Renal neoplasms mimicking rhabdoid tumor of kidney. A report from the National Wilms' Tumor Study Pathology Center

Sarcomatoid and Rhabdoid Renal Cell Carcinoma: Clinical, Pathologic, and Molecular Genetic Features

Renal cell carcinoma (RCC) with sarcomatoid and rhabdoid morphologies has an aggressive biological behavior and a typically poor prognosis. The current 2022 WHO classification of renal tumors does not include them as distinct histologic entities but rather as transformational changes that may arise in a background of various distinct histologic types of RCC. The sarcomatoid component shows malignant spindle cells that may grow as intersecting fascicles, which is reminiscent of pleomorphic undifferentiated sarcoma. The rhabdoid cells are epithelioid cells with eccentrically located vesicular nuclei with prominent nucleoli and large intracytoplasmic eosinophilic inclusions. Studies have shown that RCCs with sarcomatoid and rhabdoid differentiation have distinctive molecular features. Sarcomatoid RCC harbors shared genomic alterations in carcinomatous and rhabdoid components, but also enrichment of specific genomic alterations in the sarcomatoid element, suggesting molecular pathways for development of sarcomatoid growth from a common clonal ancestor. Rhabdoid differentiation also arises through clonal evolution although less is known of specific genomic alterations in rhabdoid cells. Historically, treatment has lacked efficacy, although recently immunotherapy with PD-1/PD-L1/CTLA-4 inhibitors has produced significant clinical responses. Reporting of sarcomatoid and rhabdoid features in renal cell carcinoma is required by the College of American Pathologists and the International Collaboration on Cancer Reporting. This manuscript reviews the clinical, pathologic, and molecular features of sarcomatoid RCC and rhabdoid RCC with emphasis on the morphologic features of these tumors, significance of diagnostic recognition, the molecular mechanisms of tumorigenesis and differentiation along sarcomatoid and rhabdoid lines, and advances in treatment, particularly immunotherapy.

Malignant rhabdoid tumor arising in a mixed epithelial, stromal tumor of kidney: report of a male case, review of the literature

Mixed epithelial and stromal tumor (MEST) of the kidney is a rare biphasic tumor composed of both stromal and epithelial components, the latter showing a variable proportion of solid to cystic areas. These tumors show a marked female predominance, commonly occur in perimenopausal age groups, and often have an ovarian-type stroma with ER and PR positivity, suggesting steroids may play a role in pathogenesis. Although typically benign, rare cases showing malignant transformation have been reported. We present a case of a 42-year-old man with a 10 cm right kidney mass located in the renal pelvis. Histologically, the majority of the tumor was composed of a diffuse, sheet-like growth of malignant cells demonstrating a rhabdoid morphology with large nuclei, prominent nucleoli, and eosinophilic eccentric cytoplasm. Brisk mitotic activity and coagulative type necrosis was also noted. Intimately associated with this malignant rhabdoid component was a much smaller portion of tumor featuring variably sized bland epithelial tubules embedded within a stroma composed of bland spindle cells and areas of hyalinization, diagnostic of MEST. By immunohistochemistry, the malignant rhabdoid tumor portion of the neoplasm showed complete loss of nuclear INI-1, while the MEST component retained nuclear expression of this antigen. With these features taken together, our case represents a malignant rhabdoid tumor arising in a background of MEST. To our knowledge, this case represents the first case of a MEST showing malignant transformation in the form of malignant rhabdoid tumor in a male patient in the English language literature.

Updates in Histologic Grading of Urologic Neoplasms

CONTEXT.—

Tumor histology offers a composite view of the genetic, epigenetic, proteomic, and microenvironmental determinants of tumor biology. As a marker of tumor histology, histologic grading has persisted as a highly relevant factor in risk stratification and management of urologic neoplasms (ie, renal cell carcinoma, prostatic adenocarcinoma, and urothelial carcinoma). Ongoing research and consensus meetings have attempted to improve the accuracy, consistency, and biologic relevance of histologic grading, as well as provide guidance for many challenging scenarios.

OBJECTIVE.—

To review the most recent updates to the grading system of urologic neoplasms, including those in the 2016 4th edition of the World Health Organization (WHO) Bluebook, with emphasis on issues encountered in routine practice.

DATA SOURCES.—

Peer-reviewed publications and the 4th edition of the WHO Bluebook on the pathology and genetics of the urinary system and male genital organs.

CONCLUSIONS.—

This article summarizes the recently updated grading schemes for renal cell carcinoma, prostate adenocarcinomas, and bladder neoplasms of the genitourinary tract.

Malignant rhabdoid tumor in a solitary kidney arising in an adult patient with chronic obstructive renal calculi

INTRODUCTION

Malignant rhabdoid tumor (MRT) is one of the most aggressive and lethal malignancies in pediatric oncology, MRT of the kidney is an uncommon renal tumor in children and it's extremely rare in adult patients. With only seven previously reported adult cases in the English-literature, to our knowledge this is the first case that is associated with renal calculi.

PRESENTATION OF CASE

We present the case of a 65-year-old man with an MRT arising in a solitary kidney with multiple enlarged lymph nodes that compressing the inferior vena cava.

DISCUSSION

Malignant rhabdoid tumor of the kidney was originally described as a "rhabdomyosarcomatoid" variant of Wilm's tumor due to the resemblance of cells to rhabdomyoblasts, now this type of tumor is recognized as distant and unique malignant renal tumor. It affects usually children before the age of 2 years. Tumor tissue sampling is required to make the diagnosis of MRTK, based on either nephrectomy, core biopsy, or autopsy specimens. There is no established standard of care due to the paucity of cases. Surgery is considered to be the first choice of treatment if possible.

CONCLUSION

This case report reinforces the importance of recognizing this entity in the adult population, and discuss the possible treatment options of this rare and highly aggressive tumor.

Grading of renal cell carcinoma

Grading of renal cell carcinoma (RCC) has been recognised as a prognostic factor for almost 100 years. Numerous grading systems have been proposed, initially focusing upon a constellation of cytological features and more recently on nuclear morphology. It has been recommended that grading of RCC should be based upon nucleolar prominence/eosinophilia for grades 1-3, while grade 4 requires nuclear anaplasia (including tumour giant cells, sarcomatoid differentiation and/or rhabdoid morphology). The grading system was adopted formally by the International Society of Urological Pathology (ISUP) and subsequently by the World Health Organisation (WHO), being designated the WHO/ISUP grading classification in the fourth edition of the WHO classification tumours of the urinary system and male genital organs (2016). This grading system has been validated for both clear cell and papillary RCC. Validation studies for chromophobe RCC failed to demonstrate a correlation between grade and outcome for both the superseded Fuhrman grading system and the WHO/ISUP grading classification, and it has been recommended that these tumours not be graded. The WHO/ISUP system has been incorporated into the structured reports of the International Cancer Collaboration on Cancer Reporting for both clear cell and papillary RCC. It is also noted that other types of RCC may be graded, but it must be emphasised in the report that this is for descriptive and diagnostic purposes, and not outcome prediction. More recent studies have shown the incorporation of the presence of tumour necrosis into RCC grading to improve outcome prediction, and this has been validated in several studies.

