Clear cell sarcoma of the kidney with emphasis on ultrastructural studies

Clear Cell Sarcoma of the Kidney

Clear cell sarcoma of the kidney is an uncommon malignant pediatric renal neoplasm that typically presents in the 2- to 3-year age group and has a propensity for aggressive behavior and late relapses. Histologically, this tumor exhibits a great diversity of morphologic patterns that can mimic most other pediatric renal neoplasms, often leading to confusion and misdiagnosis. Until recently, adjunct immunohistochemical and molecular genetic tests to support the diagnosis were lacking. The presence of internal tandem duplications in BCL-6 coreceptor (BCOR) and a translocation t(10;17) creating the fusion gene YWHAE-NUTM2B/E have now been well accepted. Immunohistochemistry for BCOR has also been shown to be a sensitive and specific marker for clear cell sarcoma of the kidney in the context of pediatric renal tumors. Improved intensive chemotherapy regimens have influenced the clinical course of the disease, with late relapses now being less frequent and the brain having overtaken bone as the most common site of relapse.

Clear Cell Sarcoma of the Kidney

Clear cell sarcoma of the kidney is the second most common primary renal malignancy in childhood. It is histologically diverse, making accurate diagnosis challenging in some cases. Recent molecular studies have uncovered BCOR exon 15 internal tandem duplications in most cases, and YWHAE-NUTM2 fusion in a few cases, with the remaining cases having other genetic mutations, including BCOR-CCNB3 fusion and EGFR mutations. Although clear cell sarcoma of the kidney has no specific immunophenotype, several markers including cyclin D1, nerve growth factor receptor, and BCOR (BCL6 corepressor) have emerged as potential diagnostic aides. This review provides a concise account of recent advances in our understanding of clear cell sarcoma of the kidney to serve as a practical update for the practicing pathologist.

Imputing gene expression to maximize platform compatibility

Microarray measurements of gene expression constitute a large fraction of publicly shared biological data, and are available in the Gene Expression Omnibus (GEO). Many studies use GEO data to shape hypotheses and improve statistical power. Within GEO, the Affymetrix HG-U133A and HG-U133 Plus 2.0 are the two most commonly used microarray platforms for human samples; the HG-U133 Plus 2.0 platform contains 54 220 probes and the HG-U133A array contains a proper subset (21 722 probes). When different platforms are involved, the subset of common genes is most easily compared. This approach results in the exclusion of substantial measured data and can limit downstream analysis. To predict the expression values for the genes unique to the HG-U133 Plus 2.0 platform, we constructed a series of gene expression inference models based on genes common to both platforms. Our model predicts gene expression values that are within the variability observed in controlled replicate studies and are highly correlated with measured data. Using six previously published studies, we also demonstrate the improved performance of the enlarged feature space generated by our model in downstream analysis.

Availability and Implementation

The gene inference model described in this paper is available as a R package (affyImpute), which can be downloaded at http://simtk.org/home/affyimpute.

Contact

rbaltman@stanford.edu.

Supplementary information

Supplementary data are available at Bioinformatics online.

Primary renal sclerosing epithelioid fibrosarcoma: report of 2 cases with EWSR1-CREB3L1 gene fusion

We report the first 2 genetically confirmed cases of primary renal sclerosing epithelioid fibrosarcoma (SEF), occurring in a 17-year-old boy and a 61-year-old woman. In both cases, the tumors demonstrated the typical epithelioid clear cell morphology associated with extensive hyalinizing fibrosis, raising the differential diagnosis of solitary fibrous tumor, metanephric stromal tumor, and the sclerosing variant of clear cell sarcoma of the kidney. Both neoplasms demonstrated diffuse immunoreactivity for MUC4, a highly specific marker for SEF, and both demonstrated evidence of rearrangement of both the EWSR1 and CREB3L1 genes, which have recently been shown to be fused in this entity. Both neoplasms presented with metastatic disease. Primary renal SEF represents yet another translocation-associated sarcoma now shown to arise primarily in the kidney.

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.

Outcome of pediatric renal tumor treated using the Japan Wilms Tumor Study-1 (JWiTS-1) protocol: a report from the JWiTS group

PURPOSE

In 1996, the Japan Wilms Tumor Study (JWiTS) group was founded to elucidate the efficacy and safety of the regimen established by the National Wilms Tumor Study (NWTS) group in the USA, and a multicenter cooperative study (JWiTS-1) was started in Japan. This report reviews the results of JWiTS-1.

METHODS

A total of 307 patients with malignant renal tumor were enrolled in the JWiTS-1 study between 1996 and 2005. Central pathological diagnosis and follow-up data were available in 210 cases. The protocol regimens were similar to the NWTS-5 regimens. Clinical stage was classified according to the Japanese Staging System.

RESULTS

Five-year overall survival (OS) rate was 91.1% for nephroblastoma, 72.9% for clear cell sarcoma of the kidney (CCSK), and 22.2% for rhabdoid tumor of the kidney (RTK). In the nephroblastoma patients, 5-year OS was 90.5% for stage I disease, 92.2% for stage II, 90.9% for stage III, 86.7% for stage IV, and 78.7% for stage V.

