacking areas of low-grade fibromyxoid sarcoma for FUS rearrangement to determine whether this entity could be related to low-grade fibromyxoid sarcoma. Available formalin-fixed paraffin-embedded tissue of 27 sclerosing epithelioid fibrosarcoma from 25 patients was retrieved and tabulated with clinical information. Unstained slides from formalin-fixed paraffin-embedded blocks were prepared and fluorescence in-situ hybridization was performed using a commercial FUS break-apart probe. The median patient age at presentation was 50 (range, 14-78) years, with 14 males and 10 females. Sclerosing epithelioid fibrosarcoma most commonly involved the extremities (n=8) or chest (n=6). Sixteen patients had a median follow-up of 17 (range, 1-99) months; seven were alive and well at 12 (range, 5-30) months; three alive with disease at 28 (range, 9-99) months; five dead of disease at a median of 22 (range, 1-36) months and one was dead of unknown causes. Twelve patients were known to have metastases; the most common site was lung (n=7), followed by bone (n=3), lymph nodes (n=2) and peritoneum (n=1). Only 2 of 22 (9%) analyzable cases of sclerosing epithelioid fibrosarcoma showed rearrangement in the FUS locus by fluorescence in-situ hybridization. Although cytogenetically confirmed low-grade fibromyxoid sarcoma can have sclerosing epithelioid fibrosarcoma-like areas, FUS rearrangement, which is characteristic of low-grade fibromyxoid sarcoma, appears to be relatively rare in pure sclerosing epithelioid fibrosarcoma.

Primary pulmonary myxoid sarcoma with EWSR1-CREB1 fusion: a new tumor entity

We present clinicopathologic data on 10 pulmonary myxoid sarcomas, which are defined by distinctive histomorphologic features and characterized by a recurrent fusion gene, that appear to represent a distinct tumor entity at this site. The patients [7 female, 3 male; aged 27 to 67 y (mean, 45 y)] presented with local or systemic symptoms (n=5), symptoms from cerebral metastasis (1), or incidentally (2). Follow-up of 6 patients showed that 1 with brain metastasis died shortly after primary tumor resection, 1 developed a renal metastasis but is alive and well, and 4 are disease free after 1 to 15 years. All tumors involved pulmonary parenchyma, with a predominant endobronchial component in 8 and ranged from 1.5 to 4 cm. Microscopically, they were lobulated and composed of cords of polygonal, spindle, or stellate cells within myxoid stroma, morphologically reminiscent of extraskeletal myxoid chondrosarcoma. Four cases showed no or minimal atypia, 6 showed focal pleomorphism, and 5 had necrosis. Mitotic indices varied, with most tumors not exceeding 5/10 high-power fields. Tumors were immunoreactive for only vimentin and weakly focal for epithelial membrane antigen. Of 9 tumors, 7 were shown to harbor a specific EWSR1-CREB1 fusion by reverse transcription-polymerase chain reaction and direct sequencing, with 7 of 10 showing EWSR1 rearrangement by fluorescence in situ hybridization. This gene fusion has been described previously in 2 histologically and behaviorally different sarcomas: clear cell sarcoma-like tumors of the gastrointestinal tract and angiomatoid fibrous histiocytomas; however, this is a novel finding in tumors with the morphology we describe and that occur in the pulmonary region.

Clear-cell sarcoma of the soft tissue--a rare diagnosis with a fatal outcome

Clear-cell sarcomas account for less than 1% of all soft tissue tumours. They most often occur in middle-aged adults as a deeply located lesion with predilection to the tendons and aponeuroses. The aim of the present study was to show possible influencing factors on the outcome after surgical treatment in a detailed case series. We reviewed the medical records of 11 patients with the diagnosis of a clear-cell sarcoma of the soft tissue. These cases were analysed with regard to age, gender, localisation, tumour size, recurrence free survival and overall survival. A minimum follow up of 12 months was achieved. The mean age at the point of diagnosis was 47.9 years. Metastases occurred after a mean of 19.2 months. In the cases with a tumour diameter >5 cm, metastases occurred earlier. When treated in a specialist centre, metastases occurred later. Patients died a mean of 18.4 months after developing metastatic disease. Patients with tumour size >5 cm at the point of primary diagnosis died earlier than patients with a tumour size <5 cm. It is important to detect clear-cell sarcomas as soon as possible and the final surgical treatment should be performed in a centre familiar with the treatment of soft tissue tumours not only to prolong overall survival, but also to treat the patient in a multiprofessional team.

