Clear Cell Sarcomas of the Kidney registered on International Society of Pediatric Oncology (SIOP) 93-01 and SIOP 2001 protocols: A report of the SIOP Renal Tumour Study Group

Position paper: Rationale for the treatment of children with CCSK in the UMBRELLA SIOP-RTSG 2016 protocol

The International Society of Paediatric Oncology-Renal Tumour Study Group (SIOP-RTSG) has developed a new protocol for the diagnosis, treatment, and follow-up monitoring of childhood renal tumours - the UMBRELLA SIOP-RTSG 2016 protocol (the UMBRELLA protocol). This protocol has been designed to continue international collaboration in the treatment of childhood renal tumours and will be implemented in over 50 different countries. Clear cell sarcoma of the kidney, which is a rare paediatric renal tumour that most commonly occurs in children between 2 and 4 years of age, is specifically addressed in the UMBRELLA protocol.

Dysregulated mitogen-activated protein kinase signalling as an oncogenic basis for clear cell sarcoma of the kidney

The oncogenic mechanisms and tumour biology underpinning clear cell sarcoma of the kidney (CCSK), the second commonest paediatric renal malignancy, are poorly understood and currently, therapy depends heavily on doxorubicin with cardiotoxic side-effects. Previously, we characterized the balanced t(10;17)(q22;p13) chromosomal translocation, identified at that time as the only recurrent genetic aberration in CCSK. This translocation results in an in-frame fusion of the genes YWHAE (encoding 14-3-3ϵ) and NUTM2, with a somatic incidence of 12%. Clinico-pathological features of that cohort suggested that this aberration might be associated with higher stage and grade disease. Since no primary CCSK cell line exists, we generated various stably transfected cell lines containing doxycycline-inducible HA-tagged YWHAE-NUTM2, in order to study the effect of expressing this transcript. 14-3-3ϵ-NUTM2-expressing cells exhibited significantly greater cell migration compared to isogenic controls. Gene and protein expression studies were indicative of dysregulated MAPK/PI3K-AKT signalling, and by blocking these pathways using neutralizing antibodies, the migratory advantage conferred by the transcript was abrogated. Importantly, CCSK tumour samples similarly show up-regulation/activation of these pathways. These results support the oncogenic role of 14-3-3ϵ-NUTM2 in CCSK and provide avenues for the exploration of novel therapeutic approaches. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

High-dose treatment for malignant rhabdoid tumor of the kidney: No evidence for improved survival-The Gesellschaft für Pädiatrische Onkologie und Hämatologie (GPOH) experience

BACKGROUND

Malignant rhabdoid tumor of the kidney (MRTK) is the most aggressive childhood renal tumor with overall survival (OS) rates ranging from 22% to 42%. Whether high-dose chemotherapy with autologous stem-cell transplantation (HDSCT) in an intensive first-line treatment offers additional benefit is an ongoing discussion.

METHODS

A retrospective analysis of all 58 patients with MRTK from Austria, Switzerland, and Germany treated in the framework of consecutive, prospective renal/rhabdoid tumor studies SIOP9/GPO, SIOP93-01/GPOH (where SIOP is International Society of Pediatric Oncology and GPOH is German Society of Pediatric Oncology and Hematology), SIOP2001/GPOH, and European Rhabdoid Tumor Registry from 1991 to 2014.

RESULTS

Median age at diagnosis was 11 months. Fifty percent of patients had metastases or multifocal disease at diagnosis (Stage IV). Local stage distribution was as follows: not done/I/II/III-1/6/11/40. Fifteen (26%) patients underwent upfront surgery. Thirty-seven (64%) patients achieved a complete remission, 17 (29%) relapsed, 34 (59%) died of disease progression, and two (3%) died of treatment-related complication. Mean time to the first event was 3.5 months. Two-year EFS/OS (where EFS is event-free survival) for the whole group was 37 ± 6%/38 ± 6%. Metastases/multifocal disease, younger age, and local stage III were associated with significantly inferior survival. Eleven (19%) patients underwent HDSCT (carboplatin + thiotepa, n = 6; carboplatin + etoposide + melphalan, n = 4; others, n = 1); 2-year OS in this group was 60 ± 15% compared to 34 ± 8% in the non-HDSCT group (P = 0.064). However, the time needed from radiologic to histologic diagnosis, stem-cell harvest, and HDSCT must also be taken into account to avoid selection bias by excluding the highest risk group with early progression (<90 days). Thus, 2-year EFS only for patients without progression until day 90 was 60 ± 16% consolidated by HDSCT compared to 62 ± 11% without (P = 0.8).