CONCLUSIONS

The OS of patients in the JWiTS-1 study were comparable with the results of other multicenter studies in the USA and Europe. The outcome for patients with nephroblastoma and CCSK was fair. In contrast, the cure rate for those with RTK was not satisfactory. New treatment strategies are needed for patients with RTK.

Pediatric Renal Neoplasms

Renal tumors in childhood consist of a diverse group of tumors ranging from the most common Wilms' tumor, to the uncommon and often fatal rhabdoid tumor. Diagnosis is based on morphologic features and aided by ancillary techniques such as immunohistochemistry and cytogenetics. Molecular techniques have helped identify a group of pediatric renal cell carcinomas that have specific translocations, called translocation-associated carcinomas. Differential diagnosis of the various tumors is discussed. Pathogenesis and nephroblastomatosis, the precursor lesions of Wilms tumor, also are discussed briefly, as are the handling of these tumor specimens and prognostic factors.

Current therapy for Wilms' tumor

Wilms' tumor was the first solid malignancy in which the value of adjuvant chemotherapy was established. Multimodality treatment has resulted in a significant improvement in outcome from approximately 30% in the 1930s to more than 85% in the modern era. Although the National Wilms' Tumor Study Group and the International Society of Pediatric Oncology differ philosophically regarding the merits of preoperative chemotherapy, outcomes of patients treated with either up-front nephrectomy or preoperative chemotherapy have been excellent. The goal of current clinical trials is to reduce therapy for children with low-risk tumors, thereby avoiding acute and long-term toxicities. At the same time, current clinical trials seek to augment therapy for patients with high-risk Wilms' tumor, including those with bilateral, anaplastic, and recurrent favorable histology tumors.

Complete response of recurrent cellular congenital mesoblastic nephroma to chemotherapy

Congenital mesoblastic nephroma (CMN) is usually cured by surgery. The sensitivity of this tumor to chemotherapy is unknown. The recent description of a t(12;15)(p13;q25) chromosomal translocation in both cellular CMN and congenital infantile fibrosarcoma suggests that these entities have a common pathogenesis, and that cellular CMN might respond to chemotherapy like congenital infantile fibrosarcoma does. The authors describe three patients with recurrent cellular CMN who showed a complete response to chemotherapy. Based on these patients and a review of the literature, the authors suggest that chemotherapy be considered as a part of the therapy for recurrent or unresectable cellular CMN.

Functional and gene expression analysis of the p53 signaling pathway in clear cell sarcoma of the kidney and congenital mesoblastic nephroma

Mutation of p53 has been implicated in progression of classical Wilms tumor (WT) into the anaplastic variant (AWT), drug resistance, and poor prognosis. Because of prognostic similarities, clear cell sarcoma of the kidney (CCSK) has been classified with AWT and other aggressive pediatric renal tumors, apart from congenital mesoblastic nephroma (CMN), which is instead a relatively benign tumor of neonates. Initially, CCSK and CMN were assumed to be ontologically related, but the role of p53 in the pathogenesis of either disease has not been sufficiently evaluated as in AWT. We examined the status of p53 in CMN and CCSK in comparison to AWT by immunohistochemistry and mRNA analysis of p53, the downstream effector p21(WAF-1/CIP-1) ( p21), the multidrug resistance gene MDR-1, a putative target of p53, and the p53-antagonist Mdm-2. Surprisingly, strong p53 nuclear immunoreactivity was found in cultures from two CMN specimens, but not in frozen or fixed tumor tissue from five other CMN specimens, nor in cell lines or tumor tissue from CCSK. Sequence analysis excluded p53 mutations. The size of the p53 mRNA in CMN and CCSK primary tumors excluded gross deletions or rearrangements. Low levels of Mdm-2 mRNA in CCSK and CMN primary tumors and cultures did not support a role for Mdm-2. Absence of MDR-1 mRNA excluded MDR-1 in the drug-resistant phenotype of CCSK. Cisplatin-induced p21 transactivation assays and G(1) cell cycle arrest analyses showed that p21 transactivation and G(1) arrest occurred in both CCSK and CMN cultures, demonstrating integrity of the p53 signal transduction pathway. Absence of p53 functional abnormalities excluded relationships between CCSK and CMN as in AWT, supporting the association of cellular CMN with congenital fibrosarcomas as more recently proposed.

Ovarian sarcoma with pathologic features of clear cell sarcoma of the kidney

We report a case of an unusual sarcoma arising in the ovary of an infant girl. Histologically, the tumor was composed of clear, undifferentiated cells set in an arborizing vascular stroma. Immunohistochemical staining was positive only for vimentin. Ultrastructural evaluation demonstrated undifferentiated cells with interdigitating broad cell processes that encompassed irregular electron lucent spaces that contained flocculent extracellular material. Light and electron microscopic features of the tumor resembled a clear cell sarcoma of the kidney. Although the cell of origin is unproven, both tumors may arise from primitive mesenchymal cells that may not be restricted to the kidney.

Comparative genomic hybridization analysis of clear cell sarcoma of the kidney

BACKGROUND

Clear cell sarcoma of the kidney (CCSK) is a rare malignant pediatric tumor, distinguished from the Wilms tumor by its characteristic histologic features and a more aggressive clinical behavior with a tendency to metastasize to bone. Genetic studies on CCSK are limited and no consistent findings have been reported.