Angiomatoid fibrous histiocytoma: unusual sites and unusual morphology

Angiomatoid fibrous histiocytoma is a soft tissue neoplasm of low malignant potential, typically occurring in the superficial soft tissues of the extremities in children and young adults. Occurrence outside somatic soft tissues is most uncommon. This report describes eight such cases, involving the lung (three cases), mediastinum (one case), vulva (two cases), retroperitoneum (one case) and ovary (one case), with the latter three locations being hitherto unreported sites of occurrence. Patients had a median age of 48 years, and presented with symptoms related to the mass lesion (five cases) or were incidentally found to harbor a tumor (three cases). Besides the typical histological features such as an outer shell of lymphoid tissue, multinodular aggregates of dendritic-like tumor cells, blood-filled spaces and abundant admixed plasma cells, unusual features were found focally in some cases, including clear cells, rhabdomyoblast-like cells, pulmonary edema-like pattern and tumor cell cords lying in a myxoid stroma. Immunoreactivity for the epithelial membrane antigen, desmin, smooth-muscle actin, CD68 and CD99 was found in 100, 63, 43, 100 and 100% of cases, respectively. Molecular studies provided support for the diagnosis in all seven tested cases-EWS gene translocation in six cases (partner gene being CREB1 in three and ATF1 in two in which information was available) and FUS gene translocation in one case. Comparison of the reported cases of extrasomatic angiomatoid fibrous histiocytoma with their somatic soft tissue counterparts showed a number of differences: higher mean age, slight male predominance (particularly for bone lesions), larger tumors, higher frequency of systemic symptoms, higher recurrence rate, myxoid change being more common and a much higher frequency of EWS/ATF1 gene fusion.

Clear Cell Tumors of Soft Tissue

Clear cell lesions of soft tissue include varying morphologic patterns and a range of clinical behaviors and prognoses. Benign lesions include perivascular epithelioid cell tumors, clear cell fibrous papule, and distinctive dermal clear cell mesenchymal tumor; malignant tumors include clear cell sarcoma, liposarcoma, and rare malignant perivascular epithelioid cell tumors. Clear cell variants of other benign and malignant soft tissue tumors include fibrous histiocytoma, atypical fibroxanthoma, myoepithelioma, leiomyoma and leiomyosarcoma, and rhabdomyosarcoma. Metastatic clear cell tumors, including renal cell carcinoma and adrenal cortical carcinoma, should be considered in the differential diagnosis and excluded through clinical history, imaging studies, and immunohistochemical stains.

EWSR1-ATF1 fusion is a novel and consistent finding in hyalinizing clear-cell carcinoma of salivary gland

Hyalinizing clear-cell carcinoma (HCCC) is a rare, low-grade salivary gland tumor with distinctive clear-cell morphology and pattern of hyalinization as well as focal mucinous differentiation. However, histological overlap exists with other salivary gland tumors, such as epithelial-myoepithelial carcinoma (EMCa), salivary myoepithelial carcinoma, and mucoepidermoid carcinoma (MEC). The potential relationship between HCCC and its morphological mimics has not been yet investigated at the genetic level. In this study, we conducted a molecular analysis for the presence of rearrangements in MAML2, commonly seen in MECs, and EWSR1, involved in "soft tissue myoepithelial tumors" (SMET) by fusion with POU5F1, PBX1, or ZNF444. Fluorescence in situ hybridization (FISH) was performed on 23 HCCC cases for abnormalities in MAML2, EWSR1, FUS, POU5F1, PBX1, and ZNF444. FISH for MAML2 was negative in all cases (0 of 14), including those with mucinous differentiation (0 of 7). An EWSR1 rearrangement was identified in 18 of 22 HCCCs (82%), while no break-apart signals were seen in FUS, POU5F1, PBX1, or ZNF444. 3'RACE on an EWSR1 rearranged HCCC identified an EWSR1-ATF1 fusion, which was confirmed by RT-PCR. ATF1 involvement was further confirmed by FISH analysis in 13 of 14 EWSR1-rearranged HCCC cases (93%). In contrast, all control cases tested, including among others 5 EMCa and 3 MEC with clear cells, were negative for EWSR1 and ATF1 rearrangements. The presence of EWSR1-ATF1 fusion in most HCCCs reliably separates these tumors from its histological mimics. The distinction from MEC is particularly important, as conventional MEC grading schemes overgrade these indolent HCCCs, potentially impacting on treatment.

