Clear-cell sarcoma of tendons and aponeuroses. An immunohistochemical and electron microscopic analysis indicating neural crest origin

Clear Cell Sarcoma of Soft Tissues: Radiological Analysis of 14 Patients-MRI Findings Related to Metastatic Disease

Background/Objectives: Clear cell sarcoma (CCS) is a very uncommon, aggressive soft-tissue sarcoma (STS) with a dismal prognosis. In the current literature, there are very limited data focused on the radiological features of CCS. Our study's objective was to describe CCS pre-treatment's peculiar imaging characteristics (MRI above all) and to assess if some radiologic features may predict patients' outcomes with regard to the occurrence of distant metastases. Methods: Our single-center experience includes all the patients with a histological diagnosis of CCS and available radiological and clinical data: 14 patients (8M, 6F, mean age 39.4 years old) were included. The available pre-treatment MRI or contrast-enhanced computed tomography (CECT) studies were examined using an analytical grid that incorporated characteristics from the most recent STS research. The occurrence of metastatic disease was matched with radiological features from baseline imaging studies. Results: MRI was available in 13 patients and CECT in 1 patient. The mean longest diameter (LD) was 50.5 mm ± 29.2. In 10 cases (71.4%), the tumor was deeply seated. MRI revealed a slightly high signal intensity (SI) on T1-WI and a high SI on T2-WI in every subject. At baseline, metastases were already present in 5/14 (35.7%) patients, 3 more developed metastases during the following 5 years (8/14, 57.1%), and 2 additional developed late-onset metastasis after more than 5 years from the diagnosis (total of 10/14 metastatic patients 71.4%). LD and metastasis at diagnosis were significantly correlated (Pearson correlation = 72%, p-value = 0.004). A pre-treatment LD > 4 cm was significantly associated with the development of distant metastases within 5 years from diagnosis and in subsequent follow-up (p = 0.0003). LD > 4 cm represents an increase in risk of metastatic disease within 5 years and during the course of follow-up (OR = 195.00, 95%CI: 3.36-11285.55, p = 0.01). The presence of MRI signs of macroscopic necrosis represented an increase in risk of metastatic disease within 5 years (OR = 15.00, 95%CI: 1.03-218.31-p = 0.04). Conclusions: The identification of MRI features of aggressive biology is a key element for an early referral to sarcoma centers. In our study, a LD > 4 cm and the presence of MRI signs of macroscopic necrosis at the baseline images resulted in being a predictor of metastatic disease.

Primary intraretinal clear cell sarcoma presenting as an amelanotic circumpapillary tumor

Purpose

To report a novel case of clear cell sarcoma presenting as an intraocular mass in a young adult female.

Observations

A 34-year-old female presented to the Retina Service as an emergency department referral for an intraocular lesion noted in the left eye. The patient endorsed progressively decreased vision in the left eye for three months duration. Fundus examination of the left eye was notable for a circumpapillary, retinal amelanotic mass with vitreous seeding. Due to concern for retinoblastoma and poor visual potential, the decision was made for primary enucleation. Initial histopathologic and immunohistochemical analyses demonstrated a primitive-appearing, epithelioid to spindled, intraretinal malignancy, with expression of all melanocytic markers by immunohistochemistry. Molecular genetic testing detected an EWSR1::ATF1 fusion. The patient was diagnosed with clear cell sarcoma of the eye and systemic work up revealed no additional disease burden.

Conclusions and importance

Clear cell sarcoma is a soft tissue sarcoma that can present within the eye and should be included in the differential diagnosis of amelanotic intraocular (intraretinal) tumors, including those in adults with clinical appearances similar to retinoblastoma.

Malignant melanoma: An important differential diagnosis for clear cell sarcoma of the gastrointestinal tract

A case report by Liu et al describes the characteristics of metastatic clear cell sarcoma (CCS) of the pancreas and provides valuable therapeutic insights for this rare malignancy. This case is interesting because of its rarity, suggesting that the pancreas may be a potential target organ for CCS, either primary or metastatic. At the same time, the authors also emphasize the importance of regular postoperative follow-up for timely detection of recurrent lesions, as CCS is characterized by a high degree of malignancy and a high rate of recurrent metastases. Considering that CCS of the gastrointestinal tract is easily confused with malignant melanoma (MM) of the gastrointestinal tract, here we compare the clinical features, histopathological and immunohistochemical characteristics, diagnosis, treatment, and prognosis of CCS and MM of the gastrointestinal tract, hoping to provide a reference for clinical work.

