Malignant melanoma is genetically distinct from clear cell sarcoma of tendons and aponeurosis (malignant melanoma of soft parts)

Primary clear cell sarcoma of the sacrum: a case report

Clear cell sarcoma, first described by Enzinger in 1965, is an uncommon malignant soft tissue neoplasm that displays melanocytic differentiation. It occurs predominantly in the soft tissue of the extremities in young adults or children. Primary clear cell sarcoma of the bone is extremely rare, only seven cases have been reported to our knowledge. We present here a case of a huge primary clear cell sarcoma of the sacrum arising in a 25-year-old man. The average percentage of melanin content in the tumor was 9.25 ± 6.71%, which resulted in hypointense signal in T2-weighted and heterogeneous hyperintense signal in T1-wieghted images of magnetic resonance imaging (MRI). The patient was treated with curettage of the mass and neither further radiotherapy nor chemotherapy had been provided. The patient had local regrowth of tumor at 9 months after surgery. To our knowledge, this is the first case of CCS in the axial skeleton documented in English literature.

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.

Molecular cytogenetics of cutaneous melanocytic lesions - diagnostic, prognostic and therapeutic aspects

This review intends to update current knowledge regarding molecular cytogenetics in melanocytic tumours with a focus on cutaneous melanocytic lesions. Advantages and limitations of diverse, already established methods, such as (fluorescence) in situ hybridization and mutation analysis, to detect these cytogenetic alterations in melanocytic tumours are described. In addition, the potential value of more novel techniques such as multiplex ligation-dependent probe amplification is pointed out. This review demonstrates that at present cytogenetics has mainly increased our understanding of the pathogenesis of melanocytic tumours, with an important role for activation of the mitogen-activated protein kinase (MAPK) signalling pathway in the initiation of melanocytic tumours. Mutations in BRAF (in common naevocellular naevi), NRAS (congenital naevi), HRAS (Spitz naevi) and GNAQ (blue naevi) can all cause MAPK activation. All these mutations seem early events in the development of melanocytic tumours, but by themselves are insufficient to cause progression towards melanoma. Additional molecular alterations are implicated in progression towards melanoma, with different genetic alterations in melanomas at different sites and with varying levels of sun exposure. This genetic heterogeneity in distinct types of naevi and melanomas can be used for the development of molecular tests for diagnostic purposes. However, at the moment only few molecular tests have become of diagnostic value and are performed in daily routine practice. This is caused by lack of large prospective studies on the diagnostic value of molecular tests including follow-up, and by the low prevalence of certain molecular alterations. For the future we foresee an increasing role for cytogenetics in the treatment of melanoma patients with the increasing availability of targeted therapy. Potential targets for metastatic melanoma include genes involved in the MAPK pathway, such as BRAF and RAS. More recently, KIT has emerged as a potential target in melanoma patients. These targeted treatments all need careful evaluation, but might be a promising adjunct for treatment of metastatic melanoma patients, in which other therapies have not brought important survival advantages yet.

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.

Cutaneous clear cell sarcoma: a clinicopathologic, immunohistochemical, and molecular analysis of 12 cases emphasizing its distinction from dermal melanoma

Clear cell sarcoma (CCS) of tendons and aponeuroses/malignant melanoma (MM) of soft parts is a rare tumor and in the majority of cases presents a characteristic reciprocal translocation t(12;22)(q13;q12) that results in fusion of the EWS and ATF1 genes. Although the melanocytic differentiation of CCS is indisputable, its precise lineage remains unclear. Typically, the slowly growing tumor affects the extremities of adolescents or young adults, especially around the ankle and foot. CCS is classically regarded as a deep soft tissue tumor associated with tendons or aponeuroses. This traditional view is put into perspective by the description of primary CCS of the gastrointestinal tract that may have a variant fusion gene EWSR1-CREB1. We describe 12 cases of cutaneous CCS and discuss the differential diagnoses. These 12 cases share an identical immunohistochemical profile with MM and thus can easily be confused with a dermal variant of spindle cell MM or metastasis of MM. The patients' ages ranged from 6 to 74 years (median: 25 y), and there was a female predominance (10 females, 2 males). Most tumors (n = 9) were located on the extremities, 2 tumors arose on the back, and 1 on the abdomen. The mean tumor size was 0.97 cm (range, 0.4 to 1.7 cm). Six cases showed invasion of the subcutis, the other 6 cases were entirely dermal. Tumor necrosis was evident in 2 cases, melanin pigment in 2 cases, and ulceration in 1 tumor. All cases showed uniform nests and fascicles of pale spindled or slightly epitheloid cells with finely granular eosinophilic or clear cytoplasm. There was fair pleomorphism with plump spindled nuclei and significantly prominent nucleoli. Multinucleated wreath-like tumor giant cells were observed in two-thirds of cases, but were usually present only focally. The dense cellular aggregates were encased by delicate fibrous septa. The stroma showed a sclerotic reticulated pattern. Partly, the nests of spindle cells bordered the epidermis, prima vista mimicking junctional nests of melanocytes. The specific translocation pattern was confirmed in all cases by fluorescence in situ hybridization. Local recurrences and metastases developed in 2 and 3 patients, respectively, and 1 patient died of the disease.

Primary giant clear cell sarcoma (soft tissue malignant melanoma) of the sternum

One case of a primary clear cell sarcoma of the sternum (also called soft tissue melanoma) is reported. This neoplasm represents a rare occurrence, and as a rule, differential diagnosis with melanoma often requires detailed immunohistochemistry and cytogenetic analysis (ie, rearrangement of EWS gene localized on 22q12 chromosome). Because wide resection is recommended, chest wall reconstruction may pose challenging technical issues. In our patient, we elected not to proceed to clavicular stabilization. Nevertheless, acceptable shoulder girdle mobility was observed after surgery.