PROCEDURE

We examined four cases of CCSK for presence of consistent genetic alterations using comparative genomic hybridization (CGH). This is the first report concerning CGH analysis of CCSK.

RESULTS

Three of the tumors showed no chromosome gains or losses. One of the tumors had gains of 1 q and the terminal end of 11 q.

CONCLUSIONS

These results are consistent with previous findings of limited chromosomal changes in CCSK karyotypes. Gain of 1 q in CCSK warrants further investigation. Copy number gains of 1 q have been repeatedly demonstrated in soft tissue and bone sarcomas, as well as other tumors, implying the presence of genes involved in tumor development and/or progression.

Clear cell sarcoma of the kidney: a review of 351 cases from the National Wilms Tumor Study Group Pathology Center

We reviewed 351 cases of clear cell sarcoma of the kidney (CCSK), including 182 cases entered on National Wilms Tumor Study Group (NWTSG) trials 1-4 for which clinical follow-up information was available. Tumors were restaged using NWTS 5 criteria. Mean age at diagnosis in the NWTS group was 36 months with a range of 2 months to 14 years. The male to female ratio was 2:1. Typical gross features included large size (mean diameter 11.3 cm), a mucoid texture, foci of necrosis, and prominent cyst formation. Nine major histologic patterns were identified (classic, myxoid, sclerosing, cellular, epithelioid, palisading, spindle, storiform, and anaplastic); virtually all tumors contained multiple patterns that blended with one another. Immunohistochemical stains were performed on 45 cases; only vimentin was consistently immunoreactive. Consistently negative results with other antibodies helped exclude other tumors in the differential diagnosis; all CCSKs were cytokeratin-negative, including epithelioid tumors that mimicked Wilms tumor, and MIC2-negative, including cellular tumors that mimicked primitive neuroectodermal tumor. The p53 gene product was rarely overexpressed in non-anaplastic CCSKs, but strikingly overexpressed in two of three anaplastic CCSKs. Overall survival was 69%. Multivariate analysis revealed four independent prognostic factors for survival: treatment with doxorubicin, stage, age at diagnosis, and tumor necrosis. Of note, stage 1 patients had a remarkable 98% survival rate. No other histologic or clinical variable independently correlated with survival.

Clear cell sarcoma of kidney in an adolescent and in young adults: a report of four cases with ultrastructural, immunohistochemical, and DNA flow cytometric analysis

Clear cell sarcoma of the kidney is a distinct, highly malignant pediatric neoplasm. Its occurrence in adults is extremely rare and the subject of isolated case reports. We present a series of four cases (three males and one female) identified in an adolescent and in young adults (16, 18, 20, and 25 years) with flank mass (three cases), hematuria (two cases), flank pain (two cases), and hypertension (one case). Three patients had stage III disease and one had stage I disease (National Wilms' Tumor Study staging system). All tumors had predominantly or exclusively the classic histology of a monotonous proliferation of uniform small round cells with evenly distributed fine chromatin, although focal microcyst formation (two cases) and spindled architecture (one case) (variant patterns) were also noted. Therapy in all cases consisted of surgery and chemotherapy with or without radiation. Follow-up data (29-202 months) showed distant metastases in all four cases, including the lung (four cases), bone (two cases), and the liver (two cases). Three patients died of disease at 29, 59, and 63 months (mean, 50.3 months), and one patient is alive with no evidence of disease at 202 months. Ultrastructural features included scattered primitive junctions, short and irregular cytoplasmic extensions, and scant to a moderate amount of mitochondria. Immunohistochemical study (three cases) showed immunoreactivity with vimentin (two cases) and no reaction with cytokeratin, epithelial membrane antigen, S-100 protein, or desmin. Flow cytometric analysis showed diploid DNA content in three primary tumors and tetraploidy in one metastatic tumor. The proliferative activity (S-phase fraction) was low to intermediate (mean, 9.8%). Our data suggest that clear cell sarcoma of the kidney in the young adult age group resembles its pediatric counterpart in ultrastructural and immunohistochemical characteristics, proclivity for skeletal and visceral metastasis, DNA diploid status with relatively low S-phase, and aggressive clinical course. Clear cell sarcoma of the kidney in adult patients, although rare, must be differentiated from sarcomatoid carcinoma, sarcomas, and round cell tumors because of its unique characteristics in comparison to other renal neoplasms.

[Clear cell renal carcinoma outside of the usual age group]

We report a case of a 17 year old woman with a clear cell sarcoma of kidney treated at the Division of Urology of Hospital General de Agudos Dr. José M. Ramos Mejía dependent of Government of Buenos Aires City. This report is based on the unusual age of tumor presentation and its good course and results after radiotherapy and chemotherapy, with 10 years survival after surgery.

Pediatric renal tumors

A broad spectrum of renal tumors occurs in infants and children ranging from the benign cystic nephroma to the extremely aggressive malignant rhabdoid tumor of the kidney. A thorough understanding of these tumors is crucial to the optimal diagnosis and management of children with renal masses. The common renal tumors in infants and children are discussed and an orderly method for their evaluation is presented. Recent developments in the molecular biology of Wilms' tumor are outlined to provide insight into the origin of this tumor.