Clear cell sarcoma metastasizing to the pancreas

In this editorial based on a case report, we delve into a seldom-seen occurrence of clear cell sarcoma featuring pancreatic metastasis in a 47-year-old male patient. Recognized for its typical tendency to metastasize to the lungs, bones, and brain, clear cell sarcoma rarely extends its reach to the pancreas. Despite the initial absence of discernible abnormalities during the patient's physical examination, the manifestation of abdominal pain prompted further investigation. Subsequent abdominal computed tomography brought to light the presence of a pancreatic tumor, culminating in the definitive diagnosis of clear cell sarcoma with pancreatic metastasis. The successful management of this atypical presentation involved a series of surgical interventions, including distal pancreatectomy and splenectomy. This report not only sheds light on the infrequent manifestation of clear cell sarcoma within the pancreas but also underscores the pivotal role of vigilant postoperative follow-up in addressing this rare sarcoma. The emphasis on postoperative care serves as a crucial aspect of the broader narrative, acknowledging the need for ongoing monitoring and management to ensure a comprehensive and successful treatment trajectory for patients with this unique presentation of clear cell sarcoma.

Biological and therapeutic insights from animal modeling of fusion-driven pediatric soft tissue sarcomas

Survival for children with cancer has primarily improved over the past decades due to refinements in surgery, radiation and chemotherapy. Although these general therapies are sometimes curative, the cancer often recurs, resulting in poor outcomes for patients. Fusion-driven pediatric soft tissue sarcomas are genetically defined by chromosomal translocations that create a chimeric oncogene. This distinctive, almost 'monogenic', genetic feature supports the generation of animal models to study the respective diseases in vivo. This Review focuses on a subset of fusion-driven pediatric soft tissue sarcomas that have transgenic animal tumor models, which includes fusion-positive and infantile rhabdomyosarcoma, synovial sarcoma, undifferentiated small round cell sarcoma, alveolar soft part sarcoma and clear cell sarcoma. Studies using the animal models of these sarcomas have highlighted that pediatric cancers require a specific cellular state or developmental stage to drive tumorigenesis, as the fusion oncogenes cause different outcomes depending on their lineage and timing of expression. Therefore, understanding these context-specific activities could identify targetable activities and mechanisms critical for tumorigenesis. Broadly, these cancers show dependencies on chromatin regulators to support oncogenic gene expression and co-opting of developmental pathways. Comparative analyses across lineages and tumor models will further provide biological and therapeutic insights to improve outcomes for these children.

Modeling sarcoma relevant translocations using CRISPR-Cas9 in human embryonic stem derived mesenchymal precursors

The role of cancer relevant translocations in tumorigenesis has been historically hampered by the lack of faithful in vitro and in vivo models. The development of the latest genome editing tools (e.g., CRISPR-Cas9) allowed modeling of various chromosomal translocations with different effects on proliferation and transformation capacity depending on the cell line used and secondary genetic alterations. The cellular context is particularly relevant in the case of oncogenic fusions expressed in sarcomas whose histogenesis remain uncertain. Moreover, recent studies have emphasized the increased frequency of gene fusion promiscuity across different mesenchymal tumor entities, which are clinicopathologically unrelated. This review provides a summary of different strategies utilized to generate cancer models with a focus on fusion-driven mesenchymal neoplasia.

Gene fusions in superficial mesenchymal neoplasms: Emerging entities and useful diagnostic adjuncts

Cutaneous mesenchymal neoplasms are diagnostically challenging because of their overlapping morphology, and, often, the limited tissue in skin biopsy specimens. Molecular and cytogenetic techniques have identified characteristic gene fusions in many of these tumor types, findings that have expanded our understanding of disease pathogenesis and motivated development of useful ancillary diagnostic tools. Here, we provide an update of new findings in tumor types that can occur in the skin and superficial subcutis, including dermatofibrosarcoma protuberans, benign fibrous histiocytoma, epithelioid fibrous histiocytoma, angiomatoid fibrous histiocytoma, glomus tumor, myopericytoma/myofibroma, non-neural granular cell tumor, CIC-rearranged sarcoma, hybrid schwannoma/perineurioma, and clear cell sarcoma. We also discuss recently described and emerging tumor types that can occur in superficial locations and that harbor gene fusions, including nested glomoid neoplasm with GLI1 alterations, clear cell tumor with melanocytic differentiation and ACTIN::MITF translocation, melanocytic tumor with CRTC1::TRIM11 fusion, EWSR1::SMAD3-rearranged fibroblastic tumor, PLAG1-rearranged fibroblastic tumor, and superficial ALK-rearranged myxoid spindle cell neoplasm. When possible, we discuss how fusion events mediate the pathogenesis of these tumor types, and we also discuss the related diagnostic and therapeutic implications of these events.

Clear cell sarcoma: state-of-the art and perspectives

INTRODUCTION

Clear cell sarcoma (CCS) is an ultrarare soft tissue sarcoma (STS) with a poor prognosis due to its propensity to metastasize and its low chemosensitivity. The standard treatment of localized CCS consists of wide surgical excision with or without additive radiotherapy. However, unresectable CCS is generally treated with conventional systemic therapies available for treatment of STS despite the weak scientific evidence to support its use.

AREAS COVERED

In this review, we discuss the clinicopathologic characteristics of CSS, as well as the current treatment landscape and future therapeutic approaches.