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.

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.

Molecular mechanisms underlying the MiT translocation subgroup of renal cell carcinomas

Renal cell carcinomas (RCCs) represent a heterogeneous group of neoplasms, which differ in histological, pathologic and clinical characteristics. The tumors originate from different locations within the nephron and are accompanied by different recurrent (cyto)genetic anomalies. Recently, a novel subgroup of RCCs has been defined, i.e., the MiT translocation subgroup of RCCs. These tumors originate from the proximal tubule of the nephron, exhibit pleomorphic histological features including clear cell morphologies and papillary structures, and are found predominantly in children and young adults. In addition, these tumors are characterized by the occurrence of recurrent chromosomal translocations, which result in disruption and fusion of either the TFE3 or TFEB genes, both members of the MiT family of basic helix-loop-helix/leucine-zipper transcription factor genes. Hence the name MiT translocation subgroup of RCCs. In this review several features of this RCC subgroup will be discussed, including the molecular mechanisms that may underlie their development.

Clear cell sarcoma (melanoma of soft parts): The Royal Marsden Hospital experience

INTRODUCTION

Clear cell sarcoma (CCS) is a rare tumour with a propensity for local recurrence and nodal metastasis. About 300 cases have been reported, thus further clarification regarding the course and outcome of the disease is required.

METHODS

Patients with a histopathologic diagnosis of CCS were identified from prospective histopathology and sarcoma databases and supplemented with a retrospective analysis of the patients' hospital records.

RESULTS

Between 1990 and 2005, a total of 72 patients with a diagnosis of CCS were identified, 35 having been referred for management and 37 having been referred for histopathologic opinion. The median age was 39 years (range 5-90 years). Of the 35 patients referred to the Royal Marsden Hospital for management, 23% developed local recurrence or in-transit metastases at a median of 9 months (2-79 months) after resection of the primary, and nodal or distant metastatic disease was seen in 63% after 14 months (range 0-177 months). Five- and 10-year survival were 52% and 25%, respectively.

CONCLUSIONS

CCS has a number of similarities with melanoma, particularly in its peripheral distribution and propensity for nodal disease. Wide excision with clear margins offers the best chance of cure. Local recurrence and regional metastases are common, and are almost always followed by distant metastases and death.

Clear cell sarcoma of the soft parts arising in the rectus abdominis in a child - aspiration cytology of a rare case

BACKGROUND

Clear cell sarcoma of soft parts is most commonly found associated with the tendons and aponeuroses of distal extremities in young adults with a peak incidence in the third decade. Location in the abdominal wall and in a child is very rare.

CASE PRESENTATION

A nine-year-old female child presented with a swelling in the anterior abdominal wall in the suprapubic region. Fine needle aspiration revealed predominantly discrete cells with loose clustering at places. The cytoplasm was abundant, finely granular, and eosinophilic with some cells exhibiting clear vacuolated zones. No pigment was seen. The nuclei were rounded and eccentrically placed with a striking single eosinophilic macro nucleolus present in all the cells. Taking into consideration, the history, age of the patient, location of the tumor and absence of melanin pigment, a diagnosis of soft tissue sarcoma was made, the differential including Clear cell sarcoma. This was subsequently confirmed on histopathological examination and immunohistochemistry

CONCLUSION

The atypical presentation of the case made the cytological diagnosis rather challenging. Clear cell sarcoma should be considered when cytology of a soft-tissue tumor shows uncharacteristically high cellularity and relatively uniform cells with macronucleoli.

Clear cell sarcoma of tendons and aponeuroses: a study of 75 patients

BACKGROUND

Clear cell sarcoma (CCS) of tendons and aponeuroses (malignant melanoma of soft parts) is a rare melanocytic soft tissue sarcoma. The objective of this study was to determine the clinical features, prognostic factors, and optimal treatment policy for patients with this rare disease.

METHODS

Seventy-five consecutive patients with histologically confirmed CCS who received treatment between 1980 and 2004 were analyzed retrospectively.

RESULTS

There were 41 men and 34 women, and the median age was 36 years. Sixty-five tumors were located in the extremities, and 10 tumors were located in the trunk. The median tumor size was 4 cm. Seventy-one patients underwent surgical excision, and 56 patients received chemotherapy. Sixteen patients developed local recurrences, and 52 patients developed metastasis. The overall patient survival rates was 47% at 5 years and 36% at 10 years. Univariate analysis showed that sex (P = .018), tumor size (P = .001), tumor depth (P = .002), TNM classification (P = .001), and surgical margin (P = .042) were significant prognostic factors. Among the 52 patients who presented with localized disease, sex (P = .023), tumor size (P = .002), tumor depth (P = .011), TNM classification (P = .004), and chemotherapy (P = .032) were identified as significant prognostic factors. Multivariate analysis showed that tumor size remained an independent prognostic factor in both groups.

CONCLUSIONS

The current results supported the contention that early diagnosis and initial wide excision are essential for a favorable outcome of CCS. The role of chemotherapy for CCS should be investigated further.