SMARCB1-deficient Tumors of Childhood: A Practical Guide

The SMARCB1 gene ( INI1, BAF47) is a member of the SWItch/Sucrose Non-Fermentable (SWI/SNF) chromatin remodeling complex, involved in the epigenetic regulation of gene transcription. SMARCB1 acts as a tumor suppressor gene, and loss of function of both alleles gives rise to SMARCB1-deficient tumors. The prototypical SMARCB1-deficient tumor is the malignant rhabdoid tumor (MRT) which was first described in the kidney but also occurs in soft tissue, viscera, and the brain (where it is referred to as atypical teratoid rhabdoid tumor or AT/RT). These are overwhelmingly tumors of the very young, and most follow an aggressive and ultimately lethal course. Morphologically, most but not all contain a population of "rhabdoid" cells, which are large cells with abundant cytoplasm, perinuclear spherical inclusions, and eccentric vesicular nuclei with large inclusion-like nucleoli. MRT immunohistochemistry reveals complete loss of SMARCB1 nuclear expression, and molecular analysis confirms biallelic SMARCB1 inactivation in the vast majority. Rare AT/RTs have loss of SMARCA4, another SWI/SNF member, rather than SMARCB1. With the widespread adoption of SMARCB1 immunohistochemistry, an increasing number of SMARCB1-deficient tumors outside of the MRT-AT/RT spectrum have been described. In addition to MRT and AT/RT, pediatric tumors with complete loss of SMARCB1 expression include cribriform neuroepithelial tumor, renal medullary carcinoma, and epithelioid sarcoma. Tumors with variable loss of SMARCB1 expression include subsets of epithelioid malignant peripheral nerve sheath tumor, schwannomas arising in schwannomatosis, subsets of chordomas, myoepithelial carcinomas, and sinonasal carcinomas. Variable and reduced expression of SMARCB1 is characteristic of synovial sarcoma. In this review, the historical background, clinical characteristics, morphology, immunohistochemical features, and molecular genetics most germane to these tumors are summarized. In addition, familial occurrence of these tumors (the rhabdoid tumor predisposition syndrome) is discussed. It is hoped that this review may provide practical guidance to pathologists encountering tumors that have altered expression of SMARCB1.

Diagnostically Challenging Epithelioid Soft Tissue Tumors

In this article, we focus on the histologic features, differential diagnosis, and potential pitfalls in the diagnosis of epithelioid sarcoma, alveolar soft part sarcoma, clear-cell sarcoma, ossifying fibromyxoid tumor, and malignant extrarenal rhabdoid tumor. Numerous other soft tissue tumors also may have epithelioid variants or epithelioid features. Examples include epithelioid angiosarcoma, epithelioid malignant peripheral nerve sheath tumor, epithelioid gastrointestinal stromal tumor, and perivascular epithelioid cell tumor, among others.

Malignant rhabdoid tumor of the kidney arising in an adult patient

Malignant rhabdoid tumors (MRT) of the kidney are rare in children and even less common in adults, with only six previously reported adult cases. We present the case of a 60-year-old man with an MRT arising in the left kidney with extensive pulmonary micrometastases and thromboembolism resulting in thrombotic pulmonary microangiopathy (pulmonary tumor embolism syndrome). MRT is an extremely aggressive neoplasm with a short survival time.

Pure malignant rhabdoid tumor of the left kidney in an adult: A case report and review of the literature

Malignant rhabdoid tumors of the kidney (MRTKs) are extremely rare. Pure MRTKs in adult patients are particularly rare and have not been previously reported in China. Due to the non-specific clinical symptoms, it is difficult but also essential to be able to give a definite diagnosis. The present study reports a case of pure adult malignant rhabdoid tumor in a patient’s left kidney with characteristic clinicopathological features. Considering the fact that the characteristic findings are often not observed in clinical symptom and imaging studies, the histological features, immunohistochemical staining and cytogenetic studies may aid in confirming the diagnosis of pure MRTKs. Although pure adult MRTKs remain extremely uncommon, it is necessary to consider this possibility when such types of renal tumors are encountered.

PNET of kidney: Report of four cases

Primitive neuroectodermal tumor (PNET) of kidney is a rare tumor of kidney with only a few published reports. We report here four cases of PNET of kidney in the age group between 30 and 50 years who had complaints of vague pain and lump in loin. Hematuria was present in one case. Imaging of all cases revealed renal mass. The pathologic findings were consistent with PNET in all cases–confirmed by immunohistochemistry with diffuse membrane positivity of tumor cells of CD99. We could not do fluorescent in situ hybridization to demonstrate EWS-FLI-1 gene fusion. Each case was in the advanced stage. However, after giving postoperative radiotherapy and chemotherapy patients are still alive. Reporting of these cases are important as we got them in a short span of 3 years. In view of its poor prognosis, aggressive nature and different therapeutic approach– renal PNET should be differentiated from other small blue round cell tumors like neuroblastoma, rhabdoid tumor of kidney, nephroblastoma, small cell carcinoma, synovial sarcoma (monophasic, poorly differentiated) and non-Hodgkin lymphoma (NHL) by immunohistochemistry, cytogenetic, and molecular genetics study to see the different gene rearrangements in NHL and 3p deletion in small cell carcinoma.

INI1-deficient tumors: diagnostic features and molecular genetics

Significant progress has been made in understanding the molecular genetic alterations involved in sarcomagenesis. Cytogenetic and molecular studies have identified nonrandom genetic abnormalities, including tumor suppressor gene inactivation. Mutations, deletions, and other somatic alterations in the tumor suppressor gene INI1 (hSNF5; SMARCB1), which encodes a subunit of the SWI/SNF chromatin remodeling complex, were first described in the malignant rhabdoid tumor of infancy. Since then, INI1 has also been implicated in the pathogenesis of additional tumor types including renal medullary carcinomas and epithelioid sarcomas and a subset of epithelioid malignant peripheral nerve sheath tumors, myoepithelial carcinomas, and extraskeletal myxoid chondrosarcomas. As varied as this group appears, they all show loss of INI1 protein expression, a propensity for rhabdoid cytomorphology, and sometimes other overlapping immunohistochemical and histologic findings. We will review the clinicopathologic features of these tumor types and emphasize the clinical utility of INI1 immunohistochemistry in differential diagnosis.

Treatment of adult rhabdoid renal cell carcinoma with sorafenib

Renal cell carcinoma (RCC) with rhabdoid features is an uncommon and highly aggressive malignancy. We report a case of adult clear-cell RCC with extensive rhabdoid features treated with the tyrosine kinase inhibitor sorafenib. A review of the literature summarizes important aspects of this malignancy. We discuss clinical and histological findings as well as the patient's response to sorafenib therapy.