Diagnostic utility of EWS break-apart fluorescence in situ hybridization in distinguishing between non-cutaneous melanoma and clear cell sarcoma

Clear cell sarcoma (CCS) is a rare soft tissue sarcoma with morphological similarities to malignant melanoma (MM), but with a distinct genetic background that includes the chromosomal translocation t(12;22)(q13;q12). Clear cell sarcoma is often misdiagnosed as MM because of similarities in target locations and immunophenotypes. Eighteen cases with MM in non-cutaneous sites were subjected to fluorescence in situ hybridization (FISH) to assess EWS gene breakage. Tissue microarrays were constructed using formalin-fixed, paraffin-embedded tissue and the EWSR1 (22q12) dual-color, break-apart rearrangement probe (Vysis) was used. Two patients were classified as CCS with EWS gene rearrangement, with a mean of 67.5% positive cells per sample according to break-apart FISH. The remaining 16 patients lacked break-apart signals of the EWS gene. The presence of type 1 (EWS exon 8-ATF1 exon 4) fusion transcripts was confirmed in FISH-positive patients by RT-PCR. Retrospective analysis revealed that the masses were located in the foot and buttock, respectively. Morphologically, tumor cells were not typical for those of CCS or MM. Break-apart FISH is an accurate and convenient method for differentiating between MM and CCS. Molecular detection of EWS gene rearrangement, either by break-apart FISH or RT-PCR, is mandatory in subjects with melanotic tumors of soft tissue.

Clear cell sarcoma of tendons and aponeuroses, and osteoclast-rich tumour of the gastrointestinal tract with features resembling clear cell sarcoma of soft parts: a review and update

Clear cell sarcoma (CCS) is a rare, distinctive soft tissue neoplasm, typically occurring in the distal extremities of young adult patients. Although CCS shows melanocytic differentiation, it is now clear that it is clinicopathologically and genetically distinct from conventional malignant melanoma. The 'osteoclast-rich tumour of the gastrointestinal tract with features resembling clear cell sarcoma of soft parts' is an extraordinarily rare gastrointestinal neoplasm that shares some features of CCS, but differs from it in other ways. The historical, histopathological, ultrastructural, immunohistochemical and genetic aspects of these two tumours are reviewed in this article.

Small blue round cell tumor of the interosseous membrane bearing a t(2;22)(q34;q12)/EWS-CREB1 translocation: a case report

Background

The group of small blue round cell tumors encompasses a heterogeneous group of neoplasms characterized by primitive appearing round cells with few distinguishing histologic features.

Results

We report the case of a small blue round cell tumor with an EWS gene rearrangement detected by fluorescent in situ hybridization (FISH) analysis that mimicked Ewing sarcoma, but with unusual histology and immunohistochemical features. Multi-color karyotyping identified the presence of a t(2;22)(q34;q12) that was initially expected to represent a variant EWSR1-FEV translocation. After an extensive workup, the lesion is considered to represent a clear cell sarcoma harboring an EWSR1-CREB1 fusion transcript.

Conclusions

This case appears to represent a rare variant of clear cell sarcoma arising in peripheral soft tissues with unusual histology and unique immunophenotype. In this circumstance, FISH for all EWSR1 translocation partners or RT- PCR for a spectrum of possible transcript variants is critically important for diagnosis, since cytogenetic analysis or clinical FISH assay using only commercial EWSR1 probes will be misleading.

The clinical relevance of molecular genetics in soft tissue sarcomas

Bone and soft tissue sarcomas are an infrequent and heterogeneous group of mesenchymal tumors including more than a hundred different entities attending to histologic patterns. Research into the molecular aspects of sarcomas has increased greatly in the last few years. This enormous amount of knowledge has allowed, for instance, to refine the classification of sarcomas, improve the diagnosis, and increase the number of therapeutical targets available, most of them under preclinical evaluation. However, other important key issues, such as sarcomagenesis and the cell of origin of sarcomas, remain unresolved. From a molecular point of view, these neoplasias are grouped into 2 main types: (a) sarcomas showing relatively simple karyotypes and translocations, which originate gene fusions (eg, EWS-FLI1 in Ewing sarcoma) or point mutations (eg, c-kit in the gastrointestinal tumors) and (b) sarcomas showing unspecific gene alterations, very complex karyotypes, and no translocations. The discovery of the early mechanisms involved in the genesis of sarcomas, the more relevant signaling pathways, and the development of genetically engineered mouse models could also provide a new individualized therapeutic strategy against these tumors. This review describes the clinical application of some of the molecular alterations found in sarcomas, some advances in the field of sarcomagenesis, and the development of animal models.

