Clear cell sarcoma of the kidney: a clinicopathologic study of 21 patients with long-term follow-up evaluation

Overall survival nomogram and relapse-related factors of clear cell sarcoma of the kidney: A study based on published patients

Background

Rarity limits the breadth of study on clear cell sarcoma of the kidney (CCSK). There is currently no predictive model that quantifies the overall survival (OS) of CCSK and a few large sample-based analysis of relapse-related factors.

Methods

Patients were collected both from the Surveillance, Epidemiology, and End Results (SEER) database and case report articles extracted from the global online document database to form 2 groups. The first was the OS group, which was used to build and verify the nomogram for predicting the OS of CCSK. Independent predictors of OS were screened by Cox regression analysis to develop the nomogram. Nomogram accuracy was assessed by C-index, receiver operating characteristic (ROC), calibration, and decision curve analysis (DCA) curves. In addition, the difference in OS between receiving radiotherapy or not in stage I patients was analyzed by the Chi-square test. The second was the relapse group, which was used to analyze the relapse-related factors by Cox regression analysis and the Kaplan-Meier method with the log-rank test.

Result

256 patients were included in the OS group. The stage, chemotherapy, and radiotherapy were independent OS-related factors of CCSK, and the nomogram for predicting the OS of CCSK was established based on them. The results of the C-index, ROC, calibration, and DCA curves showed that the nomogram has good discrimination, accuracy, and clinical profitability. The Chi-squared test showed no significant difference in OS with receiving radiotherapy or not in stage I patients. The relapse group included 153 patients, of which 60 relapsed. The univariate Cox regression analysis showed no correlation between radiotherapy and relapse. The multivariate Cox regression analysis showed that stage and surgery/chemotherapy sequence were the independent factors for relapse. The log-rank test of seven chemotherapeutic drugs showed that etoposide (E), cyclophosphamide (C), vincristine (V), and doxorubicin (D) (all P < 0.05) had significant differences in preventing relapse, and then drew the relapse-free survival curves of these four drugs.

Conclusion

Our nomogram accurately quantified the OS of CCSK. There was no significant difference in OS between receiving radiotherapy or not in stage I patients. Stage, surgery/chemotherapy sequence, and the use of ECVD were relapse-related factors. Radiotherapy had no significant contribution to preventing relapse.

Childhood Clear Cell Sarcoma of Kidney: Incidence and Survival

This study is to describe current incidence of childhood clear cell sarcoma of kidney (CCSK) and to investigate the present survival of this cancer. Surveillance, Epidemiology, and End Result (SEER) data was used to identify children with CCSK and Wilms tumor (WT) aged 0-19 years in the US. Age-adjusted incidences were estimated over the decades. Age- and sex-specific epidemiology was also presented. Propensity score matching was used to balance features of CCSK and WT cases. Log rank test was used to compare survivals and Cox regression was used to evaluate independent effects of factors. The present age-adjusted incidence of childhood CCSK was 0.205 per million, which remained stable for years and ranked third in all pediatric renal tumors. The incidence rate ratios for boy and age under 4 were 3 and 21, respectively. The current 5-year overall survival (OS) rate for CCSK was 87%, which is not evidently inferior to that for WT (90%); however the outcome of CCSK was significantly poorer if both groups were well-balanced (OS rate was 86 vs. 95%). Early year of diagnosis and distant metastasis were independent survival factors. In conclusion, occurrence of CCSK remains stable over the years, with an age-adjusted incidence of 0.205 per million. Boy and age under 4 are risk factors for tumor development. CCSK currently has a favorable outcome but its nature may be more aggressive than common kidney tumor, which in turn proves efficacy of modern treatment.

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.

TLE1 Positive Clear Cell Sarcoma of the Kidney: A Case Report and Review of the Literature

Clear cell sarcoma of the kidney (CCSK) is an uncommon malignant tumor of uncertain histogenesis that occurs most commonly in childhood. Histologically, CCSK can mimic myxoid variant of synovial sarcoma (SS); however, the double positivity for CD99 and TLE1 in SS helps in excluding CCSK. Herein, we report a rare case of CCSK arising in the left kidney of a 3-year-old girl. The mass grossly measured 9.5 cm in maximum dimension and histologically showed the classic arborizing fibrovascular septae and background myxoid matrix that is usually seen in CCSK. The tumor however was double positive for CD99 and TLE1 which made it difficult to discriminate it from the myxoid variant of SS based on histopathological examination and immunophenotype alone, and genetic analysis for SYT gene rearrangement was required to reach a definitive diagnosis. Although there have been previous case reports of CCSK with positive expression of CD99 and negative TLE1, to our knowledge, this is the first case of CCSK expressing both CD99 and TLE1.

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.