Adult renal cell carcinoma with rhabdoid morphology represents a neoplastic dedifferentiation analogous to sarcomatoid carcinoma

Renal cell carcinoma (RCC) with rhabdoid morphology (RCC-RM) is a recently described variant of RCC, which has an aggressive biologic behavior and poor prognosis, akin to sarcomatoid RCC. The current World Health Organization classification of RCC does not include the rhabdoid phenotype as a distinct histologic entity. The aim of this study is to investigate whether RCC-RM represents a dedifferentiation of a classifiable-type World Health Organization RCC or a carcinosarcoma with muscle differentiation. We reviewed 168 cases of RCC obtained between 2003 and 2008. From these cases, 10 (6%) were found to have areas of classic rhabdoid morphology. Immunohistochemistry for cytokeratin, epithelial membrane antigen, desmin, CD10, and CD117 was performed in each case using the labeled streptavidin-biotin method. Rhabdoid differentiation was identified in association with conventional-type RCC (9) and with unclassifiable-type RCC with spindle cell morphology (1). In all cases, both the rhabdoid and nonrhabdoid tumoral areas were positive for cytokeratin and epithelial membrane antigen and negative for desmin. Cytokeratin positivity in the rhabdoid areas was focal. In cases associated with conventional-type RCC, CD10 was positive in both the rhabdoid and nonrhabdoid foci. CD117 was negative in these tumors. The unclassifiable-type RCC with spindle cell morphology was negative for both CD10 and CD117. The similar immunophenotype between the rhabdoid and nonrhabdoid tumoral foci supports the origin of the rhabdoid cells from the classifiable-type RCC. Areas of rhabdoid morphology do not represent muscle metaplastic differentiation. Renal cell carcinoma with rhabdoid morphology may represent a dedifferentiation of a classifiable-type RCC, similar to that of sarcomatoid differentiation. The recognition of RCC-RM is important as it allows for the inclusion of these high-grade malignancies into a category associated with poor prognosis despite lacking the spindle cell component classically identified as sarcomatoid change.

Age, stage, and radiotherapy, but not primary tumor site, affects the outcome of patients with malignant rhabdoid tumors

BACKGROUND

Malignant rhabdoid tumors (MRTs) are aggressive and often fatal; the Surveillance, Epidemiology, and End Results (SEER) database offers an opportunity to study this rare malignancy.

METHODS

From the SEER database, we extracted records of patients with a reported diagnosis of MRT and analyzed them for clinical features and survival rates by univariate and multivariate analyses.

RESULTS

For the 229 patients included in our data, who were diagnosed from 1986 to 2005, primary tumors were located in the central nervous system (CNS) (35%), kidneys (20%), and extra-renal non-cranial sites (ERNC-MRTs) (45%). Most patients with renal and CNS tumors were less than 18 years old (87% and 96%, respectively) while more than half of the patients with ERNC-MRTs (61%) were adults. Among staged tumors, 23% were localized, 34% regional, and 43% distant. Renal tumors had significantly more metastatic disease (47%; P = 0.006) than ERNC-MRTs. The estimated 5-year survival for the entire group was 33 +/- 3.4% (SE). Univariate and multivariate analyses showed that age at diagnosis (2-18 years), localized stage of tumors, and use of radiotherapy were significantly associated with improved survival. Adults had a better outcome than young children (<2 years old) but a poorer outcome than older children (2-18 years old); tumor stage, but not radiotherapy use, affected outcome in adults. The survival and prognostic factors of children diagnosed before and after 2000 did not differ significantly.

CONCLUSION

Our population-based study indicates that age at diagnosis, tumor stage, and use of radiotherapy favorably impact survival rates of patients with MRTs.

Molecular Pathology of the Genitourinary Tract: Molecular Pathology of Kidney and Testes

With the advent of newer molecular technologies, our knowledge of cellular mechanisms with tumors of the kidney and testis has grown exponentially. Molecular technologies have led to better understanding of interplay between the von Hippel-Lindau gene and angiogenic cytokines in renal cancer and isochromosome 12p in testicular neoplasms. The result has been development of antiangiogenic-targeted therapy within recent years that has become the mainstay treatment for metastatic renal cell cancer. In the near future, classification and diagnosis of renal and testicular tumors through morphologic analysis will be supplemented by molecular information correlating to prognosis and targeted therapy. This article outlines tumor molecular pathology of the kidney and testis encompassing current genomic, epigenomic, and proteonomic findings.

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.

Imaging accuracy and incidence of Wilms' and non-Wilms' renal tumors in children

PURPOSE

The purpose of this study is to determine the actual incidence, age distribution, and preoperative imaging accuracy of non-Wilms' tumors (nWT) in children with renal masses.

METHODS

Pathologic reports from all tumor nephrectomies or open renal biopsies performed at a single institution from September 1999 to June 2005 were analyzed. Patient demographics, pathologic findings, specific imaging study descriptors, and differential diagnoses were tabulated. Accuracy of imaging studies in identifying specific tumors was calculated.

RESULTS

Ninety-two patients were identified. Sixty-eight had Wilms' tumor (WT) and 24 had an nWT. The nWT group included congenital mesoblastic nephroma (5), clear cell sarcoma (4), neuroblastoma (4), renal cell carcinoma (4), lymphoma (2), angiomyolipoma (2), teratoma (1), hemangioma (1), and renal epithelial tumor (1). When grouped by ages, the incidence of nWT was between 0% and 83%. Sensitivity, specificity, positive predictive value, and negative predictive value for computed tomography (CT) determining a diagnosis of WT were 0.92, 0.55, 0.84, and 0.73, respectively. The CT reports explicitly stated a potential diagnosis in 89% of cases, with a diagnostic accuracy of 82%.

CONCLUSIONS

Non-Wilms' tumors may represent a significant proportion of renal tumors in children, especially in children aged less than 6 months or greater than 12 years. Preoperative imaging is of limited value in differentiating these tumors. These data have significant implications for parental counseling, surgical plan, and the choice of neoadjuvant chemotherapy and argue in favor of obtaining a tissue diagnosis before instituting therapy.

Primitive neuroectodermal tumor of the kidney: a single institute series of 16 patients

OBJECTIVES

Primitive neuroectodermal tumor (PNET) of the kidney is a rare entity, the diagnosis usually being made at histopathology. Few cases reported in literature revealed a variable presentation and an aggressive behavior. The purpose of our study was to review our experience in diagnosis and the management of patients with renal PNET.

METHODS

The records of 16 patients of renal PNET treated between 1995 and 2003 were reviewed retrospectively and our data compared with the literature.

RESULTS

There were 10 male and 6 female patients with median age of 27 years. At presentation, 10 patients (63%) had localized disease, 5 (31%) had metastatic disease and 1 (6%) had locally advanced disease. The presence of Homer-Wright type rosettes on hematoxylin and eosin staining and CD99 (cluster differentiation) products positivity on immunohistochemistry supported the diagnosis. Radical nephrectomy was performed in operable cases and all patients received chemotherapy. Nine patients received adjuvant radiotherapy to the renal bed. Median follow-up was 31 months (range 4 to 92). Overall median survival was 40 months with 3- and 5-year survival of 60% and 42%, respectively.