EXPERT OPINION

The current treatment strategy of advanced CCSs, based on STSs regimens, shows a lack of effective options. Combination therapiesin particular, the association of immunotherapy and TKIs, represent a promising approach. Translational studies are needed in order to decipher the regulatory mechanisms involved in the oncogenesis of this ultrarare sarcoma and identify potential molecular targets.

Cutaneous melanocytic tumor with CRTC1::TRIM11 fusion and prominent epidermal involvement: A case report

Cutaneous melanocytic tumor with CRTC1::TRIM11 fusion (CMCT) is a recently described entity with only 13 cases reported in the literature. Histopathologically, the neoplasm consists of atypical epithelioid to spindled cells that form a well-circumscribed nodule confined to the dermis and subcutis with cytological features including large vesicular nuclei with prominent nucleoli and abundant eosinophilic cytoplasm. Immunohistochemistry shows variable expressivity of melanocytic markers. Currently, there is limited data regarding long-term outcomes of this newly described entity. Most cases have done well, but there is one case reported with an adverse event. Hence, further studies are needed to accurately classify this tumor. Definitive diagnosis is made by laboratory evidence of CRTC1::TRIM11 fusion. Herein, we report the first case of CMCT with epidermal involvement in the youngest patient known to be affected to date.

Nevus, melanoma or something else? Mesenchymal neoplasms with melanocytic differentiation

The overwhelming majority of cutaneous neoplasms with melanocytic differentiation are nevi, melanomas and more rarely melanocytomas. Nevertheless, there is also a group of mesenchymal neoplasms with genuine melanocytic differentiation which can create diagnostic difficulties with significant repercussions. These can rarely present as primary or metastatic cutaneous lesions. Theones that are relevant to a dermatopathologist include malignant melanotic nerve sheath tumor, perivascular epithelioid cell neoplasm and clear cell sarcoma. This work will provide a thorough review of clinical presentation, morphologic and immunohistochemical features as well as molecular pathogenesis of these tumors. We hope to familiarize the general dermatopathology readership with a group of neoplasms of mesenchymal lineage exhibiting melanocytic differentiation and ultimately avoid diagnostic misadventures. This article is protected by copyright. All rights reserved.

Ultrasound-based screening and characterization of an atypical clear-cell sarcoma of the hand: A case report

INTRODUCTION

Clear cell soft-tissue sarcoma is a rare tumor typically presenting in the lower extremities.

CASE PRESENTATION

We present a middle-aged woman with a 2-month history of a growing mass in the right hand dorsum. Initial biopsy reported findings consistent with benign fibroma, however, high-resolution ultrasound screening revealed a multilobulated, heterogeneous, and hypervascular mass highly suspicious for malignancy. Excisional biopsy, histology, and immunohistochemistry confirmed the diagnosis of clear-cell soft tissue sarcoma. The patient presented no evidence of recurrence at 6-month follow-up.

CONCLUSION

Ultrasound is an accessible and cost-effective modality for screening and management guidance for soft-tissue sarcomas.

Cytomorphological spectrum, including immunohistochemical results of 16 cases of clear cell sarcoma of soft tissue, along with positive EWSR1 gene rearrangement result in two cases

OBJECTIVES

To describe the cytopathological features of clear cell sarcomas (CCSs), including immunohistochemical and molecular results, the latter in selected cases.

METHODS

Sixteen consecutively diagnosed cases of CCS of soft tissue, over 6-year duration were included. Fine needle aspiration cytology was performed for primary diagnosis in three and for recurrent/metastatic lesions in 12 cases. Cytopathological features in 16 cases (conventional Papanicolaou- and May-Grünwald Giemsa-stained smears) were critically analysed. Corresponding histopathological and immunostained sections were available in 15 cases. Two cases were tested for EWSR1 gene rearrangement by fluorescence in-situ hybridisation.

RESULTS

Sixteen tumours occurred in patients with age ranging from 18 to 56 years (median = 33.5); M: F ratio = 1:1; in deep soft tissues, mostly in extremities. Primary cytopathological diagnosis (3 cases) was CCS with a differential diagnosis of melanoma (1 case) and poorly differentiated malignant tumour (2 cases). On review, smears were predominantly hypercellular (n = 14), invariably composed of monomorphic appearing epithelioid/polygonal cells (n = 16), including spindle cells (n = 6); mostly singly scattered (n = 16), in loose clusters (n = 12); with prominent nucleolisation (n = 16); granular to vacuolated, well-defined cytoplasm (n = 12), binucleation/multinucleation (n = 9); mitoses (n = 6); sudden anisonucleosis; racquet-shaped cells (n = 3), against a tigroid background (n = 2), along with focal intracytoplasmic pigment deposition (n = 2). Immunohistochemically, tumour cells were positive for S-100P (15/15), HMB-45 (15/15) and melan-A(6/12). Two cases tested for EWSR1 rearrangement displayed red-green split signals.