Clear cell sarcoma of the kidney: an unusual presentation and review of the literature

PURPOSE

To describe a child with clear cell sarcoma of the kidney (CCSK) with an unusual presentation, including a primary tumor of the left kidney with metastases to the right kidney and soft tissues of the lower extremities, and to review the literature.

PATIENT AND METHODS

An 8-month-old infant presented with hypertension, an abdominal mass, and soft tissue masses in the left thigh and right foot. Imaging studies revealed a large left-sided renal tumor, left paravertebral soft tissue masses, and left thigh mass. At laparotomy, a lesion was noted in the lower pole of the contralateral kidney. CCSK with metastases to the contralateral kidney and to the soft tissues of left thigh, right foot, and left paravertebral region was diagnosed on histopathologic examination.

RESULTS

Multimodal oncologic treatment included surgery, chemotherapy, and radiotherapy. Three months after completion of therapy, a soft tissue lesion in the left arm and, later, soft tissue lesions involving multiple parts of the body developed. The patient died 18 months after diagnosis without clinical or radiographic evidence of bone involvement.

CONCLUSIONS

In a review of the literature, CCSK is most commonly associated with bone and lung metastases. Soft tissue involvement is uncommon. Metastasis to the contralateral kidney at initial diagnosis has not previously been reported. This case represents an unusual metastatic pattern of CCSK.

Renal neoplasms of childhood

Wilms' tumor is the most common childhood renal tumor. This article describes the epidemiology, histopathologic features, and clinical manifestations of Wilms' tumor along with the spectrum of imaging findings using different modalities. The distinguishing features of other renal tumors encountered in children, such as clear cell sarcoma, rhabdoid tumor, congenital mesoblastic nephroma, multilocular cystic renal tumor, renal cell carcinoma, and angiomyolipoma are also reviewed.

Late recurrence of clear cell sarcoma of the kidney

Clear cell sarcoma of the kidney (CCSK) is a rare pediatric neoplasm with particular propensity for bone metastasis that requires aggressive therapy. We report a patient with CCSK who was misreported as having Wilm's tumour at the time of initial diagnosis and received only minimal therapy. The disease recurred locally-after 8 years, with no evidence of distant metastasis. Important clinical and histologic features of CCSK are described, along with a review of the literature.

Clear cell sarcoma of the kidney in an adult

An adult case of clear cell sarcoma of the kidney is described. The clinical, histological, immunohistochemical and electron microscopical features of the tumour are described.

Nephrogenic rest associated with a mesoblastic nephroma--what does it tell us?

A 3-year-old girl presented with a tumor in the right kidney that was found to be a mesoblastic nephroma on histological examination. In addition, between the tumor and renal parenchyma there was a large perilobar sclerosing nephrogenic rest--a finding that has rarely been reported previously in non-Wilms renal tumors of childhood. We believe this supports the theory that both mesoblastic nephroma and Wilms tumor arise from the developing kidney but the key difference is the time point at which induction of neoplasm occurs.

Bone metastasizing renal tumor of childhood. A clinicopathological study of eleven cases from the Prague Pediatric Tumor Registry

Eleven patients with bone metastasizing renal tumor of childhood (BMRTCh) who were diagnosed and treated in our departments over a 20-year period were reviewed. The incidence among all malignant renal tumors in children up to 15 years of age in our files was 3.7%. The male to female ratio was 10:1. The morphology had a uniform, predominantly clear cell finely vascularized pattern in all of them. Various previously recognized variations of the classic pattern such as hyalinization, nuclear palisading and cyst formation were observed in some patients. Electron microscopy showed that coarse vacuolization of the tumor seen at the light microscopic level was due to distended extracellular spaces surrounded by tumor cells and their cytoplasmic processes. Immunohistochemistry of the tumor cells revealed positive vimentin in all cases, and focally positive muscle specific actin in one. A prominent feature was fascicles of perivascular spindle cells. They were considered to be tumor cells rather than stromal elements since their morphology was close to the appearance of the polygonal tumor cells. The follow up data were available for ten patients. Four developed bone metastases, three of them died of the disease progression. Another patient died of lymph node dissemination and gastrointestinal bleeding. Six patients survived for a period of 29 months to 14 years following the diagnosis.

Recent experience with Wilms' tumor: 1978-1991

BACKGROUND

The treatment of Wilms' tumor has undergone major advances in the past four decades. Current therapy is based on both the stage and pathology of the tumor. We have reviewed our recent experience with this tumor to assess the results of treatment on protocols that generally avoid the use of doxorubicin.

METHODS

Between January 1978 and December 1991 we treated 114 children with renal tumors. Ninety-one (80%) had favorable histology Wilms' tumor and 23 (20%), unfavorable histology tumors (13 anaplastic Wilms' tumors, four clear cell tumors of the kidney, and six sarcomatous tumors with rhabdoid elements). Chemotherapy was divided into two eras: 1978-1982 (vincristine and actinomycin-D) and 1983-1991 [vincristine and actinomycin-D for all patients, and cyclophosphamide for those with favorable histology and metastatic disease (n = 13) and all patients with anaplastic histology (n = 13)]. Four patients with clear cell or rhabdoid/sarcomatous tumor, three of whom are disease-free, were treated with a five-drug regimen (vincristine, doxorubin, cyclophosphamide, platinum, and VP-16). Approximately two thirds of the patients received megavoltage radiotherapy to the tumor bed. Mean abdominal radiation doses from 1978 to 1982 were slightly higher than those used from 1983 to 1991 (2,597 +/- 782 cGy vs. 2,039 +/- 524 cGy, respectively).