CONCLUSIONS

The diagnosis of renal PNET must be considered in young patients presenting with renal mass. Standard therapy consists of combination of surgical resection, postoperative irradiation and chemotherapy. Chemotherapy regimen used is either RCT II (round cell tumor) protocol or EFT 2001 (Ewing's family of tumors) protocol. However, further studies are required to validate the appropriate chemotherapy protocol.

Part I: Primary malignant non-Wilms' renal tumours in children

Non-Wilms' tumours form a small heterogeneous group of clinically significant renal malignancies in children, including renal-cell carcinoma, clear-cell sarcoma, (congenital) mesoblastic nephroma, rhabdoid tumour, and renal medullary carcinoma. Good progress has been made in the assessment of these tumours, which has led to a greater understanding of the molecular changes that occur in their development. This review is the first of two parts, and provides an updated review of the clinical presentation, imaging, and pathology of these tumours.

Renal cell carcinoma with rhabdoid features: an aggressive neoplasm with overexpression of p53

CONTEXT

Adult renal cell carcinoma (RCC) with rhabdoid features is a recently recognized morphologic variant of kidney carcinoma. To date, only very few studies have been published on this subject and p53 was not previously studied.

OBJECTIVE

To evaluate clinical attributes, morphology, and immunohistochemistry in RCC with rhabdoid component.

DESIGN

Reviewing a consecutive series of 310 RCCs, we identified 14 cases of RCC with rhabdoid features. All cases were reviewed and subjected to detailed clinical and pathologic studies with immunohistochemical evaluation of p53.

RESULTS

All tumors were clear RCCs with rhabdoid component representing from 5% to 50% of the tumor volume. Rhabdoid cells were large with a central eosinophilic intracytoplasmic inclusion and an eccentric atypical nucleus. Tumor necrosis was common (13/14) and sometimes extensive. Nine of 14 tumors were staged pT3, 4 of 14 were pT2, and only 1 tumor was pT1. On immunohistochemistry, rhabdoid cells were positive for vimentin (14/ 14), epithelial membrane antigen (11/14), and cytokeratin (9/14). Desmin and smooth muscle actin were always negative. p53 was positive in 10 of 14 tumors in the rhabdoid areas (5%-50% of tumor cells stained) but only in 5 of 14 cases in usual clear renal cell areas. In the follow-up, 10 of 14 patients developed metastases and 6 of 14 died of the disease. The median of survival was 8 months.

CONCLUSIONS

We showed that RCC with rhabdoid features is a very aggressive neoplasm with a poor prognosis. We observed an overexpression of p53 in the rhabdoid component that may be implicated in the tumor dedifferentiation.

Classification of malignant pediatric renal tumors by gene expression

BACKGROUND

The most common malignant renal tumors of childhood are Wilms tumor (WT), clear cell sarcoma of the kidney (CCSK), cellular mesoblastic nephroma (CMN), and rhabdoid tumor of the kidney (RTK). Because these tumors present significant diagnostic difficulties, the goal was to define diagnostically useful signatures based on gene expression.

PROCEDURES

Gene expression analysis using oligonucleotide arrays was performed on a training set of 47 tumors (10 CCSKs, 9 CMNs, 8 RTKs, and 20 WTs). Classifiers were developed for each tumor type using variations of compound covariate class predictor. The classifiers were applied to an independent test set of 72 tumors (3 CMN, 7 CCSK, 4 RTK, and 58 WT). Central review diagnosis was utilized as the gold standard. Correlation with the institutional diagnosis and qualitative estimation of confidence levels at the time of central review were noted.

RESULTS

Within the training set, classifiers resulted in no errors when >10 genes were utilized. Top genes in each classifier were verified using quantitative reverse transcription-polymerase chain reaction (RT-PCR). Applying the classifiers to the test set, 71 of 72 tumors were correctly classified with a confidence level of >99%. The exception was incorrectly classified by the gold standard. In comparison, by histopathology 31% of the non-WT were not accurately classified by the local institution, and 29% were classified with <95% confidence on central review.

CONCLUSIONS

Classifiers based on gene expression provide diagnostic confidence and accuracy greater than that of pathologic analysis alone. Tumors that show ambiguous gene expression profiles are those that are also pathologically and molecularly ambiguous and merit further analysis.

Esophageal carcinoma with a rhabdoid phenotype: a case report of diagnosis by endoscopic ultrasound-guided fine-needle aspiration

Malignant extra renal tumors with rhabdoid phenotype are aggressive neoplasms associated with a poor prognosis. These tumors have been reported in soft tissue and various organs including the gastrointestinal tract. We report one of such tumors arising in the esophagus and discuss the cytopathologic, immunohistochemical, and ultrastructural features. Endoscopic ultrasound-guided fine-needle aspiration (FNA) cytology revealed a highly cellular tumor, consisting of polygonal poorly cohesive cells with prominent eosinophilic paranuclear cytoplasmic inclusions. Immunohistochemical staining showed strong cytoplasmic positivity for vimentin and cytokeratin. Electron microscopy revealed presence of numerous intermediate filaments. To the best of our knowledge, this is the first example of carcinoma with rhabdoid phenotype of the esophagus diagnosed by FNA cytology.

Atypical teratoid rhabdoid tumors of childhood: diagnosis, treatment and challenges

Atypical teratoid rhabdoid tumor of the brain was described as a unique entity in the late 1980s. It occurs primarily in early childhood but the true incidence of the disease is not yet known. At presentation, the differential diagnosis includes medulloblastoma, primitive neuroectodermal tumor, ependymoma and choroid plexus carcinoma. Atypical teratoid rhabdoid tumor behaves in a very aggressive manner and while cure is possible for a small minority of patients, no standard or effective therapy has been defined for most patients. Since its first description, considerable pathologic, cytogenetic and molecular characterizations, as described in this review, have been accomplished that provide insight into the possible molecular etiology of the disease and of malignant rhabdoid tumors that occur outside the CNS. Co-operative group clinical trials that focus solely on atypical teratoid rhabdoid tumor are needed that incorporate biologic studies along with evaluations of aggressive treatment approaches. The goal of these trials should be to increase the cure rate for children with atypical teratoid rhabdoid tumor and further increase our understanding not only of atypical teratoid rhabdoid tumor, but also of other pediatric brain tumors.