CONCLUSIONS

This constitutes one of the largest series describing the cytomorphological spectrum of CCS of soft tissue. Certain features, such as singly scattered monomorphic, epithelioid cells with prominent nucleolisation are useful diagnostic clues. Immunohistochemical stains are necessary and molecular testing is further helpful in reinforcing a diagnosis in certain cases. A correct diagnosis has crucial treatment implications.

Clear cell sarcoma-A review

Clear cell sarcoma (CCS) previously known as malignant melanoma (MM) of the soft tissue, although, similar in morphology to MM, contemporary histopathologic and cytogenetic techniques have made this diagnosis obsolete, as it is now possible to distinguish between CCS and MM. CCS is often diagnosed in young adults with median age of 25 years. Overall mortality is generally poor, and the 5-year survival is between 40 and 60%. Hence, early diagnosis and radical surgery are key in the treatment of this extremely rare malignancy of the soft tissue comprising only about 1% of all sarcomas. This article present an overview of this rare malignancy.

Significance of MRI in the diagnosis and differentiation of clear cell sarcoma of tendon and aponeurosis (CCSTA): A case report

RATIONALE

Clear cell sarcoma of tendon and aponeurosis (CCSTA) or soft parts is a rare malignant melanin producing tumor entity that is derived from the neural crest cells originating from soft tissues displaying melanocytic differentiation. Diagnosis of CCSTA is difficult as it is dependent on age, size, location, necrosis, calcifications, cystic degeneration, and local to distant metastatic deposits. These tumors have very poor prognosis with a survival rate of 5-10 years because of local recurrence, early to late metastasis to lymph nodes, lungs, bones, and liver.

PATIENT CONCERNS

A 30-year-old Asian male has presented with a painful mass in the posterior aspect of the right ankle. He recalled of noticing an increase in the size of the lump after a traumatic insult 3 months ago. Physical examination revealed a mass of size 9x4 cm in the posterior ankle with no cutaneous ulcerative lesions. There is no history of any longstanding illness or malignancy.

DIAGNOSES

Clear cell Sarcoma of Tendon and Aponeurosis (CCSTA) or CCS of Soft parts.

INTERVENTIONS

Conventional radiography demonstrated merely a soft tissue mass in the posterior compartment of the right ankle and significant calcaneal bone erosion with the sparse trabecular pattern. Plain conventional tomography showed a well-defined soft tissue heterogeneous mass with a hypoattenuating osteo-destructive focal lesion in the calcaneus. Magnetic resonance imaging (MRI) - T1 weighted imaging (T1WI) revealed an iso-intense signal relative to adjacent muscle; heterogeneous high-signal intensity on fat saturated T2 weighted imaging (T2WI). On contrast examination, lesion on T1WI, showed a heterogeneous high signal intensity, central low signal intensity with peripheral and septal enhancement. The immune-histochemistry analysis was positive for HMB-45, S-100, myoD1 and Ki67 (30%). Correlating with imaging and immune-histochemistry, a confirmatory diagnosis of CCSTA was made.

OUTCOMES

CCSTA is typically a slowly growing painless mass in the deep soft tissues of ear, pancreas, kidney, penis, abdomen, especially in the lower extremities- Achilles tendon and aponeurosis of the ankle or in foot of young adults. As, these tumors are highly malignant, difficult to diagnose, early recognition by imaging and surgical excision are the mainstay of management.

LESSONS

Our case emphasizes the importance of recognizing radiological characteristics of CCSTA, and its differentiation from other soft tissue tumors, when presenting atypically. MRI plays a significant role in the diagnosis supported by histopathology and immune-histochemistry. So, radiologists should be familiar about this presentation that could guide other personnel for early detection of soft tissue tumors while including CCSTA into differential diagnosis for evaluation.

Clear Cell Sarcoma of Tendons and Aponeuroses

Fifty-eight previously unreported cases of clear cell sarcoma of tendons and apo neuroses occurring in 29 males and 29 females with a median age of 31 years are presented. The distal extremities were most frequently involved (58%), followed by the limbs and limb girdles (33%), and trunk (9%). Median tumor size was 2.5 cm (range, 0.6-9 cm). Kaplan-Meier estimates revealed a 5-year survival rate of 63%. Eleven of 43 patients (26%) had local recurrences at a median interval of 33 months. Metastases occurred in 20 of 45 cases (44%) at a median interval of 26 months; 19 of 20 patients with metastases died of the disease. The most common metastatic site was the lungs (11 cases), followed by bone (9 cases), and lymph nodes (8 cases). Clear cell sarcoma had a stereotypic morphology consisting of packeted arrangements of uniform, round to fusiform cells with eosinophilic to clear glycogen-rich cytoplasm, and prominent nucleoli, as well as multinucleated tumor cells with a wreath-like arrangement of nuclei. S100 protein was detected in all 44 cases studied, vimentin in 36, and HMB45 stained 36. Twenty-six cases were studied with antibodies directed against proliferating cell nuclear antigen. Neither the intensity of proliferating cell nuclear antigen staining, percentage of positive cells, nor the combined score of these two variables corresponded with mitotic rate or survival. Increasing size (as a continu ous variable) and necrosis were found to be independent adverse prognostic factors by multivariate analysis. Int J Surg Pathol 1 (2):89-100, 1993