CONCLUSION

Our retrospective analysis suggests comparable outcomes for patients with and without HDSCT, if adjusted for early disease progression.

CNS high-grade neuroepithelial tumor with BCOR internal tandem duplication: a comparison with its counterparts in the kidney and soft tissue

Central nervous system high-grade neuroepithelial tumors with BCOR alteration (CNS HGNET-BCOR) are a recently reported rare entity, identified as a small fraction of tumors previously institutionally diagnosed as so-called CNS primitive neuroectodermal tumors. Their genetic characteristic is a somatic internal tandem duplication in the 3' end of BCOR (BCOR ITD), which has also been found in clear cell sarcomas of the kidney (CCSK) and soft tissue undifferentiated round cell sarcomas/primitive myxoid mesenchymal tumors of infancy (URCS/PMMTI), and these BCOR ITD-positive tumors have been reported to share similar pathological features. In this study, we performed a clinicopathological and molecular analysis of six cases of CNS HGNET-BCOR, and compared them with their counterparts in the kidney and soft tissue. Although these tumors had histologically similar structural patterns and characteristic monotonous nuclei with fine chromatin, CNS HGNET-BCOR exhibited glial cell morphology, ependymoma-like perivascular pseudorosettes and palisading necrosis, whereas these features were not evident in CCSK or URCS/PMMTI. Immunohistochemically, diffuse staining of Olig2 with a mixture of varying degrees of intensity, and only focal staining of GFAP, S-100 protein and synaptophysin were observed in CNS HGNET-BCOR, whereas these common neuroepithelial markers were negative in CCSK and URCS/PMMTI. Therefore, although CNS HGNET-BCOR, CCSK and URCS/PMMTI may constitute a group of BCOR ITD-positive tumors, only CNS HGNET-BCOR has histological features suggestive of glial differentiation. In conclusion, we think CNS HGNET-BCOR are a certain type of neuroepithelial tumor relatively close to glioma, not CCSK or URCS/PMMTI occurring in the CNS.

TCF21 hypermethylation regulates renal tumor cell clonogenic proliferation and migration

We recently identified hypermethylation at the gene promoter of transcription factor 21 (TCF21) in clear cell sarcoma of the kidney (CCSK), a rare pediatric renal tumor. TCF21 is a transcription factor involved in tubular epithelial development of the kidney and is a candidate tumor suppressor. As there are no in vitro models of CCSK, we employed a well-established clear cell renal cell carcinoma (ccRCC) cell line, 786-O, which also manifests high methylation at the TCF21 promoter, with consequent low TCF21 expression. The tumor suppressor function of TCF21 has not been functionally addressed in ccRCC cells; we aimed to explore the functional potential of TCF21 expression in ccRCC cells in vitro. 786-O clones stably transfected with either pBABE-TCF21-HA construct or pBABE vector alone were functionally analyzed. We found that ectopic expression of TCF21 in 786-O cells results in a trend toward decreased cell proliferation (not significant) and significantly decreased migration compared with mock-transfected 786-O cells. Although the number of colonies established in colony formation assays was not different between 786-O clones, colony size was significantly reduced in 786-O cells expressing TCF21. To investigate whether the changes in migration were due to epithelial-to-mesenchymal transition changes, we interrogated the expression of selected epithelial and mesenchymal markers. Although we observed upregulation of mRNA and protein levels of epithelial marker E-cadherin in clones overexpressing TCF21, this did not result in surface expression of E-cadherin as measured by fluorescence-activated cell sorting and immunofluorescence. Furthermore, mRNA expression of the mesenchymal markers vimentin (VIM) and SNAI1 was not significantly decreased in TCF21-expressing 786-O cells, while protein levels of VIM were markedly decreased. We conclude that re-expression of TCF21 in renal cancer cells that have silenced their endogenous TCF21 locus through hypermethylation results in reduced clonogenic proliferation, reduced migration, and reduced mesenchymal-like characteristics, suggesting a tumor suppressor function for transcription factor 21.