Bladder Recurrence of Clear Cell Sarcoma of the Kidney Seven Years After Initial Presentation

Clear cell sarcoma of the kidney (CCSK) is the second most common pediatric renal malignancy after Wilms tumor. CCSK has the potential to metastasize to distant sites and was historically known as the bone metastasizing renal tumor. We report an exceedingly rare case of a bladder recurrence of CCSK. Our patient presented with gross hematuria 7 years after initial complete response. He was found to have a large sessile bladder tumor and underwent a partial cystectomy with right pelvic lymph node dissection. Final pathology was metastatic CCSK.

[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.

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 misdiagnosed as mesoblastic nephroma: a case report and review of the literature

Clear cell sarcoma of the kidney (CCSK) is a rare renal neoplasm of paediatrics, making up about 3% of all renal tumours in paediatrics, with a high tendency for developing bone metastasis. A seven year-old boy was referred to our clinic with two firm, large masses over the manubrium of the sternum and right frontal area, which pathologically were confirmed as a metastatic CCSK. The patient had a history of a renal mass three years earlier, for which radical nephrectomy had been performed, and histopathologic diagnosis was compatible with mesoblastic nephroma. Thus, no further investigation and therapy had been applied for the patient. CCSK is a rare but malignant and aggressive paediatric renal tumour, with a high tendency for developing distant bone metastases, leading to its poor prognosis. CCSK could be misdiagnosed as several other renal tumours such as mesoblastic nephroma, and thus CCSK should be taken carefully into consideration in the diagnosis of renal tumours.

Pediatric clear cell sarcoma of the kidney with atriocaval thrombus

Clear cell sarcoma of the kidney (CCSK) is an uncommon neoplasm that accounts for almost 3 % of pediatric renal tumors. Cavoatrial tumor thrombosis is very rare and because of poor response to chemotherapy, invasive surgical interventions such as open heart surgery may be indicated. A 6-year-old girl with CCSK of right kidney was treated with neoadjuvant chemotherapy. According to poor chemosensitivity, surgical intervention was planned. Right atriotomy was done, but intra-atrial part of tumor was very firm and unsuctionable; so the procedure was completed by laparotomy and en bloc resection of tumoral kidney and its cavoatrial extension through a limited venotomy on inferior vena cava. Although radical resection of CCSK with intracaval involvement should be considered as a multidisciplinary approach and intensive care and supports should be provided, atriocaval tumor in growth in CCSK is firm, non friable and non-adherent, and tumor en bloc resection may be possible through a limited venotomy via primary abdominal approach.

Clear cell sarcoma of the kidney: a review

Clear cell sarcoma of the kidney (CCSK) is a rare renal tumour that is observed most often in children under 3years of age. Only a few large series of CCSK have been reported and patients with CCSK are often included among patients with other types of childhood renal tumours. The purpose of this paper is to review the published series and case reports of CCSK and to create an up-to-date overview of clinical and histological features, genetics, treatment, and outcome.

Fetal and neonatal renal tumors

This is a review of renal tumors diagnosed between 1960 and 2007 in 47 fetuses and 163 infants less than 2 months old. There were 139 congenital mesoblastic nephromas, 41 Wilms' tumors, 23 rhabdoid tumors of the kidney, and 7 clear cell sarcomas of the kidney. The initial clinical manifestations, staging, management, and outcome of these patents are summarized in the tables and text.

Calvarial metastases as clinical presentation of renal cell carcinoma: report of two cases and review of the literature

Calvarium is a frequent target site of involvement for common neoplasms. Some cases of calvarial metastases have been reported in literature as secondary lesions from renal cell carcinoma (RCC), but only five cases have been described concerning calvarial mass as the first clinical presentation of this kind of tumor. In this report, we discuss the clinical aspects of two further cases we observed, in which the renal cell carcinoma was found thanks to the histological examination of a calvarial mass after surgery. We also briefly review the literature.

Fine-needle aspiration cytology of clear-cell sarcoma of the kidney: Study of eight cases

The largest series, to date, of fine-needle aspiration cytology (FNAC) findings in clear-cell sarcoma of the kidney (CCSK) is presented. All fine-needle aspirates of pediatric renal masses over a 17-yr period were reviewed. Eight out of 119 aspirates from late-stage childhood renal tumors (6.72%) were found to be CCSK. Ten aspirates from these eight patients and histopathological confirmation in six patients were available. Aspirates were cellular with three cell types: cord cells, septal cells, and small pyknotic cells. Cord cells, seen in all aspirates, were large polygonal cells with abundant eccentrically placed wispy cytoplasm, round to oval nuclei, and fine dusty chromatin. Occasional bare nuclei and frequent nuclear grooves were also seen. Small pyknotic cells were a degenerative change identified in 9 out of 10 aspirates. Stromal fragments with branching vascular cores were seen in 8 out of 10 aspirates, 6 of which had myxoid substance surrounding the vessel. Septal cells were spindle shaped and usually embedded in the stromal fragments. On the basis of cytology and histology, cases were classified into classical CCSK (5 cases), spindle-cell CCSK (1 case), and anaplastic CCSK (2 cases). Classical CCSK showed mostly cord cells with few stromal fragments. Spindle-cell CCSK showed preponderance of myxoid stromal fragments and septal cells. Anaplastic CCSK showed bizarre pleomorphic nuclei, coarse chromatin, and atypical mitosis. Cytology of CCSK is a spectrum with varying proportions of cord cells, septal cells, and mucopolysaccharide substance. Anaplastic CCSK is liable to misdiagnosis as Wilms tumor (WT) with unfavourable histology. Presence of eccentric cytoplasm in cord cells and nuclear grooves are the key to differentiation from Wilms tumor, including anaplastic variants.