Prognostic factors associated with clear cell sarcoma in 14 Chinese patients

PURPOSE. To identify prognostic factors associated with clear cell sarcomas in 14 Chinese patients. METHODS. Medical records of 7 men and 7 women (mean age, 36 years) with histologically confirmed clear cell sarcoma of tendons and aponeuroses were reviewed. Patient demographics, tumour characteristics, and treatment modalities were retrieved. Prognostic factors associated with favourable 5-year survival were determined. RESULTS. The most affected sites were the thigh (n=5) and the foot (n=4); the mean time from symptom onset to diagnosis was 9.5 months. The tumour stage at diagnosis was IIA in 8 patients, IIB in 2, and III in 4. The mean tumour size was 4.5 cm in diameter. One patient was lost to follow-up. For the remaining 13 patients, the mean time to disease-related mortality was 2.5 years. Nine patients had distant metastases; the most common sites were lungs and pleura (n=7), followed by distant lymph nodes (n=4), bone (n=2), pericardium (n=2), and brain (n=1). All patients underwent surgical excision. Three women and one man (mean age, 27 years) attained 5-year disease-free survival. All had stage IIA tumours at diagnosis. Their mean tumour size was 1.75 cm in diameter, which was significantly smaller than that of all patients (4.5 cm). Tumour size of ≤ 2.5 cm in diameter (p=0.004) and stage IIA tumour at diagnosis (p=0.04) were significant prognostic factors for 5-year survival. CONCLUSION. Tumour size of ≤ 2.5 cm and early stage tumour are associated with 5-year disease-free survival. Early detection is crucial for the prognosis of clear cell sarcomas.

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.

Primary Clear Cell Sarcoma of the Tongue

Clear cell sarcoma shares features with melanoma, but frequently shows EWSR1 rearrangements. It is an aggressive tumor typically occurring in the soft tissues of the extremities, with a gastrointestinal variant with less consistent melanocytic differentiation. It is extremely rare in the head and neck region, with no reported cases in the oral cavity. We report a case of an 82-year-old woman with a clear cell sarcoma arising in the tongue, with cervical lymph node metastases. Histologically, the tumor showed some features of gastrointestinal clear cell sarcoma. No osteoclast-type giant cells were present. The tumor cells were positive for S100 protein and negative for other melanocytic markers. Fluorescence in situ hybridization showed rearrangements of EWSR1 and ATF1. This case expands the spectrum of clear cell sarcoma with a gastrointestinal-like variant in a novel site, emphasizing the need to consider it as a differential diagnosis to melanoma in mucosal sites.

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.

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.

Soft tissue tumors of uncertain origin

Many soft tissue tumors of childhood lack obvious differentiation toward a defined mesenchymal tissue type or have a phenotype that does not correspond to any defined normal tissue. These challenging tumors are currently regarded as neoplasms of uncertain differentiation. Nonetheless, there have been great strides in the understanding of their pathologic and genetic features and biologic underpinnings. The application of new genetic information to the pathologic diagnosis among this group of tumors is an emerging area in diagnostic pediatric pathology. This article reviews the clinicopathologic features of tumors of uncertain and/or miscellaneous origin, with an emphasis on the unique aspects of these neoplasms in children and adolescents, use of diagnostic adjuncts, and differential diagnosis.

Intra-abdominal clear-cell sarcoma: a report of 3 cases, including 1 case with unusual morphological features, and review of the literature

Clear-cell sarcoma (CCS) is a soft-tissue neoplasm that morphologically resembles cutaneous malignant melanoma but has a distinct molecular profile. Gastrointestinal and intra-abdominal CCSs are very rare. Here, the authors present 3 cases of intra-abdominal CCS and review the literature. Of these cases, 2 involved the small bowel, and 1 involved the peritoneum. Cases 1 and 3 had the characteristic CCS morphology, but case 2 was morphologically unusual and therefore difficult to diagnose. It had relatively small cells with less prominence of clear cells; many pseudoglandular structures were also present. It also showed aberrant expression of epithelial membrane antigen (EMA). The other 2 cases also involved some diagnostic uncertainty and were therefore referred to specialized centers. The authors wish to emphasize the importance of molecular studies in making a conclusive diagnosis of intra-abdominal CCS.

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.

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.