Aberrant epigenetic regulation in clear cell sarcoma of the kidney featuring distinct DNA hypermethylation and EZH2 overexpression

The global methylation profile and the mutational status of 633 specific epigenetic regulators were analyzed in the pediatric tumor clear cell sarcoma of the kidney (CCSK). Methylation array analyses of 30 CCSKs revealed CCSK tumor DNA to be globally hypermethylated compared to Wilms tumor, normal fetal kidney, and adult kidney. The aberrant methylation pattern of CCSKs was associated with activation of genes involved in embryonic processes and with silencing of genes linked to normal kidney function. No epigenetic regulator was recurrently mutated in our cohort, but a mutation in the key epigenetic regulator EZH2 was discovered in one case. EZH2 mRNA was significantly higher in CCSK compared to Wilms tumor and normal kidney, and the EZH2 protein was strongly expressed in more than 90 % of CCSK tumor cells in 9/9 tumors analyzed. This was in striking contrast to the lack of EZH2 protein expression in Wilms tumor stromal elements, indicating that EZH2 could be explored further as a diagnostic marker and a potential drug target for CCSK.

Primary Renal Sarcomas With BCOR-CCNB3 Gene Fusion: A Report of 2 Cases Showing Histologic Overlap With Clear Cell Sarcoma of Kidney, Suggesting Further Link Between BCOR-related Sarcomas of the Kidney and Soft Tissues

We report 2 primary renal sarcomas demonstrating BCOR-CCNB3 gene fusions that have recently been identified in undifferentiated round cell sarcomas of bone and soft tissue. These neoplasms occurred in male children aged 11 and 12 years, and both were cystic as a result of entrapment and dilatation of native renal tubules. Both cases were composed of variably cellular bland spindle cells with fine chromatin set in myxoid stroma and separated by a branching capillary vasculature. Both neoplasms demonstrated immunoreactivity for BCOR, cyclin D1, TLE1, and SATB2 in the spindle neoplastic cells and negativity in the prominent capillary vasculature. One case was extensively cystic and had hypocellular areas that simulated cystic nephroma; this neoplasm recurred 3 years later as a solid, highly cellular spindle cell sarcoma in the abdominal cavity. The morphology and immunoprofile of these renal neoplasms was compared with a control group of other sarcomas with BCOR genetic abnormalities, including clear cell sarcoma of the kidney (CCSK), infantile undifferentiated round cell sarcomas of soft tissue/primitive myxoid mesenchymal tumor of infancy, and bone/soft tissue sarcomas with BCOR-CCNB3 gene fusion; along with primary renal synovial sarcoma. Our findings show that the renal sarcomas with BCOR-CCNB3 gene fusion overlap with CCSK. These results are in keeping with a "BCOR-alteration family" of renal and extrarenal neoplasms which includes CCSK and undifferentiated round cell sarcomas of soft tissue/primitive myxoid mesenchymal tumor of infancy (which typically harbor BCOR internal tandem duplication), and BCOR-CCNB3 sarcomas, all of which are primarily driven by BCOR overexpression and have overlapping (but not identical) clinicopathologic features.