Soft tissue tumors associated with EWSR1 translocation

The Ewing sarcoma breakpoint region 1 (EWSR1; also known as EWS) represents one of the most commonly involved genes in sarcoma translocations. In fact, it is involved in a broad variety of mesenchymal lesions which includes Ewing's sarcoma/peripheral neuroectodermal tumor, desmoplastic small round cell tumor,clear cell sarcoma, angiomatoid fibrous histiocytoma, extraskeletal myxoid chondrosarcoma, and a subset of myxoid liposarcoma. The fusion products between EWSR1 and partners usually results in fusion of the N-terminal transcription-activating domain of EWSR1 and the C-terminal DNA-binding domain of the fusion partner, eventually generating novel transcription factors. EWSR1 rearrangement can be visualized by the means of fluorescence in situ hybridization (FISH). As soft tissue sarcomas represent a diagnostically challenging group, FISH analysis is an extremely useful confirmatory diagnostic tool. However, as in most instances a split-apart approach is used, the results of molecular genetics must be evaluated in context with morphology.

The impact of advances in molecular genetic pathology on the classification, diagnosis and treatment of selected soft tissue tumors of the head and neck

Recent advances in molecular pathology have had a significant impact on the diagnosis, classification, and treatment of soft tissue tumors. The practical application of these discoveries promises to assist greatly in the evaluation and treatment of soft tissue neoplasms in the head and neck region-an area characterized by exceedingly complex anatomy that often restricts the ample sampling of lesions and complete surgical resection. This reviews details some ways in which molecular techniques have strengthened conventional diagnostic and management approaches to low-grade fibromyxoid sarcoma, angiomatoid (malignant) fibrous histiocytoma, and dermatofibrosarcoma protuberans, all of which may involve the head and neck region.

Detection and characterization of EWSR1/ATF1 and EWSR1/CREB1 chimeric transcripts in clear cell sarcoma (melanoma of soft parts)

Unlike melanoma, clear cell sarcoma harbors either a t(12;22)(q13;q12) recurrent translocation, resulting in an EWSR1/ATF1 chimeric gene, or less commonly a t(2;22)(q34;q12) translocation fusing EWSR1 and CREB1. Few studies have examined the prevalence of all chimeric types and variants to assess the usage of ancillary genetic testing in routine diagnosis. We investigated rearrangement prevalence in 17 clear cell sarcomas, two positive control cell lines, and two melanomas (negative controls). Fluorescence in situ hybridization (FISH) analysis using the LSI EWSR1 break-apart probe and a reverse transcription polymerase chain reaction (RT-PCR) assay optimized for formalin-fixed paraffin-embedded tissue to detect all four reported EWSR1/ATF1 clear cell sarcoma chimeric types and the EWSR1/CREB1 variant was performed. All 15 cases available for testing by FISH were positive for EWSR1 rearrangement including two cases with insufficient RNA for RT-PCR. Thirteen of 15 cases successfully tested by RT-PCR harbored a type 1 chimeric transcript (EWSR1 exon 8/ATF1 exon 4), of which five tumors simultaneously carried a type 2 chimeric transcript (EWSR1 exon 7/ATF1 exon 5). One case carried a type 2 transcript alone and one case contained an EWSR1/CREB1 transcript. Both control cases were positive by both techniques with one case carrying both types 1 and 2 chimeric transcripts and the other types 2 and 3 (EWSR1 exon 10/ATF1 exon 5). Consequently, both techniques are equally effective in assessing for an EWSR1 rearrangement and are useful ancillary diagnostic tests for clear cell sarcoma. They also reinforce the prevalence of this translocation in these tumors. In addition, EWSR1-CREB1 was identified in a clear cell sarcoma of soft tissue providing further evidence that this chimeric variant is not exclusive to gastrointestinal clear cell sarcomas and should be included in RT-PCR assays of soft tissue clear cell sarcomas.