Clear Cell Sarcoma of Tendons and Aponeuroses: A Review

Clear cell sarcoma of tendons and aponeuroses, also referred to as malignant melanoma of soft parts, is a rare malignancy derived from neural crest cells. It usually presents in the distal lower extremities of young adults, frequently attached to tendons or aponeuroses. It behaves like a high-grade soft tissue sarcoma and is associated with poor overall survival. Magnetic resonance imaging studies of the lesion reveal T1 hypointensity, T2 hyperintensity, and gadolinium uptake. Grossly, the tumor is usually circumscribed with a histologic pattern of uniform polygonal to fusiform cells with clear to pale eosinophilic cytoplasm divided into variably sized clusters by fibrous septa. Immunohistochemical studies in most cases show that the neoplastic cells are positive with HMB-45 and react with antibody against S100 protein. Most cases show a reciprocal cytogenetic translocation t(12;22)(q13;q12) that creates a unique chimeric fusion EWSR1/ATF1 gene transcript. Metastasis occurs mainly to regional lymph nodes and lungs. Poor prognostic indicators include a tumor size equal to or more than 5 cm, presence of metastasis, and necrosis. The mainstay of treatment is wide excision of the tumor. The use of sentinel lymph node biopsy may become an important procedure in detecting occult regional metastasis and guiding the extent of surgery. The beneficial effects of adjuvant chemotherapy and radiotherapy have not been fully evaluated. This article provides a short overview of the current knowledge of clear cell sarcoma of tendons and aponeuroses.

EWS-CREB1: a recurrent variant fusion in clear cell sarcoma--association with gastrointestinal location and absence of melanocytic differentiation

PURPOSE

Clear cell sarcoma (CCS) usually arises in the lower extremities of young adults and is typically associated with a t(12;22) translocation resulting in the fusion of EWS (EWSR1) with ATF1, a gene encoding a member of the cyclic AMP-responsive element binding protein (CREB) family of transcription factors. CCS arising in the gastrointestinal tract is rare and its pathologic and molecular features are not well defined.

EXPERIMENTAL DESIGN

We report a novel variant fusion of EWS to CREB1, a gene at 2q32 encoding another CREB family member highly related to ATF1, detected in three women with gastrointestinal CCS. All three cases contained an identical EWS-CREB1 fusion transcript that was shown by reverse transcription-PCR. In two of the cases tested, EWS gene rearrangement was also confirmed by fluorescence in situ hybridization and the EWS-CREB1 genomic junction fragments were isolated by long-range DNA PCR.

RESULTS

Morphologically, all three tumors lacked melanin pigmentation. By immunohistochemistry, there was a strong and diffuse S100 protein reactivity, whereas all melanocytic markers were negative. Ultrastructurally, two of the cases lacked melanosomes. The melanocyte-specific transcript of MITF was absent in two cases, and only weakly expressed in the third case. The Affymetrix gene expression data available in one case showed lower expression of the melanocytic genes MITF, TYR, and TYRP1, compared with four EWS-ATF1-positive CCSs of non-gastrointestinal origin.

CONCLUSIONS

EWS-CREB1 may define a novel subset of CCS that occurs preferentially in the gastrointestinal tract and shows little or no melanocytic differentiation. Thus, evidence of melanocytic lineage or differentiation is not a necessary feature of sarcomas with gene fusions involving CREB family members.

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.

Oncogenic MITF dysregulation in clear cell sarcoma: defining the MiT family of human cancers

Clear cell sarcoma (CCS) harbors a pathognomonic chromosomal translocation fusing the Ewing's sarcoma gene (EWS) to the CREB family transcription factor ATF1 and exhibits melanocytic features. We show that EWS-ATF1 occupies the MITF promoter, mimicking melanocyte-stimulating hormone (MSH) signaling to induce expression of MITF, the melanocytic master transcription factor and an amplified oncogene in melanoma. Knockdown/rescue studies revealed that MITF mediates the requirement of EWS-ATF1 for CCS survival in vitro and in vivo as well as for melanocytic differentiation. Moreover, MITF and TFE3 reciprocally rescue one another in lines derived from CCS or pediatric renal carcinoma. Seemingly unrelated tumors thus employ distinct strategies to oncogenically dysregulate the MiT family, collectively broadening the definition of MiT-associated human cancers.

Utility of CD117 Immunoreactivity in Differentiating Metastatic Melanoma From Clear Cell Sarcoma

Context.—Clear cell sarcoma is a malignant soft tissue tumor with melanocytic differentiation. Molecular methods are sometimes necessary to identify the unique t(12; 22)(q13;q12) translocation and differentiate clear cell sarcoma from melanoma.

Objective.—To determine whether CD117 immunoreactivity may be useful in separating melanoma from clear cell sarcoma.

Design.—We identified 20 tumors listed in our surgical pathology files that were diagnosed as clear cell sarcoma or in which clear cell sarcoma was strongly considered. These were tested for the presence of the t(12;22) translocation by reverse transcriptase/polymerase chain reaction and sequencing from paraffin-embedded tissue. Tumors with a t(12;22) translocation were immunostained with an antibody to CD117 and compared with 16 similarly stained metastatic melanomas.

Results.—Twelve tumors from 9 patients demonstrated t(12;22). No metastatic melanomas demonstrated t(12;22). None of the 12 clear cell sarcomas showed membrane or cytoplasmic staining for CD117. Conversely, 10 (63%) of 16 metastatic melanomas were, at least focally, positive for CD117; this difference was significant (P < .001). Interestingly, 3 tumors in which clear cell sarcoma was initially considered as a diagnosis, but which lacked t(12;22), were also positive for CD117.

Conclusions.—Reverse transcriptase/polymerase chain reaction, performed on paraffin-embedded tissue, is a useful, rapid tool for identifying the presence of t(12;22) in clear cell sarcoma. The CD117 immunoreactivity may prove useful in the differential diagnosis of deep soft tissue or visceral lesions with melanocytic differentiation; positive staining results exclude clear cell sarcoma, but are compatible with metastatic melanoma.