Recurrent BCOR Internal Tandem Duplication and YWHAE-NUTM2B Fusions in Soft Tissue Undifferentiated Round Cell Sarcoma of Infancy: Overlapping Genetic Features With Clear Cell Sarcoma of Kidney

Soft tissue undifferentiated round cell sarcoma (URCS) occurring in infants is a heterogenous group of tumors, often lacking known genetic abnormalities. On the basis of a t(10;17;14) karyotype in a pelvic URCS of a 4-month-old boy showing similar breakpoints with clear cell sarcoma of kidney (CCSK), we have investigated the possibility of shared genetic abnormalities in CCSK and soft tissue URCS. Most CCSKs are characterized by BCOR exon 16 internal tandem duplications (ITDs), whereas a smaller subset shows YWHAE-NUTM2B/E fusions. Because of overlapping clinicopathologic features, we have also investigated these genetic alterations in the so-called primitive myxoid mesenchymal tumor of infancy (PMMTI). Among the 22 infantile URCSs and 7 PMMTIs selected, RNA sequencing was performed in 5 and 2 cases, with frozen tissue, respectively. The remaining cases with archival material were tested for YWHAE-NUTM2B/E by fluorescence in situ hybridization (FISH) or reverse transcription-polymerase chain reaction (RT-PCR), and BCOR ITD by PCR. A control group of 4 CCSKs and 14 URCSs in older children or adults without known gene fusion and 20 other sarcomas with similar histomorphology or age at presentation were also tested. A YWHAE-NUTM2B fusion was confirmed in the index case by FISH and RT-PCR, whereas BCOR ITD was lacking. An identical YWHAE-NUTM2B fusion was found in another URCS case of a 5-month-old girl with a back lesion. The remaining cases and control group lacked YWHAE gene rearrangements; instead, consistent BCOR ITDs, similar to CCSK, were found in 15/29 (52%) infantile sarcoma cases (9/22 infantile URCS and 6/7 PMMTI). In the control cohort, BCOR ITD was found only in 3 CCSK cases but not in the other sarcomas. Histologically, URCS with both genotypes and PMMTI shared significant histologic overlap, with uniform small blue round cells with fine chromatin and indistinct nucleoli. A prominent capillary network similar to CCSK, rosette structures, and varying degree of myxoid change were occasionally seen. BCOR ITD-positive tumors occurred preferentially in the somatic soft tissue of the trunk, abdomen, and head and neck, sparing the extremities. RNAseq showed high BCOR mRNA levels in BCOR ITD-positive cases, compared with other URCSs. In summary, we report recurrent BCOR exon 16 ITD and YWHAE-NUTM2B fusions in half of infantile soft tissue URCS and most PMMTI cases, but not in other pediatric sarcomas. These findings suggest a significant overlap between infantile URCS and CCSK, such as age at presentation, histologic features, and genetic signature, thus raising the possibility of a soft tissue counterpart to CCSK.

Renal Tumors of Childhood: Radiologic-Pathologic Correlation Part 1. The 1st Decade: From the Radiologic Pathology Archives

Wilms tumor is the second most common pediatric solid tumor and by far the most common renal tumor of infants and young children. As most tumors are large at presentation and are treated with nephrectomy, the role of imaging is primarily in preoperative planning and evaluation for metastatic disease. However, with treatment protocols increasingly involving use of preoperative (neoadjuvant) chemotherapy (the standard in Europe) and consideration of nephron-sparing surgery, the role of imaging is evolving to include providing initial disease staging information and a presumptive diagnosis to guide therapy. Differential diagnostic considerations include lesions that are clinically benign and others that require more intensive therapy than is used to treat Wilms tumor. In part 1 of this article, the unique histologic spectrum of renal neoplasms of infants and young children is reviewed with emphasis on radiologic-pathologic correlation. Part 2 will focus on renal tumors of older children and adolescents.