Urothelial carcinoma with rhabdoid features: report of 6 cases

Extrarenal rhabdoid tumors have been described in a variety of primary sites with only rare case reports of urothelial carcinomas with rhabdoid features in the literature. In this report, we describe the clinicopathologic characteristics, including clinical follow-up on 6 cases of urothelial carcinoma with prominent rhabdoid features. Four cases were retrieved from the consultation files of one of the authors and 2 were retrieved from the surgical pathology files at our institution. The patients were all men, with ages ranging from 53 to 86 years (mean, 66.5 years). Patients initially presented with hematuria or obstructive symptoms. The sites included bladder (n = 4) and renal pelvis (n = 2). All cases had a prominent rhabdoid component (mean, 60%), ranging from 40% to 80%. In addition to the rhabdoid component, multiple coexistent histological components were seen, including in situ urothelial carcinoma (carcinoma in situ) and high-grade papillary urothelial carcinoma (n = 2), poorly differentiated carcinoma with small-cell features (n = 1), sarcomatoid (n = 2), and a myxoid component (n = 2). All cases in this series had focal or diffuse positive staining with one or more cytokeratin markers (epithelial membrane antigen, CAM 5.2, AE1/AE3). Of the 6 patients, 4 were treated initially with surgery (radical cystoprostatectomy, n = 2; radical nephrectomy, n = 2). Of 6 patients, 2 died within 1 month, whereas a third patient died within 4 months. The remaining 3 patients were alive at 3, 3, and 9 months after diagnosis. The histological and immunohistochemical findings in this study serve to broaden the morphological spectrum of urothelial carcinomas with prominent rhabdoid features and add further evidence as to their poor prognosis.

The spectrum of pediatric tumors in infancy, childhood, and adolescence: a comprehensive review with emphasis on special techniques in diagnosis

The spectrum of pediatric tumors varies considerably, from those derived from blastemal cells in various organ systems to proliferations of soft tissue supporting cells to hamartomatous processes that mimic malignant tumors. Small round cell tumors are often undifferentiated or poorly differentiated, making it difficult sometimes to provide a definitive diagnosis. Both benign and malignant tumors require a coordinated method for diagnosis, and need a comprehensive evaluation to provide the most appropriate diagnosis for designing therapy and predicting prognosis. Pediatric tumors require the integration of routine histopathologic examination with histochemical, immunocytochemical, ultrastructural, cytogenetic, and diagnostic molecular pathology techniques. This review provides updated guidelines with respect to the application of these special techniques in this rapidly evolving diagnostic arena.

Inherited Susceptibility for Pediatric Cancer

The percentage of childhood cancers that are caused by a clearly inherited predisposition varies significantly from only a few percent to more than 50% with individual tumor types. Recent advances in genetic testing and studies of cohorts of cancer patients have demonstrated the likelihood of identifying a cancer susceptibility mutation for numerous childhood cancers. Inherited predisposition to cancer is frequently the result of dominant constitutional mutations in tumor suppressor genes, which can be inherited from an affected parent or occur de novo during gametogenesis. In this article, we review the childhood malignancies that are associated with at least a 10% likelihood of being caused by a genetic susceptibility to cancer and therefore warrant consideration for a genetic evaluation; these malignancies include retinoblastoma, adrenocortical carcinoma, atypical teratoid and malignant rhabdoid tumors, optic pathway tumors, juvenile myelomonocytic leukemia, malignant peripheral nerve sheath tumors, vestibular schwannomas, endolymphatic sac tumors, hemangioblastomas, medullary thyroid cancer, pheochromocytomas, and paragangliomas. Children with other malignancies may also warrant genetic evaluation if there is the co-occurrence of malignancy and two or more congenital anomalies, or malignancy and a significant family history of related cancers. We also review the importance of the correct genetic diagnosis in order to ensure appropriate treatment and ongoing cancer surveillance for the child with cancer and closely related family members (e.g., parents and siblings).

Clear cell renal cell carcinoma

Clear cell RCC is the most common type of RCC that occurs in adults. It has the worst prognosis among the common epithelial tumors of the kidney. Histologically, a wide range of morphologic patterns can be encountered. Those cases with a multi-locular cystic architecture are considered to be a distinct subtype because of the clinicopathologic features.

Cytopathology of uncommon malignant renal neoplasms in the pediatric age group

Malignant renal neoplasms are common solid tumors in pediatric oncology practice. These include the common Wilms' tumor/nephroblastoma and the uncommon neoplasms such as clear-cell sarcoma of the kidney (CCSK), rhabdoid tumor, renal-cell carcinoma, and others. The aim of this study was to describe in detail the cytopathological features of the histopathologically proven uncommon pediatric renal tumors. Aspirates from Wilms' tumor, which are mesenchyme predominant, show clusters of spindle cells associated with the matrix material. Evidence of rhabdomyoblastic differentiation may be present. CCSK, classic subtype, is characterized by round to oval cells arranged perivascularly and also in sheets and clusters intimately associated with a metachromatic matrix mucopolysaccharide material better appreciated in May-Grunwald-Giemsa (MGG)-stained smears. The cells also have more abundant cytoplasm and may show nuclear grooves. Spindle-cell pattern of CCSK is difficult to diagnose on aspiration cytology. Renal-cell carcinoma of childhood shows similar cytological features as its adult counterpart. Rhabdoid tumor of the kidney is characterized by a monomorphic population of cells with abundant cytoplasm, eccentric nuclei with prominent nucleoli. Intrarenal yolk sac tumor is a rare neoplasm and shows severely pleomorphic cells on aspiration. Awareness of these entities is important for the practicing cytopathologist. Further, non-Wilms' renal malignant neoplasms must be distinguished from the common Wilms' tumor so that appropriate chemotherapy protocols may be instituted in cases where the tumor is in an advanced stage of malignancy.

Collecting duct carcinoma exhibiting diastase-resistant PAS-positive globular cytoplasmic inclusions and rhabdoid features arising in adult polycystic kidney disease: a case report

A 76-year-old man complained of lumbago, and a subsequent detailed examination revealed a mass in the left kidney. Macroscopically, multiple cysts were recognized in the bilateral kidney; the tumor proliferated predominantly in the renal medulla and showed a whitish color with focal necrosis and hemorrhage. A histologic examination of the surgically resected tumor showed various growth patterns, such as solid, tubular, and papillary, by tumor cells. The diagnosis of collecting duct carcinoma (CDC) was made. Furthermore, tumor cells contained globular inclusions resembling hyaline globules and large eosinophilic inclusions, resulting in rhabdoid features, in the cytoplasm. Histochemically, globular inclusions were positive for periodic acid-Schiff (PAS) with diastase pretreatment. Immunohistochemically, large esosinophilic inclusions were reactive for vimentin. Although these findings are rare in CDCs, they should be recognized in the pathologic spectrum of CDCs. Int J Surg Pathol 12(2):171-177, 2004