Diagnosis of clear cell sarcoma by real-time reverse transcriptase-polymerase chain reaction analysis of paraffin embedded tissues

BACKGROUND

Clear cell sarcoma (CCS) is a rare tumor with a very poor prognosis that occurs predominantly in the distal extremities of young adults. Most patients bear the t(12;22) reciprocal translocation, which involves the EWS and ATF1 genes. The diagnosis of CCS usually is easy but may be challenging in unusual sites, and the detection of EWS-ATF1 fusion transcripts is helpful to rule out a metastatic melanoma.

METHODS

Forty-four patients with CCS and 14 conventional melanomas were examined for the presence of EWS-ATF1 transcripts by using real-time polymerase chain reaction (PCR) analysis on paraffin embedded tissues, including frozen samples for 9 CCS samples and 9 melanoma samples. Prior to molecular analysis, the diagnosis of CCS was considered certain in 35 patients and as probable in 9 patients on the basis of location, histologic features, and immunohistochemical profile. Treatment modalities and follow-up were available for 41 patients with CCS.

RESULTS

EWS-ATF1 fusion transcripts were detected in 38 paraffin embedded CCS tissues (86% of all samples; 93% of interpretable samples), 3 samples (7%) were negative, and 3 samples (7%) were considered uninterpretable. Fusion transcripts were detected in 7 of 9 samples for which the diagnosis of CCS was considered probable. EWS-ATF1 transcripts were not detected in the 14 samples of melanoma. Results from frozen tissues were concordant with those from all corresponding paraffin embedded samples. Twenty-eight of 41 patients (68%) experienced lymph node and/or distant metastasis, and the 5 year-survival rate was 44%. Mitotic index and histologic grade were predictive of survival and distant metastasis.

CONCLUSIONS

The results of this study showed that the molecular detection of EWS-ATF1 fusion transcript by real-time PCR on paraffin embedded tissues is a sensitive and specific method for the diagnosis of CCS. It is an efficient tool for the diagnosis of unusual tumors, especially with regard to its distinction from melanoma. The current results also confirmed the poor prognosis for patients with this tumor type. Mitotic index and grade were predictive factors for survival and distant metastasis.

[Clear-cell sarcoma of tendons and aponeuroses: three case reports]

Clear-cell sarcoma (CCS) of tendons and aponeuroses is a rare malignant tumor representing about 1% of soft tissue tumors. Preferentially observed in young adults in the second or third decade, the tumor generally develops in the limbs. Only 2% of SCC of tendons and aponeuroses have been reported in children less than 10 years of age. This slowly progressive tumor usually forms a painless mass. The tumor increases in size followed by metastatic dissemination to lymph nodes and the lungs. The prognosis is related to tumor size. At the present time, the recognized limit is greater than 5 cm. Early diagnosis must be achieved to enable effective treatment by carcinological surgical resection. We report the three cases of CCS of tendons and aponeuroses observed at the Strasbourg University hospital over a 35-year period. Each case had a special clinical presentation. The first patient, treated in 1967, presented tumor bone lysis on the plain x-ray, an observation rarely reported in the literature. In the second patient, treated in 2002, the tumor was discovered after trauma. This patient developed skin ulceration associated with paraplegia secondary to metastatic thoracic cord compression. The third case occurred in a 12-year-old girl, treated in 2002.

Dual-color, break-apart fluorescence in situ hybridization for EWS gene rearrangement distinguishes clear cell sarcoma of soft tissue from malignant melanoma

Clear cell sarcoma of soft tissue (malignant melanoma of soft parts) is a soft tissue sarcoma with melanocytic differentiation that typically occurs in the tendons and aponeuroses of young adults. As demonstrated by cytogenetics and reverse-transcriptase polymerase chain reaction, between 70% and over 90% of clear cell sarcomas have a t(12;22) translocation, fusing the EWS and ATF1 genes on chromosomes 22q12 and 12q13, respectively. Identification of this translocation distinguishes clear cell sarcoma from histologic mimics, most importantly conventional malignant melanoma. We report our experience with a commercially available, dual-color, break-apart fluorescence in situ hybridization (FISH) probe, which allows detection of EWS (22q12) gene rearrangement in formalin-fixed, paraffin-embedded tissues. Histologically and immunophenotypically well-characterized cases of clear cell sarcoma (n = 10) and malignant melanoma (n = 32) were evaluated with a 22q12 dual-color, break-apart probe (Vysis, Downer's Grove, IL, USA), which spans the known common breakpoints in the EWS gene on chromosome 22 (introns 7-10). Signals from tumor cell nuclei were counted under a fluorescence microscope and the presence of red-green break-apart signals was recorded. Of the clear cell sarcoma cases, seven of 10 showed evidence of an EWS gene rearrangement with a mean of 81.6% positive cells per sample (range: 60-95%). All cases of malignant melanoma (n = 32) showed virtually absent break-apart signals in the EWS gene (less than 4% cells per case). FISH detects EWS gene rearrangement in a substantial proportion of clear cell sarcomas, with excellent specificity. Importantly, EWS FISH is negative in malignant melanoma, a clinically dissimilar tumor, which may closely mimic clear cell sarcoma histologically and immunohistochemically. As the studied probe can be utilized in routinely processed tissue, FISH provides an excellent alternative to reverse-transcriptase polymerase chain reaction in cases where fresh tissue is unavailable.