Biology and treatment of renal tumours in childhood

In Europe, almost 1000 children are diagnosed with a malignant renal tumour each year. The vast majority of cases are nephroblastoma, also known as Wilms' tumour (WT). Most children are treated according to Société Internationale d'Oncologie Pédiatrique Renal Tumour Study Group (SIOP-RTSG) protocols with pre-operative chemotherapy, surgery, and post-operative treatment dependent on stage and histology. Overall survival approaches 90%, but a subgroup of WT, with high-risk histology and/or relapsed disease, still have a much poorer prognosis. Outcome is similarly poor for the rare non-WT, particularly for malignant rhabdoid tumour of the kidney, metastatic clear cell sarcoma of the kidney (CCSK), and metastatic renal cell carcinoma (RCC). Improving outcome and long-term quality of life requires more accurate risk stratification through biological insights. Biomarkers are also needed to signpost potential targeted therapies for high-risk subgroups. Our understanding of Wilms' tumourigenesis is evolving and several signalling pathways, microRNA processing and epigenetics are now known to play pivotal roles. Most rhabdoid tumours display somatic and/or germline mutations in the SMARCB1 gene, whereas CCSK and paediatric RCC reveal a more varied genetic basis, including characteristic translocations. Conducting early-phase trials of targeted therapies is challenging due to the scarcity of patients with refractory or relapsed disease, the rapid progression of relapse and the genetic heterogeneity of the tumours with a low prevalence of individual somatic mutations. A further consideration in improving population survival rates is the geographical variation in outcomes across Europe. This review provides a comprehensive overview of the current biological knowledge of childhood renal tumours alongside the progress achieved through international collaboration. Ongoing collaboration is needed to ensure consistency of outcomes through standardised diagnostics and treatment and incorporation of biomarker research. Together, these objectives constitute the rationale for the forthcoming SIOP-RTSG 'UMBRELLA' study.

[Clear cell sarcoma of kidney in children]

Clear cell sarcoma of the kidney (CCSK) is a rare tumor that is diagnosed most often in children between 2- and 4-years-old of age. Usually, patients with CCSK are treated in international study for intrarenal tumors, preferentially Wilms tumor, according to bad histopronostic group. The purpose of this paper is to review the most important features in 2015 about epidemiology, radiology, anatomopathology and genetic of CCSK, and above all a synthesis about successive treatment strategies with their results. Second most common pediatric renal tumor in children less than 5-years-old, its prognosis has improved dramatically in recent years with the use of anthracyclines.

The clinical phenotype of YWHAE-NUTM2B/E positive pediatric clear cell sarcoma of the kidney

Clear cell sarcoma of the kidney (CCSK) although uncommon, is the second most frequent renal malignancy of childhood. Until now, the sole recurrent genetic aberration identified in CCSKs is t(10;17)(q22;p13), which gives rise to a fusion transcript of YWHAE and NUTM2B/E. So far, the clinical relevance of this fusion transcript is unknown. The aim of this descriptive study was to determine the clinical phenotype of t(10;17)(q22;p13) positive CCSKs. Snap-frozen tissues, formalin-fixed paraffin-embedded tissues or RNA previously extracted from CCSK samples throughout European, North-American and Japanese study groups were screened by RT-PCR for the YWHAE-NUTM2B/E transcript. Clinical characteristics, tumor characteristics, and outcome of patients with and without the fusion transcript were studied. The cohort comprised 51 previously published cases to which were added 139 internationally collected CCSK samples. RNA from 57 of these additionally collected cases was of sufficient quality to be successfully screened for the YWHAE-NUTM2B/E transcript. In total, seven of the 108 cases harbored the fusion transcript. Patients with tumors containing the fusion transcript were relatively young (median age 10 months), had associated low median tumor volumes and stage I disease was not observed in these patients. Two of seven patients relapsed and one of seven patients died of disease. Ranges of values were not overtly different between patients with and without the fusion transcript; however, the number of fusion transcript positive cases turned out to be too small to permit reliable statistical analysis. The current study did not identify an explicit clinical phenotype of CCSK cases harboring the YWHAE-NUTM2B/E fusion transcript.