Classification and pathology

Soft tissue tumors are a heterogeneous group of benign and malignant processes. Some are assumed to be reactive; others are clearly neoplastic. Because of their rarity, they frequently pose diagnostic problems for surgical pathologists. Accurate diagnosis of these tumors is enhanced by knowledge of the clinical features of the given lesions and, at times, by application of immunohistochemical and molecular techniques. In this article the lesions are described essentially in accordance with the World Health Organization classification.

Gastrointestinal melanoma or clear cell sarcoma? Molecular evaluation of 7 cases previously diagnosed as malignant melanoma

Clear cell sarcoma (CCS) is a rare tumor classically associated with the tendons and aponeuroses of distal extremities of young adults. CCS and malignant melanoma (MM) share immunohistochemical profiles and ultrastructural features, but classic CCS has characteristic morphology with low mitotic activity and minimal pleomorphism. Occasional cases show pleomorphism, high mitotic index, and/or melanin pigmentation, making CCS indistinguishable from MM based on morphology. However, CCS is genetically distinct owing to its consistent association with a t(12;22)(q13;q12) chromosomal translocation, leading to the formation of the EWS/ATF1 fusion transcript. This translocation has never been documented in cutaneous melanoma, and thus is regarded as specific for CCS. Recent evidence suggests that primary "malignant melanomas" in unusual anatomic sites, most notably the gastrointestinal (GI) tract, may be CCS. This is supported by 11 cases of primary GI CCS with the t(12;22) translocation. We used reverse-transcription polymerase chain reaction and fluorescence in situ hybridization to examine whether a proportion of cases diagnosed as MM of the GI tract in patients without a history of cutaneous MM actually represent primary GI CCS. In total, we examined 7 cases: Four with no prior history of MM, 2 with histories of cutaneous MM, and 1 with an anal MM. All 4 cases for which there was no history of cutaneous/mucosal MM harbored the EWS/ATF1 fusion transcript. We report the largest series of GI CCS and have shown that molecular studies may be warranted in cases that otherwise seem to represent MM of unusual primary locations.

Intestinal clear cell sarcoma with melanocytic differentiation and EWS [corrected] rearrangement: report of a case

A clear cell sarcoma-like tumor with osteoclast-like giant cells of the gastrointestinal tract without immunoexpression of CD117 was recently proposed as a new tumor entity. In this article, a case of a 37-year-old man with a neoplasm of the jejunum composed of polygonal cells with clear to eosinophilic cytoplasm forming nests and fascicles is reported. Giant cells were not identified. Immunohistochemically, the tumor cells expressed strongly S100 protein, human melanoma black 45, platelet-derived growth factor receptor alpha, B-cell lymphoma 2, p53, and to a lesser extent vimentin, neuron-specific enolase, and epithelial membrane antigen. Mindbomb homolog-1 index was 35%. Immunoreactivity for CD34 and CD117 was negative. The fluorescence in situ hybridization analysis showed a translocation involving chromosome 22q12, the diagnostic hallmark of clear cell sarcoma of soft tissues. This case indicates a close histogenetic relationship with the recently reported clear cell sarcoma with osteoclast-like giant cells of the gastrointestinal tract, as well as with the clear cell sarcoma of soft tissues.

Clear cell sarcoma of soft tissue: a clinicopathologic, immunohistochemical, and molecular analysis of 33 cases

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.

PEComa: another member of the MiT tumor family?

We report 2 cases of PEComa, one occurring in the colon of an 11-year-old boy and the other in the bone (fibula) of a 92-year-old woman. Both tumors consisted of nests of large epithelioid cells surrounded by a fibrovascular stroma. The nuclei were large and vesicular, with prominent centrally located nucleoli. The cytoplasm was eosinophilic, with a fine to coarse granularity. Mitoses and individual cell necrosis were infrequent. Immunohistochemically, both tumors showed strong cytoplasmic expression of HMB-45 and intense nuclear positivity for TFE3. To our knowledge, nuclear positivity for TFE3 has been previously reported in only 5 cases of PEComa. Reactivity to this marker suggests that PEComa should be added to the growing list of human tumors of the so-called MiT family gene.