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 the ileum: report of a case and review of literature

Clear cell sarcoma (CCS) is a high grade soft tissue sarcoma with a distinct molecular profile and with morphological features resembling those of melanoma. CCS has been rarely described in other locations other than the soft tissues, including the gastrointestinal tract. In this study, we report a case of CCS arising in the ileum of a 31-year-old woman. Histologically, the tumor involved the entire thickness of the intestinal wall. Tumor cells were polygonal or fusiform, with clear or eosinophilic cytoplasm, arranged in a uniform nested to fascicular growth pattern. Immunohistochemical studies revealed strong positivity for vimentin and S-100 protein. HMB-45, Melan-A, tyrosinase, cytokeratins, EMA, smooth muscle actin, CD34, CD31, CD117, CD99, synaptophysin, chromogranin A, CD56, and NSE were negative. Fluorescence in situ hybridization analysis demonstrated the presence of a t(12;22)(q13;q12) translocation, the diagnostic hallmark of CCS of soft parts. The present case, together with a detailed review of the literature on this topic, demonstrates that the gastrointestinal tract is a possible site of CCS of soft tissues and that making a reliable diagnosis of this tumor requires cytogenetic or molecular diagnostic investigations.

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.

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.

Mismatch repair protein expression and microsatellite instability: a comparison of clear cell sarcoma of soft parts and metastatic melanoma

Clear cell sarcoma of soft parts is a rare soft tissue malignancy that shows phenotypic overlap with cutaneous melanoma but can be distinguished by the presence of a t(12;22) translocation. Microsatellite instability (MSI), a variation in the lengths of short repeat DNA segments in the genome, has been implicated in melanoma tumorigenesis, but is rare or absent in clear cell sarcoma. Defects in the mismatch repair (MMR) enzyme complex correlate with MSI in some tumor types, allowing the use of immunohistochemistry for the MMR proteins hMLH1 and hMSH2 to predict the presence of MSI. To determine if the association between MMR defects and MSI extends to clear cell sarcoma, we compared a group of nine clear cell sarcomas to 11 metastatic melanomas on the basis of MSI and the expression of MMR proteins. MSI was studied using fluorescence-based multiplexed PCR of five loci. Immunohistochemistry was evaluated on formalin-fixed paraffin-embedded tissue for hMLH1, hMHS2 and hMSH6. MSI was present in only 1/9 (11%) clear cell sarcoma case and in 8/11 (73%) melanoma cases. Immunostaining for hMLH1 and hMSH2 was preserved in all the clear cell sarcomas but loss of immunostaining for one or both proteins was seen in 6/11 melanomas (55%). hMSH6 was detected in 7/9 (78%) clear cell sarcomas and 10/11 (91%) of melanomas. Clear cell sarcoma and metastatic melanoma differed significantly with respect to the presence of MSI (P=0.010) and staining for hMLH1 and/or hMSH2 (P=0.014) but not hMSH6 (P=0.57). Mismatch repair, and consequently genomic instability may contribute to tumorigenesis in melanoma but not clear cell sarcoma. Immunostaining for hMLH1 and hMSH2 and MSI analysis may be helpful in the differential diagnosis of large soft tissue or visceral malignancies with melanocytic differentiation.

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.

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.

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.

EWS-ATF1 fusion transcripts in gastrointestinal tumors previously diagnosed as malignant melanoma

BACKGROUND

Clear cell sarcoma (CCS) is classically a deep soft tissue tumor associated with tendons or aponeuroses, although cases of primary CCS of the gastrointestinal (GI) tract have recently been reported. Because it is difficult to distinguish CCS from metastatic melanoma based on morphology, immunohistochemical profile, and ultrastructural features, it is possible that some GI tumors diagnosed as metastatic melanoma actually represent primary GI CCS. Because the EWS-ATF1 fusion transcript and the associated t(12;22)(q13;q12) translocation occur in CCS but not cutaneous melanoma, we investigated the use of molecular-based testing for discriminating CCS from metastatic melanoma (MM) in GI tumors.

METHODS

Patients with GI tumors diagnosed as MM were identified from departmental files. The tumors were tested for the EWS-ATF1 fusion transcript by RT-PCR and for t(12;22)(q13;q12) by fluorescence in situ hybridization.

RESULTS

Detailed review of medical records revealed that 16 (80%) of the 20 had a documented history of cutaneous melanoma. Two cases (10%) harbored the EWS-ATF1 fusion transcript, and fluorescence in situ hybridization confirmed the presence of t(12;22) in both cases. Of the 2 positive tumors, 1 developed in a patient who had no history of cutaneous melanoma, and the other developed in a patient with a remote history of vulvar melanoma.

CONCLUSION

Based on molecular genetic findings, a subset of GI tumors diagnosed as MM by routine histopathologic evaluation represents CCS.

Immunohistochemistry in the diagnosis of soft tissue tumours

Immunohistochemistry is particularly important in the field of soft tissue tumours because of their variety and the frequent difficulty of diagnosis. The first part of this paper discusses useful or new antibodies, together with others that are no longer of use. The second part is devoted to the role of immunohistochemistry in the diagnosis of soft tissue tumours: identification of some rare or atypical benign lesions, identification of non-mesenchymal malignant tumours, and classification of sarcomas. The respective roles of immunohistochemistry and molecular biology are underlined.