Whole transcriptome sequencing identifies BCOR internal tandem duplication as a common feature of clear cell sarcoma of the kidney

PURPOSE

Clear cell sarcoma of the kidney (CCSK) is a rare pediatric renal tumor that is frequently difficult to distinguish among other childhood renal tumors due to its histological heterogeneity. This work evaluates genetic abnormalities carried by a series of CCSK samples by whole transcriptome sequencing (WTS), to identify molecular biomarkers that could improve the diagnostic process.

METHODS

WTS was performed on tumor RNA from 8 patients with CCSK. Bioinformatic analysis, with implementation of a pipeline for detection of intragenic rearrangements, was executed. Sanger sequencing and gene expression were evaluated to validate BCOR internal tandem duplication (ITD).

RESULTS

WTS did not identify any shared SNVs, Ins/Del or fusion event. Conversely, analysis of intragenic rearrangements enabled the detection of a breakpoint within BCOR transcript recurrent in all samples. Three different in-frame ITD in exon15 of BCOR, were detected. The presence of the ITD was confirmed on tumor DNA and cDNA, and resulted in overexpression of BCOR.

CONCLUSIONS

WTS coupled with specific bioinformatic analysis is able to detect rare genetic events, as intragenic rearrangements. ITD in the last exon of BCOR is recurrent in all CCSK samples analyzed, representing a valuable molecular marker to improve diagnosis of this rare childhood renal tumor.

Recurrent internal tandem duplications of BCOR in clear cell sarcoma of the kidney

The X-linked BCL-6 co-repressor (BCOR) gene encodes a key constituent of a variant polycomb repressive complex (PRC) that is mutated or translocated in human cancers. Here we report on the identification of somatic internal tandem duplications (ITDs) clustering in the C terminus of BCOR in 23 of 27 (85%) pediatric clear cell sarcomas of the kidney (CCSK) from two independent cohorts. We profile CCSK tumours using a combination of whole-exome, transcriptome and targeted sequencing. Identical ITD mutations are found in primary and relapsed tumour pairs but not in adjacent normal kidney or blood. Mutant BCOR transcripts and proteins are markedly upregulated in ITD-positive tumours. Transcriptome analysis of ITD-positive CCSKs reveals enrichment for PRC2-regulated genes and similarity to undifferentiated sarcomas harbouring BCOR–CCNB3 fusions. The discovery of recurrent BCOR ITDs defines a major oncogenic event in this childhood sarcoma with significant implications for diagnostic and therapeutic approaches to this tumour.

The genetic basis of clear cell sarcomas of the kidney is not well understood. In this study, Roy et al. perform whole-exome and RNA sequencing of these tumours and identify recurrent internal tandem duplications in BCOR, a key constituent of a variant polycomb repressive complex.

BCOR internal tandem duplication and YWHAE-NUTM2B/E fusion are mutually exclusive events in clear cell sarcoma of the kidney

Clear cell sarcoma of the kidney (CCSK) is the second most common pediatric renal tumor. Two recurrent genetic aberrations have been described in CCSK. One is a fusion of YWHAE and NUTM2B/E, the other is an internal tandem duplication (ITD) in the BCOR gene. Here it is shown that YWHAE-NUTM2B/E fusion and the BCOR ITD are mutually exclusive events and activated different downstream signaling systems. This has important diagnostic implications and opens up for further mechanistic studies of CCSK pathogenesis.

TCF21 hypermethylation in genetically quiescent clear cell sarcoma of the kidney

Clear Cell Sarcoma of the Kidney (CCSK) is a rare childhood tumor whose molecular pathogenesis remains poorly understood. We analyzed a discovery set of 13 CCSKs for changes in chromosome copy number, mutations, rearrangements, global gene expression and global DNA methylation. No recurrent segmental chromosomal copy number changes or somatic variants (single nucleotide or small insertion/deletion) were identified. One tumor with t(10;17)(q22;p13) involving fusion of YHWAE with NUTM2B was identified. Integrated analysis of expression and methylation data identified promoter hypermethylation and low expression of the tumor suppressor gene TCF21 (Pod-1/capsulin/epicardin) in all CCSKs except the case with t(10;17)(q22;p13). TARID, the long noncoding RNA responsible for demethylating TCF21, was virtually undetectable in most CCSKs. TCF21 hypermethylation and decreased TARID expression were validated in an independent set of CCSK tumor samples. The presence of significant hypermethylation of TCF21, a transcription factor known to be active early in renal development, supports the hypothesis that hypermethylation of TCF21 and/or decreased TARID expression lies within the pathogenic pathway of most CCSKs. Future studies are needed to functionally verify a tumorigenic role of TCF21 down-regulation and to tie this to the unique gene expression pattern of CCSK.