RESULTS

No isolated local failures were observed in any favorable histology patient who received radiotherapy. Among the 91 patients with favorable histology, there was no statistically significant difference in event-free survival irrespective of stage. Outcome for patients with anaplastic or clear cell variants was not different from that for those patients with favorable histology, but there were only small numbers in these groups for comparison. Only children with a rhabdoid/sarcomatous variant demonstrated survival that was different from all others (p = 0.00). Our previously reported patients with stage I tumors (< 550 g) (n = 11) who were treated by nephrectomy only continue to have an excellent outcome (survival 100%).

CONCLUSIONS

Wilms' tumors remain highly curable. Some unfavorable histology tumors require intensive therapy. Others such as our stage I tumors may be best observed without adjuvant therapy to avoid the toxicity of treatment.

Congenital sarcoma in the terminal ileum histologically resembling clear cell sarcoma of the kidney: a case report with an immunohistochemical study

We report a case of a newborn female with a rare tumor, a congenital sarcoma, presenting as an abdominal mass. Laparotomy demonstrated the tumor arising from the wall of the terminal ileum. Histologically, the tumor tissue was indistinguishable from clear cell sarcoma of the kidney and was composed of proliferating cells with poorly stained cytoplasm divided into nests or cords by arborizing vasculature. Immunohistochemical staining revealed that the neoplastic cells had a phenotype similar to metanephric blastemal cells of fetal kidney, ie, positive for vimentin and CD24 but negative for cytokeratin and CD9. The results suggest that this congenital tumor may originate from primitive mesenchymal cells phenotypically related to cells present in the fetal kidney.

Brain metastasis from clear cell sarcoma of the kidney--a case report and review of the literature

We describe a 5 year old boy with a 5.5 cm right frontal lobe brain metastasis from primary clear cell sarcoma of the kidney without evidence of tumor-associated edema or contrast enhancement on either computed tomography or magnetic resonance imaging. The metastasis regressed but did not disappear with chemotherapy and dexamethasone, and the residual tumor was removed surgically. On histological examination the majority of the tumor was composed of mature connective tissue with a rim of typical renal clear cell sarcoma cells at the brain-tumor interface. The avascular and desmoplastic nature of the metastasis may explain the unusual radiographic features. Brain metastases from this tumor have only infrequently been reported; therefore a brief review of this rare tumor is provided.

An immunohistochemical study comparing clear cell sarcoma of the kidney and Wilms' tumor

This study explores immunohistochemical characteristics that may be of diagnostic value in differentiating clear cell sarcoma of the kidney (CCSK) from Wilms' tumor (WT) and may provide some insight into the histogenesis of CCSK. Formalin-fixed, paraffin-embedded sections of 8 CCSK and 9 WT were stained, using the standard avidin-biotin peroxidase complex method, for vimentin (VIM), Factor-8 related antigen (F8A), epithelial membrane antigen (EMA), desmin (DES), S-100 protein and Mac 387. CCSK cells consistently exhibited moderate to strong diffuse cytoplasmic positivity for VIM and were negative for F8A, EMA, DES, S-100 and Mac 387. In contrast, only patchy groups of stromal cells and primitive glomeruloid structures in WT exhibited VIM-positivity. Blastemal cells were VIM-negative. Stromal cells with rhabdomyomatous differentiation exhibited cytoplasmic positivity for DES. Epithelial cells of maturing tubular structures showed EMA-positivity whereas immature tubular structures were EMA-negative. Neither blastemal, stromal nor epithelial elements in WT were positive for F8A, S-100 or Mac 387. Podocytes and mesangial cells of glomeruli in 3 mid-trimester human abortuses (controls) exhibited moderate to strong VIM-positivity. The importance of differentiating CCSK from WT has been repeatedly emphasized because of its poorer prognosis and the necessity of adding Adriamycin to the chemotherapeutic regime. The consistent VIM-positivity of CCSK cells can be a useful feature in differentiating it from "blastemal-predominant" WT, with which it is often confused. Although vimentin expression by CCSK cells is consistent with a mesenchymal character, the possibility of a histogenetic link with glomerular podocytes or mesangial cells should also be considered.

Clear cell sarcoma of kidney. Two cases in adults

BACKGROUND

Clear cell sarcoma of kidney (CCSK) is an aggressive renal tumor occurring most frequently in the second and third years of life. Although it has been reported in the literature in patients as old as 21 years of age, there has been no report focusing on adults with CCSK. The authors describe two cases of CCSK in men and the findings at autopsy.

