Renal medullary carcinoma: rhabdoid features and the absence of INI1 expression as markers of aggressive behavior

Generation of a mouse model of atypical teratoid/rhabdoid tumor of the central nervous system through combined deletion of Snf5 and p53

Malignant rhabdoid tumors arise in several anatomic locations and are associated with poor outcomes. In the brain, these tumors are known as atypical teratoid/rhabdoid tumors (AT/RT). While genetically engineered models for malignant rhabdoid tumors exist, none of them recapitulate AT/RT, for which preclinical models remain lacking. In the majority of AT/RT, LOH occurs at the genetic locus SNF5 (Ini1/BAF47/Smarcb1), which functions as a subunit of the SWI/SNF chromatin-remodeling complex and a tumor suppressor in familial and sporadic malignant rhabdoid tumors. Therefore, we generated mice in which Snf5 was ablated specifically in nestin-positive and/or glial fibrillary acid protein (GFAP)-positive progenitor cells of the developing central nervous system (CNS). Snf5 ablation in nestin-positive cells resulted in early lethality that could not be rescued by loss of p53. However, Snf5 ablation in GFAP-positive cells caused a neurodegenerative phenotype exacerbated by p53 loss. Notably, these double mutants exhibited AT/RT development, associated with an earlier failure in granule neuron migration in the cerebellum, reduced neuronal projections in the hippocampus, degeneration of the corpus callosum, and ataxia and seizures. Gene expression analysis confirmed that the tumors that arose in Snf5/p53 mutant mice were distinct from other neural tumors and most closely resembled human AT/RT. Our findings uncover a novel role for Snf5 in oligodendrocyte generation and survival, and they offer evidence of the first genetically engineered mouse model for AT/RT in the CNS.

An update on the application of newly described immunohistochemical markers in soft tissue pathology

CONTEXT

During the last 5 to 10 years, significant progress has been made in the molecular characterization of soft tissue tumors, predominantly with the identification of recurrent translocations or amplification of certain genes in different tumor types. Alongside this, translational efforts have identified many novel and diagnostically useful immunohistochemical markers for many of these tumor types.

OBJECTIVE

This article reviews a select group of recently described immunohistochemical markers of particular use in the evaluation of mesenchymal neoplasms; the underlying biology of the protein product, practical utility, and limitations of each marker are discussed in detail.

DATA SOURCES

Literature review, authors' research data, and personal practice experience serve as sources.

CONCLUSIONS

There are many diagnostically useful immunohistochemical markers to help confirm the diagnosis of many different soft tissue tumor types, some of which have reduced the need for additional, and more costly, studies, such as fluorescence in situ hybridization. However, no one marker is 100% specific for a given tumor, and knowledge of potential pitfalls and overlap in patterns of staining among other tumor types is crucial to ensure the appropriate application of these markers in clinical practice.

Papillary or pseudopapillary tumors of the kidney

Papillary architecture is one of the most common morphological patterns in renal cell neoplasms. Many renal cell neoplasms can also exhibit, diffusely or focally, papillary growth pattern. This article reviews all the renal cell neoplasms with papillary or pseudopapillary architecture, with an emphasis on recently described new histological types. New insights into the "old" entities, including their immunohistochemical and genetic features, will also be discussed.

Immunohistochemistry in undifferentiated neoplasm/tumor of uncertain origin

CONTEXT

Immunohistochemistry has become an indispensable ancillary study in the identification and classification of undifferentiated neoplasms/tumors of uncertain origin. The diagnostic accuracy has significantly improved because of the continuous discoveries of tissue-specific biomarkers and the development of effective immunohistochemical panels.

OBJECTIVES

To identify and classify undifferentiated neoplasms/tumors of uncertain origin by immunohistochemistry.

DATA SOURCES

Literature review and authors' research data and personal practice experience were used.

CONCLUSIONS

To better guide therapeutic decisions and predict prognostic outcomes, it is crucial to differentiate the specific lineage of an undifferentiated neoplasm. Application of appropriate immunohistochemical panels enables the accurate classification of most undifferentiated neoplasms. Knowing the utilities and pitfalls of each tissue-specific biomarker is essential for avoiding potential diagnostic errors because an absolutely tissue-specific biomarker is exceptionally rare. We review frequently used tissue-specific biomarkers, provide effective panels, and recommend diagnostic algorithms as a standard approach to undifferentiated neoplasms.