Consistent in-frame internal tandem duplications of BCOR characterize clear cell sarcoma of the kidney

Clear cell sarcoma of the kidney (CCSK) is one of the major pediatric renal neoplasms, but its associated genetic abnormalities are largely unknown. We identified internal tandem duplications in the BCOR gene (BCL6 corepressor) affecting the C terminus in 100% (20/20) of CCSK tumors but in none (0/193) of the other pediatric renal tumors. CCSK tumors expressed only an aberrant BCOR allele, indicating a close correlation between BCOR aberration and CCSK tumorigenesis.

Bilateral clear cell sarcoma of the kidney

Clear cell sarcoma of the kidney (CCSK) accounts for 2-5% of all pediatric renal malignancies, and is known for its propensity to metastasize to bone and other sites. We are reporting two cases with bilateral CCSK that were diagnosed at our institution. One patient initially presented with bilateral renal masses, as well as pulmonary, hepatic and bone metastasis; while other present only with bilateral masses with no evident distant metastasis. Both patients received aggressive neo-adjuvant chemotherapy to decrease tumor size. One patient completed his designated treatment and initially showed complete remission (CR); eventually suffering from relapse. The other patient's tumor progressed during the course of chemotherapy. Both cases manifested brain dissemination at the time of relapse or progression. This emphasizes the importance of staging stratification in CCSK. This also illustrates CCSK's ability to metastasize to bone and other sites including the brain (a primary relapse site in our cases).

An approach to renal masses in pediatrics

Renal masses in children may be discovered during routine clinical examination or incidentally during the course of diagnostic or therapeutic procedures for other causes. Renal cancers are rare in the pediatric population and include a spectrum of pathologies that may challenge the clinician in choosing the optimal treatment. Correct identification of the lesion may be difficult, and the appropriate surgical procedure is paramount for lesions suspected to be malignant. The purpose of this article is to provide a comprehensive overview regarding the spectrum of renal tumors in the pediatric population, both benign and malignant, and their surgical management.

Clear cell sarcoma of the kidney: patients' characteristics and improved outcome in developing countries

BACKGROUND

Clear cell sarcoma of the kidney (CCSK) is a rare and aggressive tumor accounting for 5% of pediatric renal tumors with an incidence of 20 patients per year in the USA. It is bone metastasizing with poor prognosis. Our aim was to show characteristics of patients in relation to improved outcome in one of the developing countries.

PROCEDURE

We included all patients diagnosed as CCSK in the period between July 2007 and March 2012 at Children's Cancer Hospital, Egypt. Patients' demographics, clinical presentation, pathology, and management were reviewed. Follow up was continued until April 2013.

RESULTS

Twenty-five patients were identified in the defined time interval, accounting for 7% all renal tumors diagnosed at the hospital. Mean age was 36 months. Abdominal swelling and hematuria were the most common presentations. Stages I, II, III, IV, and V represented 9 (36%), 3 (12%), 8 (32%), 3 (12%), and 2 (8%), respectively. Twenty-four patients had radical nephrectomy either upfront or after neo-adjuvant chemotherapy. Surgery was followed by adjuvant chemotherapy. Abdominal radiotherapy was given for local stages II and III. Twenty-two patients reached complete remission, while one patient had stationary disease and two patients died due to progression and relapse. Overall survival was 88.5% and event-free survival was 87.8% at 45 months.

CONCLUSION

Although previous studies indicate poor prognosis of CCSK, our experience shows that those patients can be treated using extensive chemotherapy combined with proper local control.