Unusual histological variants of cutaneous malignant melanoma with some clinical and possible prognostic correlations

Malignant melanoma is known for the wide range of histological patterns it can assume mimicking other malignant tumors. We present a review of most of the unusual histological variants of cutaneous melanoma and describe their immunohistochemical features, associate clinical findings, and possible behavior related to the histological subtype. In addition, we propose their classification into four groups corresponding to the (1) architectural patterns; (2) cytologic features; (3) stromal changes; and (4) the possible association of these findings (i.e. architectural + cytologic features). Although most of these unusual variants have the same prognosis as conventional melanomas, with Breslow thickness and ulceration, being the most important predictor of survival in clinical stage I, some of them have a peculiar biologic behavior that the clinicians and the dermatopathologists should know in order to give melanoma patients all educational information available.

MR appearance of clear cell sarcoma of tendons and aponeuroses (malignant melanoma of soft parts): radiologic-pathologic correlation

Clear cell sarcoma of tendons and aponeuroses (CCSTA) is a rare aggressive soft tissue tumor that frequently produces melanin. Its MR findings are rarely described in the literature. We report the case of a previously healthy 54-year-old man with clear cell sarcoma of the thigh who presented with a large painless mass of 1 year's duration. MR imaging showed the tumor to be of high signal intensity on fast spin-echo and STIR images. Both fine needle aspiration and excisional biopsy showed abundant melanin pigments. Histologic diagnosis was compatible with CCSTA.

Lessons to be learned: a case study approach. Malignant melanoma of soft tissue

Malignant melanoma of soft tissue, also called clear cell sarcoma (CCS) of tendons and aponeuroses, presents as a soft tissue mass, usually in the lower extremity of young females. We report two cases of CCS of the upper extremity--in a Korean and a Saudi Arabian girl. Because of the presence of melanin, melanosomes, S-100 protein and the tendency for regional nodal metastases, it has been suggested that this entity be considered a melanoma rather than a soft tissue sarcoma. The evidence for a neuroectodermal origin of these neoplasms is compelling. Despite these features, CCS has been reported as showing a distinct chromosomal translocation pattern t(12;22)(q13;q12) in certain isolated cytogenetic or molecular diagnostic case reports; however, there is no information about the breakpoints at genomic level. Such genetic studies need to be performed on primary and metastatic cutaneous, mucosal or ocular melanomas prior to considering them specific for malignant melanoma of soft tissue/CCS. Microscopically, solid nests and fascicles of pale fusiform or cuboidal cells are divided by fine fibrous tissue septa. Characteristically, the cells possess a round to oval nucleus with a central prominent nucleolus. Pleomorphism may or may not be present; the cytoplasm is clear due to the presence of glycogen but, occasionally, the cytoplasm is more eosinophilic, resembling a melanoma. A tumour size (> or = 5 cm) and the presence of necrosis are statistically significant predictors of poor prognosis. A lesion on the proximal part of an extremity progresses slower than one that is more distal (i.e. acral). An early diagnosis and initial radical surgery are essential for a favourable clinical outcome. Once regional lymph node metastases or haematogenous dissemination has occurred, the prognosis becomes dismal.

Myxoid clear cell sarcoma

Clear cell sarcoma is a rare soft-tissue tumor presenting typically in the extremities of young adults. It has been also known as malignant melanoma of the soft parts because of the presence of melanin and cytoplasmic melanosomes. However, clear cell sarcoma is, at present, usually considered as a unique lesion because the t(12;22)(q13;q12) translocation is present only in clear cell sarcoma. Myxoid malignant melanoma is now a well-recognized morphologic variant of malignant melanoma. However, a myxoid variant of clear cell sarcoma has not been well described yet. We report a case of myxoid clear cell sarcoma occurring on the heel in a 22-year-old man. The tumor was composed of nests and fascicles of oval to fusiform cells with clear to pale eosinophilic cytoplasm, often separated by fibrous septa. The tumor cells were reactive for S-100 protein, HMB-45, and MART-1. Variably sized cysts lined by one or several layers of tumor cells were observed. Alcian blue and mucicarmine stains demonstrated prominent mucin deposition in the tumor stroma and especially in the lumen of the cysts. Fluorescence in situ hybridization for the Ewing sarcoma gene showed rearrangement in nearly all of the neoplastic cells.

Primary clear cell sarcoma of rib

Clear cell sarcoma (malignant melanoma of soft tissues) is a very rare soft tissue neoplasm. It generally arises in tendons and aponeuroses. Although metastasis of malignant melanoma to bone is not uncommon, primary clear cell sarcoma of bone is an extremely rare neoplasm. To our knowledge five cases have been reported in the English literature. We present a case of primary clear cell sarcoma of bone in a 28-year-old woman arising in the left ninth rib. We treated the patient with total excision of the mass and postoperative radiotherapy. The patient is alive and well without local recurrence or distant metastasis at 33 months after surgery.