METHODS AND RESULTS

Histologically, the renal tumors consisted of a homogeneous proliferation of polygonal or short spindle cells with faintly eosinophilic cytoplasm supported by a network of small vessels. Ultrastructurally, clusters of tumor cells were surrounded by collagen bundles. Elongated cytoplasmic processes, dilated rough endoplasmic reticulum, and intermediate filaments in the cytoplasm; primitive desmosome-like junctional structures; and incomplete basal lamina were observed. Immunohistochemically, tumor cells had positive results only for vimentin. Cytokeratins, epithelial membrane antigen, desmin, myoglobin, S-100 protein, neuron-specific enolase, and chromogranin A were not detected in the tumor cells. Both patients died within 2 years of onset of disease, and autopsy showed widespread metastases, especially in the soft tissue and bone.

CONCLUSIONS

Morphologic findings and an aggressive clinical course with metastasis to the bone and soft tissue are supportive of the diagnosis of CCSK in these patients.

Mesoblastic nephroma metastatic to the lungs and heart--another face of this peculiar lesion: case report and review of the literature

A case of mesoblastic nephroma in a 14-month-old girl who developed consecutive metastases in the lung and the heart is presented. This tumor is considered to be benign and cured by surgery only. Recurrent cases are extremely rare and usually related to unclear surgical margins. Metastatic mesoblastic nephroma has been previously described in only two cases. The present case highlights a new, previously undescribed feature--the ability to metastasize to sites other than lung.

Clear cell sarcoma of the kidney in a 4-month-old infant: a case report

A case of clear cell sarcoma of the kidney is described in a 4-month-old male infant. The tumor had a typical histological pattern, consisting of sheets of tumor cells possessing "empty" nuclei set within a delicate capillary network. There was extensive necrosis and tumor cell cytoplasm contained vimentin. This tumor occurs only rarely in infants less than six months of age. The different renal neoplasms of childhood have diverse prognoses and demand specific therapy so that accurate diagnosis is mandatory. The present case illustrates that clear cell sarcoma, a highly malignant neoplasm, must be considered in the differential diagnosis of a renal mass occurring in this age group.

Cytogenetic abnormalities in mesoblastic nephroma: a link to Wilms' tumour?

Cytogenetic analysis of tumour material from a congenital mesoblastic nephroma is reported. Two cell lines were found, one with a normal 46,XY karyotype and the other with a hyperdiploid 51,XY karyotype, including a rearrangement of chromosome 11 at 11p15. This finding is of interest since loss of allelic heterozygosity at polymorphic 11p15 loci has been described in sporadic Wilms' tumour [1], and both cytogenetic [2] and molecular [3] changes of 11p15 are found in the Wiedemann-Beckwith syndrome, a condition with a predisposition to embryonal tumours, particularly Wilms' tumour. Our results lead us to speculate on the implications relating to the pathogenesis of this relatively benign tumour variant with respect to the current understanding of the genetics of Wilms' tumour.

Malignant renal tumors of childhood

The prognosis in nephroblastoma (Wilms' tumor) has been improved considerably by treatment protocols combining surgery, chemotherapy, radiation therapy, and, in some clinical trials, pre-operative chemotherapy. Cure is now achieved in most patients. All clinical trials have employed treatment strategies tailored to the individual risk of the patient, including the histological subtype of the tumor. In the National Wilms' Tumor Study (NWTS) of the United States these subtypes have been divided into two groups of tumors according to their "favorable" or "unfavorable" histology. At the Kiel Pediatric Tumor Registry we have devised a system which distinguishes three groups of tumors classified according to prognosis. The first group includes tumors with a favorable prognosis, even if only surgery is performed. These comprise congenital mesoblastic nephroma (CMN) and cystic, partially differentiated nephroblastoma (CPDN). The second group consists of tumors posing an intermediate risk, such as typical nephroblastoma and its histological variants characterized by variations in the relative proportions of the histological components. Fetal rhabdomyomatous nephroblastoma (FRN) is also included in this group. The third group comprises tumors of high risk such as anaplastic nephroblastoma, clear cell sarcoma of the kidney (CCSK), and malignant rhabdoid tumor of the kidney (MRTK). Since histological diagnosis plays a crucial role in the assignment of a patient to a particular type of treatment protocol, knowledge of the histological appearance of the various tumor types both with and without preoperative treatment is of utmost importance.

Prognostic factors in nonmetastatic, favorable histology Wilms' tumor. Results of the Third National Wilms' Tumor Study

A comprehensive statistical analysis of relapses to lung and abdomen and of deaths due to tumor that occurred among 1466 patients with nonmetastatic, favorable histology (FH) Wilms' tumor entered on the Third National Wilms' Tumor Study (NWTS-3) was undertaken. In addition to lymph node involvement, age at diagnosis and tumor size as measured by the weight of the excised specimen were the most important determinants of outcome. The effects of tumor size were most apparent for patients with localized (Stage I) disease; age effects were found for patients with regional (Stage II or III) disease. The presence of microscopic tumor in the margin of surgical resection was an independent predictor of abdominal recurrence and death in the latter group. Although the report of the surgeon of diffuse soilage of the peritoneal cavity from tumor spilled or cut across in the course of nephrectomy was highly correlated with outcome, it was not possible to establish an independent prognostic role for such a finding after adjustment for the aforementioned factors. Patients with intralobar nephrogenic rests (ILNR) had a favorable survival outlook even after accounting for their generally younger ages and lower stages.