Classification of clear-cell sarcoma as a subtype of melanoma by genomic profiling

PURPOSE

To develop a genome-based classification scheme for clear-cell sarcoma (CCS), also known as melanoma of soft parts (MSP), which would have implications for diagnosis and treatment. This tumor displays characteristic features of soft tissue sarcoma (STS), including deep soft tissue primary location and a characteristic translocation, t(12;22)(q13;q12), involving EWS and ATF1 genes. CCS/MSP also has typical melanoma features, including immunoreactivity for S100 and HMB45, pigmentation, MITF-M expression, and a propensity for regional lymph node metastases.

MATERIALS AND METHODS

RNA samples from 21 cell lines and 60 pathologically confirmed cases of STS, melanoma, and CCS/MSP were examined using the U95A GeneChip (Affymetrix, Santa Clara, CA). Hierarchical cluster analysis, principal component analysis, and support vector machine (SVM) analysis exploited genomic correlations within the data to classify CCS/MSP.

RESULTS

Unsupervised analyses demonstrated a clear distinction between STS and melanoma and, furthermore, showed that CCS/MSP cluster with the melanomas as a distinct group. A supervised SVM learning approach further validated this finding and provided a user-independent approach to diagnosis. Genes of interest that discriminate CCS/MSP included those encoding melanocyte differentiation antigens, MITF, SOX10, ERBB3, and FGFR1.

CONCLUSION

Gene expression profiles support the classification of CCS/MSP as a distinct genomic subtype of melanoma. Analysis of these gene profiles using the SVM may be an important diagnostic tool. Genomic analysis identified potential targets for the development of therapeutic strategies in the treatment of this disease.

Establishment and characterisation of a human clear cell sarcoma model in nude mice

We have established a new experimental model of human clear cell sarcoma, UM-CCS1, using serial subcutaneous transplantation of intact tumour tissue in nude mice. The heterotransplanted nude mouse tumours retained characteristic morphological features of the primary clear cell sarcoma. Immunohistochemical analysis showed the retained expression patterns of S-100 protein, melanoma-associated antigen HMB-45 and vimentin in the xenografts as compared to the primary tumour. DNA index showed low variations both between the xenografts in the same passage and between the serial passages. Cytogenetic analysis of the primary tumour and the xenografts showed the unbalanced translocation der(6)t(6;12)(p23;q13). Based on the combined genetic data a reasonable interpretation of our findings is that there was a complex chromosomal rearrangement resulting in a cytogenetically cryptic EWS-ATF1 fusion gene. Analysis of cell kinetics using in vivo incorporation of iododeoxyuridine and flow cytometry showed generally short potential doubling time (T(pot)) of the xenografts. Volume doubling time showed low variations without correlation with T(pot). The retained phenotypic and genotypic characteristics of the primary tumour and the morphological and structural stability over time makes the model suitable for studies on the tumour biology and treatment of clear cell sarcoma.

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

Clear cell sarcoma (CCS), also known as melanoma of soft parts, is an uncommon deep soft tissue tumor presenting typically in the lower extremities of young adults. Previous cytogenetic studies have established the specificity of the recurrent t(12;22)(q13;q12), resulting in a EWS-ATF1 fusion, for CCS. The prevalence of the EWS-ATF1 fusion in CCS remains unclear, since most genetically confirmed CCS have been reported as isolated cytogenetic or molecular diagnostic case reports. We therefore studied histologically confirmed CCS from 12 patients for the presence of EWS-ATF1 by reverse-transcriptase polymerase chain reaction (RT-PCR), using RNA extracted from either frozen (four cases) or formalin-fixed paraffin-embedded (eight cases) material. All primary tumors were located in the deep soft tissues of the extremities. Histologically, 10 cases had a typical epithelioid nested appearance. Most or all cases showed immunostaining for HMB45 (12 of 12), S-100 protein (10 of 12), and MITF (12 of 12). Ultrastructural analysis showed melanosomes in six of seven cases. The presence of an EWS-ATF1 fusion transcript was identified by RT-PCR in 11 of 12 cases (91%), all of which showed the same fusion transcript structure, namely the previously described in-frame fusion of EWS exon 8 to ATF1 codon 65. RT-PCR analysis for the melanocyte-specific splice form of the MITF transcript was positive in all cases tested (4 of 4). These data confirm that EWS-ATF1 detection can be used as a highly sensitive diagnostic test for CCS and that CCS expresses the melanocyte-specific form of the MITF transcript, further supporting its genuine melanocytic differentiation.

Clear cell sarcoma: the Roswell Park experience

BACKGROUND AND OBJECTIVES

Clear cell sarcoma of the tendons and aponeuroses (CCSTA) is an aggressive, rare soft-tissue tumor with approximately 300 reported cases. Although it appears to be histogenetically related to melanoma, its clinical behavior resembles soft tissue sarcoma with a propensity for lymph node metastases. We report our experience at a tertiary cancer center.