Expression Profiling of t(12;22) Positive Clear Cell Sarcoma of Soft Tissue Cell Lines Reveals Characteristic Up-Regulation of Potential New Marker Genes Including ERBB3

Clear cell sarcoma of soft tissue (CCSST), also known as malignant melanoma of soft parts, represents a rare lesion of the musculoskeletal system usually affecting adolescents and young adults. CCSST is typified by a chromosomal t(12;22)(q13;q12) translocation resulting in a fusion between the Ewing sarcoma gene (EWSR1) and activating transcription factor 1 (ATF1), of which the activity in nontransformed cells is regulated by cyclic AMP. Our aim was to identify critical differentially expressed genes in CCSST tumor cells in comparison with other solid tumors affecting children and young adults to better understand signaling pathways regulating specific features of the development and progression of this tumor entity. We applied Affymetrix Human Genome U95Av2 oligonucleotide microarrays representing approximately 12,000 genes to generate the expression profiles of the CCSST cell lines GG-62, DTC-1, KAO, MST2, MST3, and Su-CC-S1 in comparison with 8 neuroblastoma, 7 Ewing tumor, and 6 osteosarcoma cell lines. Subsequent hierarchical clustering of microarray data clearly separated all four of the tumor types from each other and identified differentially expressed transcripts, which are characteristically up-regulated in CCSST. Statistical analysis revealed a group of 331 probe sets, representing approximately 300 significant (P < 0.001) differentially regulated genes, which clearly discriminated between the CCSST and other tumor samples. Besides genes that were already known to be highly expressed in CCSST, like S100A11 (S100 protein) or MITF (microphthalmia-associated transcription factor), this group shows an obvious portion of genes that are involved in cyclic AMP response or regulation, in pigmentation processes, or in neuronal structure and signaling. Comparison with other expression profile analyses on neuroectodermal childhood tumors confirms the high robustness of this strategy to characterize tumor entities based on their gene expression. We found the avian erythroblastic leukemia viral oncogene homologue 3 (ERBB3) to be one of the most dramatically up-regulated genes in CCSST. Quantitative real-time PCR and Northern blot analysis verified the mRNA abundance and confirmed the absence of the inhibitory transcript variant of this gene. The protein product of the member of the epidermal growth factor receptor family ERBB3 could be shown to be highly present in all of the CCSST cell lines investigated, as well as in 18 of 20 primary tumor biopsies. In conclusion, our data demonstrate new aspects of the phenotype and the biological behavior of CCSST and reveal ERBB3 to be a useful diagnostic marker.

Synovial Sarcoma of the Neck

BACKGROUND

Synovial sarcoma is a soft tissue sarcoma rarely seen in the head and neck. Due to its rarity and morphologic variations, diagnosis is difficult in most cases.

METHOD

A case of synovial sarcoma arising in the upper neck is presented. The detection of the specific chromosomal translocation t(X;18)(p11.2;q11.2) is also described.

RESULT

A specific chimeric gene, the SSX-SYT fusion gene, was identified in the formalin-fixed paraffin-embedded surgical specimen using the reverse-transcription polymerase chain reaction (RT-PCR) technique.

CONCLUSION

Synovial sarcoma contains a characteristic chromosomal translocation, which serves as a useful diagnostic tool. RT-PCR technique has enabled to detect this specific translocation not only in fresh tissues but also in archival paraffin-embedded specimens.

Congenital pauci-melanotic cellular blue nevus

Unusual or atypical melanocytic nevi can be confused with malignant melanoma. Two patients are presented here with a rare variant of melanocytic nevus. Both were men. One was 39 years old and sought medical attention after trauma of a "congenital mole". The other was 24 years old and presented with a history of a slowly growing lesion, which had been known since childhood. In both patients, the lesion occurred on the buttock. They were dermal and superficial subcutaneous nodules measuring 1.5 and 2.3 cm in greatest dimension, respectively. The tumors were composed of densely cellular fascicles of melanocytes arranged in a lobulated growth pattern. Rare nests of small epithelioid melanocytes were also seen. No melanin pigment was seen on hematoxylin and eosin-stained sections. Focal minimal pigment was noted by Fontana-Masson stain in one case. Involvement of numerous peripheral nerve trunks by fusiform melanocytes was a prominent feature. Rare mitotic figures were seen in melanocytes [1-2 mitoses per 50 high-power fields (HPF)]. The MIB-1 labeling index was low (less than 5% of the lesional cell population was immunopositive). Both tumors were excised with negative surgical margins. One patient underwent sentinel lymph node biopsy because there was controversy regarding the biologic potential of the lesion. No melanocytic tumor deposits were found in the lymph nodes. On clinical follow up of 11 years and 18 months after complete excision, both patients are alive and well with no evidence of recurrence. We regard these lesions as congenital monophasic and pauci-melanotic variants of cellular blue nevus. The nevi are presented here to enhance our knowledge of the morphologic spectrum of melanocytic tumors and to help avoid confusion with malignant melanoma.

Primary clear cell sarcoma (malignant melanoma) in the right radius

Clear cell sarcoma (malignant melanoma) originating in bone is an extremely rare occurrence, which has been reported twice previously. It is challenging to differentiate this neoplasm from skeletal metastasis of malignant melanoma because it shows no specific imaging, pathological or immunohistochemical features. However, this differentiation is clinically important due to significant differences in patient management. In this article, we present the case of a 55-year-old man with primary clear cell sarcoma arising in the right radius.

Molecular genetics of pediatric soft tissue tumors: clinical application

The application of molecular genetics to pediatric soft tissue tumors has grown tremendously over the last decade. It has resulted in the identification of novel genes that have provided us with an increased understanding of oncogenesis. Furthermore, these findings have identified diagnostic and potentially prognostic factors for patient management. Molecular diagnostic techniques, such as reverse transcription PCR (RT-PCR) and fluorescence in situ hybridization (FISH), have become important tools for evaluating pediatric soft tissue tumors. By detecting characteristic fusion genes, these techniques have greatly increased the diagnostic accuracy of histopathological classification. One of the exciting promises of the development of these molecular techniques is their ability to detect micrometastasis and minimal residual disease. Monitoring of minimal residual disease in pediatric soft tissue tumors by quantitative RT-PCR may provide important prognostic information. Furthermore, the potential development of targeted therapy based on the understanding of the molecular pathology of a specific soft tissue tumor may complement existing treatments and improve disease outcome.