Cytologic characteristics of clear-cell sarcoma of the kidney (CCSK) in fine-needle aspiration biopsy (FNAB): a report of 4 cases

The cytologic findings observed in fine-needle aspiration biopsy (FNAB) of four cases of clear-cell sarcoma of the kidney (CCSK) are reported. Smears contained a monomorphic population of cells exhibiting non-descriptive cytoplasm and almost nude round to oval nuclei with smooth contour, evenly dispersed fine chromatin granules, and one or two small nucleoli. Some nuclei (approximately 40%) had a bar resulting from grooving or folding of the nuclear membrane. Comparison with smears of classical Wilms' tumor and malignant rhabdoid tumor allowed to recognize a distinctive pattern, different from other tumors of the kidney in infancy. The recognition of the CCSK cytologic pattern justifies the usage of aggressive preoperative chemotherapy protocols or the indication of surgery avoiding delays.

Primitive pelvic sarcoma resembling clear cell sarcoma of kidney

Clear cell sarcoma of kidney (CCSK) is an aggressive childhood renal tumor of unknown histogenesis that has not been reported to occur outside the kidney. The article describes an extrarenal neoplasm arising in the pelvic soft tissues of a 13-year-old boy that was composed predominantly of uniform mesenchymal cells with optically clear cytoplasm supported by an arborizing network of small blood vessels, which was indistinguishable in appearance from CCSK. The electron microscopic findings, although nonspecific, were essentially identical to those of CCSK, with tumor cells displaying fine chromatin, electron-lucent cytoplasm, and intercellular collagen but no evidence of tissue-specific differentiation. Immunocytochemical studies showed positivity for vimentin but negative results for desmin, myoglobin, cytokeratin, epithelial membrane antigen, S-100 protein, neuron-specific enolase and factor VIII-related antigen. Tumor cells were also nonreactive with Ulex lectin. This unusual pelvic tumor and CCSK may both derive from primitive mesenchymal cells and may represent phenotypic but not necessarily histogenetic analogs.

Nondifferentiated-type small cell sarcoma of kidney in a young woman

A case of rapidly fatal small cell sarcoma of kidney in a young woman is described. Histologic, immunohistochemical, and ultrastructural studies demonstrated some features not reported previously in the literature, such as the arrangement of vimentin intermediate filaments in small irregular masses and the presence of various types of cytoplasmic projections. These findings, together with the observation of rare neoplastic elements with immunophenotypic and subcellular aspects of histiocytic and myofibroblastic differentiation, suggest that this tumor should be included in a group of small cell sarcomas of kidney lacking features of differentiation and should be considered a new variant occurring in adulthood.

Congenital mesoblastic nephroma: possible prognostic and management value of assessing DNA content

The case records and pathology of all children with kidney tumours treated in the West Midlands Health Authority Region (WMHAR) from 1957 to 1986 were reviewed. The histology was reviewed by a panel of three paediatric pathologists. Thirteen (6%) out of 211 cases were considered to have congenital mesoblastic nephroma (CMN). Nine were of the conventional type, three of the atypical cellular type, and one mixed. DNA ploidy was investigated and showed two of the tumours to be aneuploid and nine diploid (tissue was not available in the two other cases). The two aneuploid tumours were of atypical cellular and mixed histology, respectively; the diploid tumours were of the conventional type in eight cases and atypical cellular in one. The atypical cellular type has been reported to behave more aggressively, but the benefit of additional treatment after surgery to prevent recurrence remains unclear. Measurement of DNA content by flow cytometry, together with histological subclassification, may be useful in selecting patients who will benefit from further treatment after surgery.

A case of adult mesoblastic nephroma: ultrastructure and discussion of histogenesis

A benign fibromyomatous kidney tumor with deep seated tubular structures in a 20-year-old woman is reported as a case of adult mesoblastic nephroma. Ultrastructural examination confirmed the fibromyomatous nature of the stroma and the tubules appeared to be an integral part of the tumor. The histogenetic relationship to congenital mesoblastic nephroma, Wilms tumor and other tumors is discussed. Radical nephrectomy was performed and the patient remained well 1 year later.

Cellular congenital mesoblastic nephroma: what are the options

Cellular congenital mesoblastic nephroma is a potentially aggressive variant of the usually benign congenital mesoblastic nephroma. Our recent experience with 3 patients with cellular congenital mesoblastic nephroma prompted a critical review of the literature to evaluate risk factors for recurrence and present treatment programs. A total of 38 patients, including our 3 patients, with cellular congenital mesoblastic nephroma were divided into 2 groups: those with recurrent (7) and those with nonrecurrent (31) tumors. A statistical comparison of clinical and pathological data was performed. Of the 7 patients with local recurrence and/or pulmonary metastasis, 3 died. The average time to first recurrence was 5.4 months. Histological differences were not predictive of recurrent disease. Pathologically positive surgical margins (p less than or equal to 0.02) were the only statistically significant variable suggesting recurrent disease. While the presenting age was not predictive of recurrence (p equals 0.27), the relative risk of recurrence doubles in the first 3 months of life and quadruples after 6 months of life. Treatment programs also were evaluated. An infant with cellular congenital mesoblastic nephroma, regardless of age, is cured with surgery alone given clear pathological margins. In 4 of 5 children with recurrent tumors Wilms tumor treatment agents (vincristine and actinomycin D) failed to control local or distant disease. Of these cases 2 subsequently were treated with sarcomatous chemotherapy (vincristine, cyclophosphamide and doxorubicin) and both are in remission. These agents may prove to be more efficacious in the treatment of local or metastatic disease.