Synovial Sarcoma of the Kidney With Rhabdoid Features

We report 3 cases of synovial sarcoma with rhabdoid features, initially diagnosed as adult rhabdoid tumors. Two women (case nos. 1 and 2, 35 years and 27 years of age, respectively) and one man (case no. 3, 26 years of age) presented to their physicians with right flank pain. On physical examination, a poorly defined, firm, palpable mass was found in the upper right quadrant of the abdomen in all cases. Sonography and computed tomography revealed solid, cystic masses in the right kidneys that ranged in size from 8.5 to 20.0 cm. Right radical nephrectomies were performed in all patients. One patient died of disease, and the other two patients were alive and disease-free after chemotherapy and radiotherapy. Microscopic examination revealed that the tumors were composed mostly of rhabdoid cells with eccentrically located nuclei, prominent nucleoli, and eosinophilic cytoplasm. We also found areas of fasciculated spindle cells, sharply separated from or irregularly admixed with areas of rhabdoid cells. There was tumor necrosis, but no epithelial areas were seen. Hemangiopericytic vasculature was at least focally observed in all cases. The tumor cells were positive for CD99 and bcl-2 in all cases and for CD56 in two cases and negative for CD34 and smooth muscle actin in all cases. The cells in case no. 1 were focally positive for cytokeratin. To verify the possibility of synovial sarcoma with rhabdoid features, reverse transcriptase polymerase chain reaction using RNA extracted from frozen tissue in case no. 1 and formalin-fixed, paraffin-embedded tissue in case nos. 2 and 3 was performed. SYT-SSX2 transcripts were detected in all 3 cases. These cases indicate that synovial sarcoma of the kidney should be considered in the differential diagnosis of mesenchymal kidney tumors with prominent rhabdoid features. A subset of adult rhabdoid tumors may be a rhabdoid variant of synovial sarcoma, and molecular studies to detect SYT-SSX fusion transcripts are recommended for an accurate diagnosis.

Primitive Neuroectodermal Tumor (PNET) of the kidney: a case report

Background

A case of Primitive Neuroectodermal Tumor (PNET) of the kidney in a 27-year-old woman is presented. Few cases are reported in the literature with a variable, nonspecific presentation and an aggressive behaviour. In our case, a radical nephrectomy with lymphadenectomy was performed and there was no residual or recurrent tumour at 24-month follow-up.

Methods

The surgical specimens were formalin-fixed and paraffin embedded. The sections were stained with routinary H&E. Immunohistochemistry was performed.

Results

The immunohistochemical evaluation revealed a diffuse CD99 positivity in the cytoplasm of the neoplastic cells. Pankeratin, cytokeratin AE1/AE3, vimentin, desmin, S100, cromogranin were negative. The clinical presentation and the macroscopic aspect, together with the histological pattern, the cytological characteristic and the cellular immunophenotype addressed the diagnosis towards primary PNET of kidney.

Conclusions

Since sometimes it is difficult to discriminate between PNET and Ewing's tumour, we reviewed the difficulties in differential diagnosis. These tumors have a common precursor but the stage of differentiation in which it is blocked is probably different. This could also explain their different biological behaviour and prognosis.

Recent advances in pediatric renal neoplasia

Over the past 6 years, molecular genetic studies have significantly advanced our understanding of pediatric renal neoplasms. The cellular variant of congenital mesoblastic nephroma (but not the classic variant) has been shown to bear the same t(12;15)(p13;q25) and ETV6-NTRK3 gene fusion as infantile fibrosarcoma, a tumor with which it shares morphologic and clinical features. Rhabdoid tumor of the kidney is characterized by deletion of the hSNF5/INI1 gene, which links it to other rhabdoid tumors of infancy that arise in the soft tissue and brain. Primary renal synovial sarcomas and renal primitive neuroectodermal tumors have become accepted entities, and likely comprise a subset of what had previously been termed "adult Wilms tumor." Renal carcinomas associated with Xp11.2 translocations that result in fusions involving the TFE3 transcription factor gene have been delineated, including a distinctive neoplasm that shares the identical gene fusion as alveolar soft part sarcoma. Most recently, a distinctive type of renal neoplasm with a t(6;11)(p21;q12) has been described, and the cloning of the resulting gene fusion links it to the Xp11 translocation carcinomas. Together, these last two translocation-associated tumors represent a significant proportion of pediatric renal cell carcinomas. This review highlights each of these recent advances.

Neuroblastoma mimicking rhabdoid tumor of the kidney

Rhabdoid tumor of the kidney (RTK) has mimicked other renal tumors histologically, but there has been only one previous report of neuroblastoma mimicking RTK. The authors present the case of a 17-month-old boy who presented with a large left renal mass that was diagnosed as RTK. At the completion of therapy he was found to have residual masses. They were biopsied and found to be viable neuroblastoma.

Comparative genomic hybridization and pathological findings in atypical teratoid/rhabdoid tumour of the central nervous system

The atypical teratoid/rhabdoid tumour (AT/RT) is an uncommon tumour of the central nervous system in children, characterized by the presence of a rhabdoid cell component associated with variable combinations of primitive neuroectodermal tumour, mesenchymal and epithelial differentiation. Immunohistochemistry reveals a complex pattern of antigen expression and cytogenetic studies have demonstrated losses from chromosome 22. We have performed comparative genomic hybridization (CGH) on paraffin-embedded material from three cases of AT/RT. Two cases showed losses from chromosome 22 associated with other chromosome imbalances including losses from 1p in both cases. The third case demonstrated a loss from 8p as the sole abnormality. While monosomy or deletion from chromosome 22 is a useful diagnostic marker for AT/RT, it is not present in all cases. The variation in cytogenetic patterns reported for this tumour type raises the possibility that different genetic pathways may underlie this tumour phenotype and warrants the further definition of the cytogenetic spectrum for this rare tumour.

Renal cell carcinoma with rhabdoid features: an aggressive neoplasm

AIMS

Only a few reports on renal cell carcinoma with rhabdoid features have been published. This study was performed to investigate the clinicopathological characteristics of renal cell carcinomas with rhabdoid features.

METHODS AND RESULTS

Among 253 cases of renal cell carcinoma in adults, eight cases with rhabdoid features were detected. Rhabdoid areas ranged from 10% to 90% of each of the cases. Seven of the eight cases were TNM stage III or IV, and four of the eight cases died within 8 months of surgery. Immunohistochemically, the rhabdoid areas were positive for CAM 5.2 (4/8), AE1/AE3 (6/8), epithelial membrane antigen (6/8) and vimentin (8/8), and negative for myogenetic markers (0/8). The mean MIB-1 labelling index in the rhabdoid areas was higher than that in the definite carcinomatous areas. Ultrastructurally, perinuclear whorls of intermediate filaments were demonstrated in three of the eight cases using paraffin-embedded blocks.

CONCLUSIONS

The rhabdoid areas in renal cell carcinoma have histological, immunohistochemical and ultrastructural similarities to malignant rhabdoid tumours. Renal cell carcinoma with rhabdoid features is a highly aggressive neoplasm and its malignant behaviour may be due to the high cell-proliferative activity of the rhabdoid areas. Rhabdoid features in renal cell carcinoma may represent the endpoint of clonal evolution of renal cell carcinoma (especially in clear cell type cases).