Melanoma of the soft parts: diagnosis of metastatic and recurrent tumors by aspiration cytology

Three cases of melanoma of the soft parts diagnosed by aspiration cytology and immunochemistry are described. Unusual clinicoradiological features, variable cytomorphology, absence of melanin, and lack of awareness due to rarity of the lesion caused diagnostic dilemma. Morphological similarity to alveolar soft part sarcoma, synovial and epithelioid sarcoma, cutaneous melanoma, poorly differentiated carcinoma, and plasmacytoma were noted. Consideration of clinical data such as age, site, and radiology was helpful in narrowing down the diagnosis. A presumptive cytologic diagnosis helped in selecting the antibody panel, which established the definitive diagnosis in all cases. This approach is valuable in preoperative management and obviates the need for an open biopsy in primary, metastatic, or recurrent tumor. Increasing experience in fine-needle aspiration of this rare entity and correlation with immunochemistry and histopathology are valuable in narrowing down the differential diagnosis, reducing diagnostic errors, and widening its clinicocytological spectrum.

Clear cell sarcoma of the stomach

AIM

Clear cell sarcoma is a high-grade sarcoma with morphological features resembling malignant melanoma. This tumour is reported to display a characteristic distribution pattern nearly always involving the extremities. We report the first case of clear cell sarcoma of the stomach.

METHODS AND RESULTS

A 30-year-old male developed a huge tumour of the stomach, which at first glance could be considered as a poorly differentiated carcinoma. Immunohistochemical and ultrastructural examinations were consistent with a diagnosis of metastatic melanoma. However, cytogenetic examination revealed a t(12;22) translocation, specific for clear cell sarcoma. This was confirmed by fluorescence in-situ hybridization.

CONCLUSION

Making a reliable diagnosis of clear cell sarcoma of the stomach requires cytogenetic or molecular diagnostic investigations, particularly to rule out metastatic melanoma. This diagnosis avoids an unnecessary search for a primary melanoma.

Proteomic evaluation of archival cytologic material using SELDI affinity mass spectrometry: potential for diagnostic applications

Proteomic studies of cells via surface-enhanced laser desorption/ionization spectrometry (SELDI) analysis have enabled rapid, reproducible protein profiling directly from crude samples. We applied this technique to archival cytology material to determine whether distinct, reproducible protein fingerprints could be identifiedfor potential diagnostic purposes in blinded specimens. Rapid Romanowsky-stained cytocentrifuged specimens from fine-needle aspirates of metastatic malignant melanoma (with both known cutaneous primary and unknown primary sites), clear cell sarcoma, and renal cell carcinoma and reactive effusions were examined using the SELDI technology. A unique characteristic fingerprint was identified for each disease entity. Fifteen "blinded" unknown samples then were analyzed. When the protein profilefingerprints were plotted against the known fingerprints for the aforementioned diagnoses, the appropriate match or diagnosis was obtained in 13 (87%) of 15 cases. These preliminary findings suggest a substantial potential for SELDI applications to specific pathologic diagnoses.

Amelanotic cellular blue nevus: a hypopigmented variant of the cellular blue nevus: clinicopathologic analysis of 20 cases

Blue nevus and its variants typically present as pigmented lesions. Dermal melanin is responsible for coloration and is an expected histologic finding. Herein, we report 20 cases of an unusual amelanotic variant of cellular blue nevus. Our series showed clinical demographics similar to pigmented counterparts. Thus, there was a predilection for young individuals with a mean age of 24 years (range 6-74 years). Both sexes were affected, with a female-to-male ratio of approximately 2:1. The lower back, distal extremities, and scalp were the most common sites of occurrence. Importantly, the lack of pigmentation resulted in an atypical clinical appearance. A diagnosis of blue nevus by the attending physician was not considered in any of the reported lesions. All of the tumors extended deep into the reticular dermis or subcutaneous fat with a mean thickness of 5.5 mm (range 1.7-11 mm). Ulceration was present in two lesions. Mild cytologic atypia and pleomorphism were present in five cases. Mitotic activity (up to 3 mitoses/mm ) was observed in 11 lesions. A brisk lymphocytic host response was present in only one lesion. Tumor necrosis was not observed. Most, but not all, tumors showed reactivity for S-100 and HMB-45. Clinical follow-up (mean 32 months) was consistent with a benign course. Local recurrence was not observed after complete excision. None of the cases was associated with clinical evidence of lymph node or distant metastases. Recognition of amelanotic cellular blue nevus is important because the lack of expected pigmentation may result in clinical and pathologic diagnostic difficulty. In particular, amelanotic cellular blue nevus must be distinguished from malignant cellular blue nevus and other variants of melanoma.

Foot tumors: diagnosis and treatment

Several large clinical series have demonstrated that benign and malignant tumors occur in the foot and ankle at a much higher rate than previously thought. Vigilance is warranted in investigating any foot mass, including those with an apparently indolent course. Although tumors in the foot tend to produce symptoms relatively early because of the foot's compact structure, many tumors are initially misdiagnosed. Given the comparatively small size of the anatomic compartments in the foot, tumors often present outside the original compartment, making timely diagnosis essential. Major treatment errors can be avoided if physicians consider the potential for malignancy when evaluating all foot masses. A high index of suspicion, an organized approach to diagnosis, and evaluation of and adherence to the basic principles of treatment of musculoskeletal neoplasms increase the likelihood of acceptable results.