Infrequent p53 gene mutations and lack of p53 protein expression in clear cell sarcoma of the kidney: immunohistochemical study and mutation analysis of p53 in renal tumors of unfavorable prognosis

A high prevalence of p53 gene mutation and protein expression has been found in the anaplastic variant of Wilms' tumor (WT), known to be associated with poor outcome. However, there are very few studies of p53 alterations in the other two rare and highly malignant renal tumors in childhood, in other words, clear cell sarcoma of the kidney (CCSK) and malignant rhabdoid tumor of the kidney (MRTK). Overexpression of p53 protein has been detected in eight CCSKs in one study, and in two in another, yet no molecular correlation with p53 gene mutations has been carried out. Our study is the first molecular analysis concerning p53 in CCSK. We investigated eight cases of CCSK and one case of MRTK for p53 protein expression by immunohistochemical staining. All were analyzed for p53 mutations in the region of exons 4 to 8 by polymerase chain reaction-single-strand conformational polymorphism (PCR-SSCP) method and DNA sequencing analysis. By histological study, no CCSK showed anaplastic features. None expressed p53 protein, but two harbored p53 mutations. One was in exon 5, with a base pair insertion between codons 162 to 163 causing frameshift alteration in amino acid. Another was a silent CTC-->CTT transversion in codon 289 of exon 8. The case of MRTK did not show any alterations of p53 protein or gene. Our result indicates that p53 alterations are infrequent in CCSK and do not seem to be primary genetic events in the pathogenesis of CCSK.

Surgical resection of calvarial metastases overlying dural sinuses

OBJECTIVE

Few reports have addressed the surgical management of cranial metastases that overlie or invade the dural venous sinuses. To examine the role of surgery in the treatment of dural sinus calvarial metastases, we reviewed retrospectively 13 patients who were treated with surgery at the University of Texas M.D. Anderson Cancer Center between 1993 and 1999. We compared them with 14 patients who had calvarial metastases that did not involve a venous sinus.

METHODS

Clinical charts, radiological studies, pathological findings, and operative reports were analyzed retrospectively.

RESULTS

The median age of patients with dural sinus calvarial metastases was 54 years. Nine patients were men and four were women. Renal cell carcinoma and sarcoma were the most common primary tumors. Similar features were noted in the 14 patients with nonsinus calvarial metastases. Of the 13 dural sinus calvarial metastases, 11 involved the superior sagittal sinus, and 2 involved the transverse sinus. In nine patients, the involved sinus was resected, and in four patients, the sinus was reconstituted after tumor removal. Nine patients in the dural sinus calvarial metastases group received en bloc resection, and four received piecemeal resection. No operative deaths occurred. The overall median actuarial survival was 16.5 months. The survival times of the two groups were comparable. In the group with dural sinus calvarial metastases, transient postoperative neurological deficits occurred in two patients (15%), and a permanent deficit occurred in one patient (8%). No patients in the group with nonsinus calvarial metastases experienced deficits after resection. Compared with piecemeal resection, en bloc resection was associated with significantly less blood loss.

CONCLUSION

Complete extirpation of calvarial metastases that overlie or invade a dural sinus can be achieved with only slightly more morbidity than complete removal of calvarial metastases that are located away from the sinuses. En bloc resection is as safe as piecemeal resection and is more effective in limiting operative blood loss. The overall recurrence and survival rates of patients with dural sinus calvarial metastases are similar to those of patients with calvarial metastases that do not involve the sinuses. Therefore, involvement of a dural venous sinus should not discourage resection of calvarial metastases. In carefully selected cancer patients, surgery provides effective palliation of symptomatic calvarial metastases that overlie or invade the venous sinuses.