Adult rhabdoid renal cell carcinoma

BACKGROUND

Pediatric rhabdoid tumor of the kidney is regarded as a distinct neoplasm, whereas rhabdoid differentiation in adult renal cell carcinoma is usually found in association with conventional (clear cell) tumor, from which it is thought to evolve.

OBJECTIVE

To further characterize the rhabdoid phenotype in adult renal cell carcinoma and to determine its origin by genetic analysis.

DESIGN

We performed histologic, immunophenotypic, and genetic analyses on 5 cases of adult renal cell carcinoma with rhabdoid differentiation, 3 samples of adjacent conventional (clear cell) tumor, and 6 conventional (clear cell) control tumors.

RESULTS

Rhabdoid tumors differed from conventional (clear cell) carcinoma as follows: (1) macroscopically, rhabdoid tumors were solid white uniform masses; (2) microscopically, they had large rhabdoid cells with abundant eosinophilic cytoplasm, reduced lipid content, and the absence of a branching vascular pattern; and (3) biologically, they had a high metastatic potential. Despite these differences, loss of chromosome 3p in both the rhabdoid and clear cell carcinoma samples from 1 patient suggested a clonal origin. An identical mutation of the VHL gene in both rhabdoid and clear cell tumor samples from 2 patients confirmed a clonal origin for the histologically distinct tumor types in those cases.

CONCLUSION

Adult rhabdoid renal cell carcinoma can in some cases arise from conventional (clear cell) renal carcinoma and should be considered a clinically important form of renal cell carcinoma separate from, but analogous to, sarcomatoid change.

Pseudomesotheliomatous adenocarcinoma of the lung with rhabdoid features

Pseudomesotheliomatous adenocarcinoma of the lung is a rare entity, clinically and pathologically mimicking diffuse malignant pleural mesothelioma. We report a case of pseudomesotheliomatous adenocarcinoma consisting of two distinct histopathologic components with marked differences in morphological appearance and immunohistochemical staining pattern: a small subpleural nodule consisting of adenocarcinoma and undifferentiated carcinoma with rhabdoid features, the latter extending to the visceral pleura in a diffuse mesothelioma-like growth pattern. The adenocarcinomatous component showed strong reactivity with various epithelial markers, but no reactivity with vimentin. The undifferentiated component showed strong reactivity for vimentin, but no reactivity for epithelial markers. Both components showed no reactivity with CEA, Ber Ep4, MOC-31, B72.3, cytokeratin 5/6, calretinin and thrombomodulin. Metastatic lesions in the duodenum and the periumbilical skin consisted entirely of undifferentiated carcinoma with rhabdoid features. Fluorescence in situ hybridisation (FISH) was performed for chromosomes 4, 7, 20, and 22. FISH results showed polysomy 7 in both components. The diagnosis of pseudomesotheliomatous adenocarcinoma in this case was based on the finding of the subpleural nodule. We conclude that in cases of undifferentiated malignant pleural tumors with cells of rhabdoid phenotype, the possibility of peripheral pulmonary adenocarcinoma dedifferentiating into a more aggressive phenotype should be considered.

Treatment of metastatic rhabdoid tumor of the kidney

Metastatic rhabdoid tumor of the kidney (RTK) is a highly lethal malignancy; only one survivor with stage 4 disease has been reported. The authors reviewed the cases of two patients with metastatic RTK who had excellent responses to therapy. Both patients were treated with radiation therapy and alternating courses of ifosfamide, carboplatin, and etoposide (ICE) and vincristine, doxorubicin, and cyclophosphamide (VDC). The patients are without evidence of disease at 24 months and 12 months from the detection of metastasis. Alternating courses of ICE and VDC have activity against metastatic RTK. This combination of agents warrants prospective investigation in clinical trials.

Primary renal lymphoma and hypercalcemia in a child

Renal lymphoma is most frequently due to secondary lymphomatous infiltration of the kidneys in advanced stage disease. Rarely, are the kidneys the tissue of origin. We describe a 15-year-old male presenting with hypercalcemia and acute renal failure, due to a bilateral "primary B-cell lymphoma of the kidneys". The diagnosis was established by percutaneous needle biopsy of the right kidney. His disease was metastatic to multiple bones. His presenting features radiological findings and biopsy results are unique. We report his case, and review the pediatric literature.

Primary Ewing's sarcoma/primitive neuroectodermal tumor of the kidney: a clinicopathologic and immunohistochemical analysis of 11 cases

Ewing's sarcoma/primitive neuroectodermal tumor (ES/PNET) is an extraordinarily rare primary tumor in the kidney and can be mistaken for a variety of other round cell tumors, including blastema-predominant Wilms' tumor (WT). Approximately 90% of ES/PNET have a specific t(11;22), which results in a chimeric EWS-FLI-1 protein. Immunohistochemistry for the carboxy-terminus of FLI-1 is sensitive and highly specific for the diagnosis of ES/PNET. WT-1, the WT-associated tumor suppressor gene, is overexpressed in WT but not in ES/PNET. No study has examined FLI-1 or WT-1 expression in renal ES/PNET. The clinicopathologic features of 11 renal ES/PNET were studied along with immunohistochemistry for cytokeratin, desmin, CD99, FLI-1, and WT-1. WT were also immunostained for CD99 (5 cases), FLI-1 (10 cases), and WT-1 (9 cases). The patients (6 men, 5 women) ranged from 18 to 49 years of age (mean, 34 yr). The mean tumor size was 11.8 +/- 3.8 cm (mean +/- standard deviation). Presenting symptoms included abdominal/flank pain and/or hematuria. Grossly, all tumors showed necrosis and hemorrhage, and 4 had cystic change. Microscopically, all tumors showed vaguely lobular growth, primitive round cells, and variable rosette formation. Epithelial, myogenous, or cartilaginous differentiation was not seen. Immunohistochemical results on the renal ES/PNET were cytokeratin (2/8 focal), desmin (0/9), CD99 (8/8), FLI-1 (5/8), and WT-1 (0/8). In comparison, the WT only rarely expressed CD99 (1/5) and did not express FLI-1 (0/10), but were usually WT-1-positive (7/9). Follow-up on 8 cases (mean, 28 mo; range, 6-64 mo) showed 4 lung and pleural metastases, 1 bone metastasis, liver metastasis, 2 local recurrences, and 5 deaths from disease (median time to death, 16.8 mo). No case had distant metastatic disease at presentation. Adjuvant therapy included chemotherapy (8 cases), radiation (3 cases), and bone marrow transplantation (1 case). Our study affirms a unique proclivity of renal ES/PNET for young adults and that it is a highly aggressive neoplasm, with rapid death in many cases, usually after the development of treatment-resistant lung metastases. These tumors must be distinguished from blastema-predominant WT and other primitive renal tumors that require different therapy. FLI-1 and WT-1 immunohistochemistry may be valuable in this differential diagnosis, given the known immunophenotypic overlap between ES/PNET and blastema-predominant WT with regard to CD99, cytokeratin, and desmin. The accurate distinction between these two entities has clear prognostic and therapeutic implications.