Chromosomal translocations and sarcomas

This review examines how the identification of tumor-specific translocations and fusion proteins has advanced the basic scientific and clinical understanding of sarcomas. Recent genetic advances, including the ASPL-TFE3 fusion of alveolar soft part sarcoma, the JAZF1-JJAZ1 fusion of endometrial stromal sarcoma, and HMGIC fusions in liposarcoma, are discussed. Next, the review addresses the ways in which molecular genetic data have influenced diagnostic and prognostic paradigms. For example, recent studies describe the detection of occult tumor cells and the identification of primary renal neoplasms that are genetically related to alveolar soft part sarcoma. In addition, the review discusses potential therapies based on the targeting of sarcoma-specific fusion proteins. These reports describe the potential use of Gleevec (STI571) for dermatofibrosarcoma protuberans and the use of tumor-specific fusion proteins as potential targets for immunotherapy. Finally, basic scientific findings are reviewed that elucidate, for example, the aberrant functions of SYT-SSX in chromatin remodeling and of EWS-FLI1 in transcription and mRNA splicing. These and other emerging models of tumorigenesis will help identify new therapeutic targets.

Clear cell sarcoma of tendons and aponeuroses in pediatric patients: a report from the Italian and German Soft Tissue Sarcoma Cooperative Group

BACKGROUND

Clear cell sarcoma (CCS) of tendons and aponeuroses is extremely rare in childhood and little information is available on its clinical management. Originally believed to be a type of melanoma of soft tissue origin, CCS is now considered a distinct clinicopathologic entity that behaves like a high-grade soft tissue sarcoma. We report on a series of 28 pediatric patients treated from 1980 to 2000 by the Soft Tissue Sarcoma Italian Cooperative Group and the German Cooperative Group.

METHODS

Patients were treated with a multimodality therapeutic approach. Surgical resection was complete in 17 patients (mutilating in 3), radiotherapy was administered to 8 patients, and 20 patients received chemotherapy.

RESULTS

After a median follow-up of 102 months (range, 19-238 months), the 5-year and event-free survival rates were 66.4% and 63.3%, respectively. Seventeen patients were alive in first remission, two were alive in second remission, and nine had died of disease. The response to chemotherapy in the 7 evaluable patients included one partial remission, one minor response, and five no responses. Radiotherapy contributed to achieving local control in four of six Intergroup Rhabdomyosarcoma Study (IRS) Group II patients. Statistically significant differences in outcome were evident according to IRS group, tumor size, and site.

CONCLUSIONS

Our study confirms the aggressive behavior of CCS. Complete surgical resection represents the mainstay of treatment, and even the only treatment for patients with small tumors. Radiotherapy may control microscopic residual disease after surgery. Chemotherapy is ineffective and the prognosis is unfavorable for patients with unresectable and large tumors.

Molecular genetic characterization of the EWS/ATF1 fusion gene in clear cell sarcoma of tendons and aponeuroses

Clear cell sarcoma (CCS) is a rare malignant soft tissue tumor particularly associated with tendons and aponeuroses. The cytogenetic hallmark is the translocation t(12;22)(q13;q12) resulting in a chimeric EWS/ATF1 gene in which the 3'-terminal part of EWS at 22q is replaced by the 3'-terminal part of ATF1 at 12q. To date, only 13 cases of CCS have been analyzed for fusion genes at the transcription level, and there is no information about the breakpoints at the genomic level. In the present study, we describe the molecular genetic characteristics of CCS from 10 patients. Karyotypes were obtained from 10 cases, 7 of which showed the characteristic t(12;22). As an initial step in the characterization of the EWS/ATF1 and ATF1/EWS chimeras, we constructed an exon/intron map of the ATF1 gene. The entire ATF1 gene spanned >40 kb and was composed of 7 exons. Intron 3, in which most of the genomic breakpoints occurred, was to a large extent (83%) composed of repetitive elements. RT-PCR amplified EWS/ATF1 cDNA fragments in all patients and ATF1/EWS cDNA fragments in 6 of 10 patients. Four types of EWS/ATF1 chimeric transcript, designated types 1-4, were identified. The most frequent chimeric transcript (type 1) was an in-frame fusion of exon 8 of EWS with exon 4 of ATF1. This was the only chimeric transcript in 5 patients but found together with other variants in 3 tumors. The type 2 transcript of EWS/ATF1, an in-frame fusion of exon 7 of EWS with exon 5 of ATF1, was detected in 4 patients, as the only transcript in 1 case and together with other variants in 3 cases. An in-frame fusion of exon 10 of EWS with exon 5 of ATF1 (type 3) was found in 1 patient as the only transcript, and an out-of-frame fusion of EWS exon 7 with ATF1 exon 7 (type 4) was detected in 1 patient together with type 1 and type 2 transcripts. Sequencing of the amplified ATF1/EWS cDNA fragments showed in 5 patients that ATF1 exon 3 was fused with EWS exon 10, resulting in an out-of-frame chimeric transcript. In 1 case, nt 428 of ATF1 (exon 4) was fused with EWS exon 8; at the junction, there was an insertion of 4 nucleotides, also resulting in an out-of-frame transcript. Genomic extra long PCR and sequence analysis mapped the genomic breakpoints to introns 7, 8 and 9 of EWS and intron 3 and exon 4 of ATF1. While a simple end-to-end fusion was observed in 2 cases, additional nucleotides were found at the junctions in 2 other cases. In addition, topoisomerase I consensus sequences were found close to the junctions, suggesting that this enzyme may participate in the genesis of the EWS/ATF1 fusion.