Clear cell sarcoma of the pediatric kidney: detailed description and analysis of variant histologic patterns of a tumor with many faces

Clear cell sarcoma of the kidney is the most frequently misdiagnosed renal tumor in children. The majority of tumors present the classic histologic pattern, which allows a definitive diagnosis. However, there are unusual cases with lack of "clear" appearance of tumor cells, predominance or exclusive presence of variant histologic patterns, and presence of "neoplastic" appearing entrapped tubules. Furthermore, a small biopsy specimen may not show the classic histologic pattern. These tumors present a diagnostic challenge for the practicing pathologist who should be aware of the deviations from the classic histologic features in order to make a correct diagnosis.

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.

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.

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.

Implications of p53 protein expression in clear cell sarcoma of the kidney

Eight histologically-confirmed cases of clear cell sarcoma of the kidney (CCSK) were studied for possible mutations in the p53 tumor suppressor gene by the immunohistochemical demonstration of mutant p53 proteins using a monoclonal (DO7: Dako) and a polyclonal (AB565: Chemicon) antibody to p53 protein. All cases exhibited p53 protein nuclear immunopositivity, although in varying numbers of tumor cells and with different staining intensities. p53 protein (DO7 or AB565) was expressed in < 25% of the tumor cells in four (50%) of the cases, including the one case with a known long term survival of 13 years from the time of diagnosis. The other tumors showed p53 protein immunopositivity in > 25% of the tumor cells when stained with either DO7 or AB565 or both. The intensity of staining, graded on visual impression into weak, moderate or strong, did not correlate well with the ratio of positive staining tumor cells. While this study is unable to clarify the relative prevalence and importance of p53 mutational events in the pathogenesis of this aggressive renal tumor of childhood, it is reasonably suggestive that alterations in the p53 tumor suppressor gene do occur in CCSK.

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.

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.

Deletion of WT1 and WIT1 genes and loss of heterozygosity on chromosome 11p in Wilms tumors in Japan

Six of 39 sporadic Wilms tumors had gross homozygous or hemizygous WT1 and WIT1 deletions. Two Wilms tumor-aniridia-genitourinary abnormalities-mental retardation syndrome patients had total hemizygous WT1 and WIT1 deletions in both constitutional and nonsporadic type tumor cells. Four of the 8 tumors with WT1 and WIT1 deletions showed loss of constitutional heterozygosity (LOH) for markers limited to the 11p13 region. Seven of 19 Wilms tumors with neither WT1 nor WIT1 deletions also had LOH on 11p; 4 in the 11p15-11p13 region, one in the 11p15 and possibly also 11p13 regions, and two solely in the 11p15 region. Thus, 15 of the 41 Wilms tumors (37%) had WT1 and WIT1 deletions or LOH on 11p, and only 2 of the 27 tumors whose nonneoplastic normal tissues were available for study showed LOH limited to the 11p15 region. None of the 7 non-Wilms childhood renal tumors showed WT1 or WIT1 deletions, or LOH on 11p. These data suggest that Japanese Wilms tumors may be characterized by a higher incidence of the gross WT1 deletion and a lower incidence of LOH limited to the 11p15 region than the Caucasian counterparts. These molecular-genetic features may be contributing to the lower incidence of Wilms tumors in Japanese children than in Caucasian ones.

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.

Clear cell sarcoma of kidney: a clinicopathological study of eight cases from Malaysia

Eight cases of clear cell sarcoma of kidney were seen in the Department of Pathology, University Hospital, Kuala Lumpur, Malaysia over the 16-year period from 1973 to 1989. Five of the patients were males. Six patients were Malay, one Chinese and one Indian. The patients' ages ranged from 8 months to 3 years. Clear cell sarcoma was the original diagnosis in two patients while six were diagnosed as blastemal-predominant Wilms' tumours at presentation. Metastases developed in five patients. Metastatic sites included the thoracic vertebra, skull, orbit, humerus, radius, ulna, shoulder, lung and liver. The prolonged survival, of 9 years and 9 months, seen in one patient despite omission of Adriamycin (doxorubicin) from the chemotherapeutic protocol is highlighted. We also emphasise the histological factors which are of help in differentiating clear cell sarcoma from 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.

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.

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.

Unusual renal sarcoma in a young adult: its similarities to clear cell sarcoma of the kidney

We report an unusual case of renal sarcoma in a young adult. Histological examination demonstrated many similarities to the histopathological features of clear cell sarcoma of the kidney. Immunohistochemically, none of the intrinsic tumor cells showed positive staining with the antibodies against the intermediate filament proteins, epithelial membrane antigen, S100 protein, neuron-specific enolase, Leu-7 or myoglobin. The clinical course of this tumor was that of high grade malignancy, resulting in death with generalized metastases 13 months after tumor resection.

Ultrastructure and histogenesis of the renal tumors of childhood: an overview

This review discusses the ultrastructural and immunohistochemical features of the common childhood renal tumors, with an emphasis on their diagnostic usefulness. Speculations regarding their histogenesis also are presented, with the hope that these may serve to diminish some of the confusion surrounding the classification of these morphologically diverse lesions.