Renal cell carcinoma with rhabdoid features

Neoplasms with rhabdoid features have been reported at many anatomic sites. In the kidney, rhabdoid tumors are typically found in children, whereas only rare examples have been reported in adults. Little is known of renal cell carcinomas (RCCs) that exhibit rhabdoid features. The objective of this study was to determine the incidence of RCC with rhabdoid attributes and characterize the histologic, immunophenotypic, and ultrastructural features by retrospective analysis of 480 consecutively identified cases of RCC in radical nephrectomy specimens. Immunohistochemical evaluation was performed in cases with rhabdoid foci using a panel of antibodies to pancytokeratin (pan-CK), CK7, CK20, epithelial membrane antigen (EMA), S-100 protein, desmin, vimentin, neuron-specific enolase (NSE), muscle-specific actin (MSA), smooth muscle actin (SMA), human melanoma, black-45 (HMB-45), and glial fibrillary acidic protein (GFAP). Electron microscopy was also performed in selected cases. The presence and extent of rhabdoid foci in relation to pathologic stage and grade were assessed. Twenty-three of 480 cases of RCC (4.7%) exhibited rhabdoid features. The 23 patients were all adults with a mean age of 61.8 years (age range, 33-84 yrs). Fifteen of the patients were men and eight were women. Histologically, the rhabdoid foci were typified by sheets and clusters of variably cohesive, large epithelioid cells with vesicular and often eccentric nuclei, prominent nucleoli, and large, paranuclear intracytoplasmic hyaline globules (inclusions). The presence of these rhabdoid features was related to high histologic Fuhrman grade of the nonrhabdoid carcinoma component, with an incidence of 0 of 84 grade I cases, eight of 300 grade 2 cases (2.6%), six of 70 grade 3 cases (8.9%), and nine of 26 grade 4 cases (34.6%; p = 3 x 10(-9)). The rhabdoid foci were all high grade. The presence of rhabdoid foci was also found in higher stage carcinomas. A total of 52% (12 of 23) of RCC cases with rhabdoid features exhibited extrarenal extension compared with 28% (24 of 92) of contemporary RCCs without rhabdoid features (p = 0.03). The size of the rhabdoid component ranged from 1 mm to more than 2 cm and comprised 1% to 50% of the renal mass. Immunoreactivity for vimentin (100%), NSE (79%), and panCK (56%) was present in the majority of cases. Substantial percentages of cases were immunopositive for EMA (47%) and S-100 protein (37%), with minimal to no immunohistochemical reactivity for CK7 (5%), SMA (5%), CK20 (0%), desmin (0%), MSA (0%), HMB-45 (0%), and GFAP (O%). A distinctive globular, paranuclear reaction pattern was found for the cytokeratin, EMA, and vimentin immunostains. Ultrastructurally, the rhabdoid cells had paranuclear intermediate filament aggregates or paranuclear condensation of organelles, often associated with peripheral vacuolization. Adult RCCs may harbor a rhabdoid component, and these neoplasms can be regarded as "composite" tumors. Rhabdoid elements are important to identify because of their high-grade nature, and association with high stage. Adult RCC with rhabdoid elements should be distinguished from pure rhabdoid tumors of kidney, in light of their clinicopathologic differences. Rhabdoid differentiation in adult renal cell carcinoma may represent clonal divergence and/ or evolution, and emergence of a particularly aggressive element.

Inv(11)(p13p15) and myf-3(MyoD1) in a malignant extrarenal rhabdoid tumor of a premature newborn

We present a premature newborn of 32 wk of gestation with a congenital malignant extrarenal rhabdoid tumor (MERT) on the right shoulder with generalized metastases. Standard histologic, immunohistochemical, molecular and cytogenetic methods were used in the evaluation of diagnostic material. Biopsy of a skin lesion showed the histologic features of a malignant rhabdoid tumor. Cytogenetic analysis of the tumor cells revealed an inv(11)(p13p15) and additionally, an increased expression of myf-3 (myogenic determination factor, MyoD1) and PAX3 was detected. These results suggest an origin of the neoplasm derived from a pluripotent cell with the potential of myogenic differentiation. Tumor suppressor genes located on chromosome 11p13 and 11p15 may play an important role for malignant rhabdoid tumor development and progression.

Adenocarcinoma of the renal pelvis with vimentin-positive intracytoplasmic inclusions

A case of mucus-producing papillary adenocarcinoma of the renal pelvis associated with multiple renal calculi in a 16-year-old male is reported. The majority of the tumor cells contained large, round or cone-shaped, vimentin-positive intracytoplasmic inclusions, which exhibited some morphological and immunohistochemical resemblance to inclusions found in malignant rhabdoid tumor of the kidney. An intracytoplasmic accumulation of mucus was also noted in some tumor cells. The patient is free from recurrence and metastasis after a nephrectomy.

Synovial sarcoma of the extremities: a clinicopathologic study of 34 cases, including semi-quantitative analysis of spindled, epithelial, and poorly differentiated areas

Many clinicopathologic studies of synovial sarcoma have grouped together tumors from different sites. The goal of this study was to identify clinical and pathologic features that correlate with a poor outcome in patients with extremity synovial sarcoma. Thirty-four cases of synovial sarcoma of the extremities were studied. Inclusion criteria included a consistent histology, the immunohistochemical expression of at least one epithelial marker (AE1/3, CAM 5.2, or epithelial membrane antigen), and adequate clinical follow-up. Features evaluated included the presence and extent of spindled, epithelial, and poorly differentiated areas, the presence and extent of calcification and necrosis, nuclear grade, the presence or absence of cells with a rhabdoid morphology, and the number of mitotic figures (MFs) per 10 high power fields (HPFs). Patients were considered to have an adverse outcome if they developed metastatic disease or died from tumor. The cohort included 15 males and 19 females with a median age 36 years (range, 11-82 years). There were 22 lower extremity tumors and 12 located on the upper extremities. Tumor size ranged from 1.2 to 16 cm (median, 6 cm). Follow-up ranged from 9 to 108 months (median, 38 months). Eleven (32%) patients had an adverse outcome, all with metastatic disease. Features associated with an adverse outcome included increasing age (p = 0.04), tumor size of 5 cm or greater (p = 0.03), tumor location on the lower extremities (p = 0.04), the presence of poorly differentiated areas (p = 0.04), grade 3 nuclei (p = 0.005), cells with a rhabdoid morphology (p = 0.003), and more than 10 MFs/10 HPFs (p = 0.005). Patients whose tumors were composed of at least 20% poorly differentiated areas were significantly more likely to have an adverse outcome (p < 0.001). In conclusion, a variety of clinical and pathologic features are associated with an adverse outcome in patients with synovial sarcoma of the extremities. These features include increasing age, tumor size of 5 cm or more, lower extremity tumor location, the presence of poorly differentiated areas, particularly when at least 20% of the tumor, grade 3 nuclei, rhabdoid cells, and more than 10 MFs/10 HPFs.