Clear cell sarcoma of the kidney in a child with Fanconi anemia

Patients with Fanconi anemia subgroup D1, attributable to biallelic mutations in BRCA2, have an increased risk of solid tumors. Tumors in the kidneys of these patients are almost exclusively Wilms tumor. We report the first recorded case, to our knowledge, of a Clear Cell Sarcoma of the Kidney in a patient with this cancer predisposition syndrome. We review different aspects of the need for careful clinical observation in patients of this complementation group, given their risk for malignancy.

Treatment and outcome of patients with relapsed clear cell sarcoma of the kidney: a combined SIOP and AIEOP study

Background:

Clear cell sarcoma of the kidney (CCSK) is an uncommon paediatric renal tumour. Relapses occur in about 15% of the patients. Since detailed clinical information on relapsed CCSK is scarce, the current study aims to describe outcome of patients with relapsed CCSK treated according to recent European protocols.

Patients and methods:

We analysed prospectively collected data of all CCSK patients who developed a relapse after complete remission at the end of primary treatment, entered onto SIOP and AIEOP trials between 1992 and 2012.

Results:

Thirty-seven of 237 CCSK patients (16%) treated according to SIOP and AIEOP protocols developed a relapse. Median time from initial diagnosis to relapse was 17 months (range, 5.5 months - 6.6 years). Thirt-five out of thirty-seven relapses (95%) were metastatic; the most common sites of relapse were the brain (n=13), lungs (n=7) and bone (n=5). Relapse treatment consisted of chemotherapy (n=30), surgery (n=19) and/or radiotherapy (n=18), followed by high-dose chemotherapy and autologous bone marrow transplantation (ABMT) in 14 patients. Twenty-two out of thirty-seven patients (59%) achieved a second complete remission (CR); 15 of whom (68%) developed a second relapse. Five-year event-free survival (EFS) after relapse was 18% (95% CI: 4%–32%), and 5-year overall survival (OS) was 26% (95% CI: 10%–42%).

Conclusions:

In this largest series of relapsed CCSK patients ever described, overall outcome is poor. Most relapses are metastatic and brain relapses are more common than previously recognised. Intensive treatment aiming for local control, followed by high dose chemotherapy and ABMT, seems to be of benefit to enhance survival. Novel development of targeted therapy is urgently required.

Stage I clear cell sarcoma of the kidney: is it the time for a less intensive adjuvant treatment?

Clear cell sarcoma of the kidney (CCSK) is a rare type of renal tumor, comprising 2% to 5% of all primary renal tumors in children. Despite the label of "unfavorable" tumor, with recent multimodality treatment schedules, including radiotherapy and multi-agent chemotherapy, disease free survival rates approaching 80% can be achieved. Younger age at tumor diagnosis and advanced-stage disease represent adverse prognostic factors. Of note, as a consequence of oncologic therapies a number of surviving patients have suffered from late sequelae on the musculoskeletal, gastrointestinal, hepatic, endocrine and cardiovascular function, or developed second tumors. Improved survival rates and a deeper knowledge of iatrogenic complications have promoted the awareness of a sequential reduction of treatment intensity, at least for low-stage CCSK, above all focusing on the abolition of flank radiation therapy (RT). It is fundamental to recognize that the rarity of this tumor calls for international cooperation trough controlled clinical trials, and without forgetting the key importance of a correct histological diagnosis and adequate surgical staging. The recent recognition of CCSK specific chromosomal translocation might help to guide targeted therapies complementary to conventional chemotherapy and radiotherapy.

Pediatric genitourinary oncology

Tumors of the kidney, bladder, prostate, testis, and adrenal represent a large part of the adult urologic practice, but are relatively infrequent in children. The natural history and management of these tumors in the pediatric age is different from that of the adults. As result of the successful work of several clinical trial groups in recent decades, there has been a significant improvement in their cure rates. The aim of this article is to review their most significant clinical aspects, as well as to present an update in their management.