METHODS

Eight cases of CCSTA evaluated at Roswell Park Cancer Institute between 1970 and 1998 were reviewed retrospectively. Patient data analyzed included patient age, gender, anatomic location, size of tumor, development of local, regional and distant recurrence, and patient status at last follow up.

RESULTS

Six of eight patients were alive at 2 years, while three of seven patients were alive at 5 years. Of the patients alive with no evidence of recurrence, two had tumors of less than 2 cm, and the remaining patient had incomplete information regarding tumor size. Five patients recurred within 2 years of definitive surgical management. Four had tumors > 5 cm. All five patients progressed to metastatic disease at a median follow up of 20 months (range 1-108 months) following definitive surgical management and all eventually died of their disease at a median of 3 months (range 0-24 months) from presentation with metastatic disease. Four of five patients with lesions > 5 cm received adjuvant chemotherapy with intent to cure, but all eventually died of disease at 4, 22, 34, and 41 months from initial presentation.

CONCLUSIONS

CCSTA is an aggressive tumor of the soft tissues. Early recognition and management are associated with an excellent long-term prognosis. Tumors greater than 5 cm warrant aggressive surgical management and treatment, and are at high risk of the development of distant disease. Aggressive multiagent chemotherapy appeared to have no impact on outcome. Other adjuvant therapeutic options including immunotherapy should be investigated.

[Clear cell sarcoma (malignant melanoma of soft tissues) of the calf ]

Clear cell sarcoma (malignant melanoma of soft parts) is a rare malignancy that is found in the young adult, and is generally located in the extremities of the limbs. In this study, a new case has been reported in a 24-year old male with no previous history of cutaneous melanoma. The tumor consisted of fusiform or round cells with clear or granulocytic cytoplasm and vesicular nuclei. The patient was treated by surgical resection of the tumor and postoperative radiotherapy. Eight years later, metastatic nodes were detected in the inguinal region. The histogenesis of this tumor has not yet been determined, and it poses a diagnostic problem for pathologists as it can be mistaken for a malignant metastatic cutaneous melanoma.

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

Clear cell sarcoma of tendons and aponeuroses (malignant melanoma of soft parts) and conventional malignant melanoma may demonstrate significant morphologic overlap at the light microscopic and ultrastructural level. Consequently, the clinically relevant distinction between primary clear cell sarcoma and metastatic melanoma in the absence of a known primary cutaneous, mucosal or ocular tumour may occasionally cause diagnostic problems. A balanced translocation, t(12;22)(q13;q13), which can be detected, amongst others, using the reverse transcriptase polymerase chain reaction (RT-PCR) or fluorescent in situ hybridization (FISH), has been identified in a high percentage (50-75%) of clear cell sarcomas and is presumed to be tumour specific. Whether this chromosomal rearrangement is present in malignant melanoma has, to date, not as yet been studied by molecular genetic or molecular cytogenetic techniques. Using RT-PCR and FISH, a series of metastases from 25 known cutaneous melanomas and 8 melanoma cell lines (5 uveal and 3 cutaneous) were screened for the t(12;22)(q13;q13) translocation. Primers for RT-PCR were chosen based upon published breakpoint sequences. The Cosmids G9 and CCS2.2, corresponding to the 5' region of EWS and 3' region of ATF-1 respectively, were used as probes. The translocation was not identified in any of the melanomas or melanoma cell lines analysed in this study; in contrast this translocation was identified in 3 out of 5 clear cell sarcomas using these techniques. This allows distinction between translocation positive cases of clear cell sarcoma and malignant melanoma at a molecular genetic level. Consequently, in diagnostically challenging cases, this represents a valuable tool for the clinicopathologic differentiation between these two entities, with an important impact on patient management and prognosis.

Clear cell sarcoma shows immunoreactivity for microphthalmia transcription factor: further evidence for melanocytic differentiation

Microphthalmia transcription factor, a melanocytic nuclear protein critical for the embryonic development and postnatal viability of melanocytes, is a master regulator in modulating extracellular signals. Recently, microphthalmia transcription factor expression was shown to be both a sensitive and specific marker of epithelioid melanoma. We investigated the sensitivity of D5, an anti-microphthalmia transcription factor antibody, for diagnosis of clear cell sarcoma (also known as malignant melanoma of soft parts). Immunoreactivity in a nuclear pattern for D5 was present in 8 of 12 (75%) tumors. D5 staining was strong in three tumors, moderate in two, and weak in three. S-100 protein expression was seen in all 12 cases that had clear cell sarcoma examined. HMB-45 staining was seen in 11 of 12 (92%) tumors. Focal Melan-A positivity was seen in 3 of 7 (43%) tumors. Although D5 was shown in a previous study to be a highly sensitive and specific marker for epithelioid melanomas, the results of this study expand the spectrum of tumors showing immunoreactivity for D5. D5 immunoreactivity in clear cell sarcoma provides further evidence for melanocytic differentiation in this unusual tumor.