Classical and cellular (atypical) congenital mesoblastic nephroma: a clinicopathologic, ultrastructural, immunohistochemical, and flow cytometric study

Sixteen cases of congenital mesoblastic nephroma (CMN) were studied. The tumors showed variable patterns of growth, degrees of cellularity, and mitotic activity. Six tumors had the classical pattern of CMN, seven were of the cellular or atypical variant and three showed combined features. The mean ages at presentation were 16 days, 5.3 months, and 2.3 months, respectively. Average size and weight were 5.1 cm and 94 g for classical CMN, 9.1 cm and 620 g for cellular CMN and 10.5 cm and 150 g for combined tumors. Cyst formation, hemorrhage and necrosis were confined to cellular CMNs and to cellular areas of combined CMNs. Mitotic activity ranged from 0 to 1/10 high-power fields (HPFs) in classical tumors to 25 to 30/10 HPFs in cellular tumors. Clear cell sarcoma-like areas were observed in three neoplasms. In ten cases there was invasion of perirenal fat; in one case each, invasion of the psoas muscle, renal vein wall, and renal vein lumen was observed. Ultrastructural and immunohistochemical studies showed features consistent with myofibroblastic differentiation. Flow cytometric analysis revealed euploidy in one classic CMN, one cellular CMN and in classic areas of a combined CMN; cellular areas of the latter tumor were aneuploid. All patients with follow-up were alive without evidence of disease after a mean period of 5 years following nephrectomy alone. No correlation was observed between the pathologic features assessed and the biologic behavior of these neoplasms.

Fine-needle aspiration biopsy of clear-cell sarcoma of the kidney: light and electron microscopic features

Smears from seven fine-needle aspiration biopsies from three patients with clear-cell sarcoma of the kidney were reviewed, and the findings were correlated with corresponding histopathologic appearances. In two cases, the tumor cells were polygonal to spindle-shaped and were loosely arranged in a matrix of mucoid material. The histopathologic examination of the resected tumors in these cases revealed a classic pattern. In the third case, the aspiration smears revealed round to polygonal cells with moderate to abundant cytoplasm but without the mucoid matrix. The predominant histologic appearance of this tumor was an epithelioid trabecular pattern. Electron microscopic findings were similar to those described in published studies.

Anaplastic Wilms' tumor and other clinically aggressive childhood renal neoplasms: ultrastructural and immunocytochemical features

The ultrastructural and immunocytochemical findings in a series of 32 rarely encountered childhood renal malignancies are reviewed. The discussion includes anaplastic Wilms' tumors, renal clear cell sarcomas, rhabdoid tumors, carcinomas, sarcomas, neuroendocrine tumors, and lymphomas. An attempt is made to assess the relative merits of these two techniques in the differential diagnosis of these often troublesome lesions.

Clear cell sarcoma of the kidney: report of a case with mandibular metastasis simulating a benign myxomatous tumor

The clear cell sarcoma of the kidney (CCSK) is one of the histologically unfavorable types of childhood renal tumors that has a propensity for osseous metastasis. We have presented the clinical and pathologic findings of the first well-documented case of a CCSK with mandibular metastasis, which was recognized approximately 18 months after the original diagnosis. Microscopically, the mandibular lesion had the features of a benign myxomatous neoplasm with the exception of occasional atypical spindle cells. Electron microscopic observation confirmed the undifferentiated nature of the neoplastic cells. It was concluded that the intensive chemotherapy that was administered to our patient very likely affected the histologic appearance of the mandibular metastasis as well as other recurrent lesions in the abdomen. Our review of the literature revealed only five previous examples of Wilms' tumor that had metastasized to the mandible. At least one of these earlier cases also represented a CCSK.

Congenital mesoblastic nephroma: a clinicoradiologic study of 17 cases representing the pathologic spectrum of the disease

Congenital mesoblastic nephroma (CMN) is a rare infantile renal tumor with a generally excellent prognosis. We describe 17 tumors that fit into the pathologic spectrum of CMN proposed by Beckwith, which ranges from benign renal tumors, through atypical "gray zone" lesions of more aggressive potential, to "crossover" tumors akin to clear cell sarcoma of kidney. Nine patients with histologically typical CMN were significantly younger and had smaller tumors than did eight patients with atypical CMN. Clinical features did not differ in the two groups of patients. A distinctive "ring sign" on renal sonography was commonly seen in patients with typical intrarenal CMN. All 17 patients were alive with no evidence of disease at a mean follow-up of 10 years. Nephrectomy was adequate therapy for younger infants and for those with typical CMN. Nephrectomy was probably also adequate therapy for infants 3 months of age or younger with atypical CMN, even if the tumor extended to the surgical resection margins and into the perinephric connective tissues. Adjuvant chemotherapy or radiation or both should be reserved for patients older than 3 months who have grossly unresected tumors and for those patients whose tumors have an unequivocally malignant histologic appearance or evidence of aggressive biologic behavior.