The expanding family of SMARCB1(INI1)-deficient neoplasia: implications of phenotypic, biological, and molecular heterogeneity

Since the description of atypical teratoid/rhabdoid tumors of the central nervous system and renal/extrarenal malignant rhabdoid tumors in children, the clinicopathologic spectrum of neoplasms having in common a highly variable rhabdoid cell component (0% to 100%) and consistent loss of nuclear SMARCB1 (INI1) expression has been steadily expanding to include cribriform neuroepithelial tumor of the ventricle, renal medullary carcinoma and a subset of collecting duct carcinoma, epithelioid sarcoma, subsets of miscellaneous benign and malignant soft tissue tumors, and rare rhabdoid carcinoma variants of gastroenteropancreatic, sinonasal, and genitourinary tract origin. Although a majority of SMARCB1-deficient neoplasms arise de novo, the origin of SMARCB1-deficient neoplasia in the background of a phenotypically or genetically definable differentiated SMARCB1-intact "parent neoplasm" has been convincingly demonstrated, highlighting the rare occurrence of rhabdoid tumors as "double-hit neoplasia." As a group, SMARCB1-deficient neoplasms occur over a wide age range (0 to 80 y), may be devoid of rhabdoid cells or display uniform rhabdoid morphology, and follow a clinical course that varies from benign to highly aggressive causing death within a few months irrespective of aggressive multimodality therapy. Generally applicable criteria that would permit easy recognition of these uncommon neoplasms do not exist. Diagnosis is based on site-specific and entity-specific sets of clinicopathologic, immunophenotypic, and/or molecular criteria. SMARCB1 immunohistochemistry has emerged as a valuable tool in confirming or screening for SMARCB1-deficient neoplasms. This review summarizes the different phenotypic and topographic subgroups of SMARCB1-deficient neoplasms including sporadic and familial, benign and malignant, and rhabdoid and nonrhabdoid variants, highlighting their phenotypic heterogeneity and molecular complexity.

Clinicopathological characteristics of anaplastic carcinoma of the pancreas with rhabdoid features

Undifferentiated (anaplastic) carcinoma with rhabdoid features is a rare and aggressive subtype of pancreatic carcinoma. Here, we report the clinical, histological, and immunohistochemical phenotypes in six autopsy cases of anaplastic carcinoma with rhabdoid features. The patients ranged between 44 and 76 years of age (median, 61 years) and consisted of four males and two females. All patients except one case died within 3 months of diagnosis, as these tumors were found at an advanced stage and were chemoresistant. At autopsy, tumor masses measuring 4-22 cm in maximum diameter were mainly located in the pancreatic body and tail. Microscopically, all cases showed anaplastic carcinoma with rhabdoid features that were discohesive with round to polygonal eosinophilic cytoplasm with occasional inclusions, and that had vesicular nuclei, and prominent nucleoli. Immunohistochemistry showed that the rhabdoid cells, particularly the inclusions, were strongly positive for pan-cytokeratin (AE1/AE3) and vimentin. Meanwhile, downregulation or aberrant cytoplasmic localization with focal aggregation of E-cadherin, β-catenin, and EMA were frequently observed in the rhabdoid cells. Moreover, the intracytoplasmic inclusions were labeled with selective autophagy-related molecules including p62/SQSTM1, ubiquitin, and kelch-like ECH-associated protein 1 (KEAP1). In addition, nuclear factor erythroid 2-related factor 2 (NRF2) and overexpression of its target molecule multidrug resistance-associated protein 1 (MRP1) were commonly observed in the rhabdoid cells. Therefore, these results suggest that p62-mediated aggregation of ubiquitinated intermediate filaments and membranous proteins is an important phenomenon in the rhabdoid phenotype. Indeed, the ubiquitinated aggregates of p62 and KEAP1 would induce activation of NRF2 and upregulation of MRP1, leading to potential chemoresistance of anaplastic carcinoma with rhabdoid features.

SMARCB1 (INI-1)-deficient carcinomas of the sinonasal tract

SMARCB1 (INI-1) is a tumor-suppressor gene located on chromosome 22q11.2. Its gene product is ubiquitously expressed in nuclei of all normal tissues. SMARCB1 gene inactivation has been implicated in the pathogenesis of a diverse group of malignant neoplasms that tend to share "rhabdoid" cytomorphology. This group of SMARCB1-deficient tumors is now further expanded by a subset of carcinomas arising in the sinonasal tract. SMARCB1 immunostaining was performed on 142 sinonasal carcinomas. Tumors that showed loss of expression were further characterized for SMARCB1 deletions by fluorescence in situ hybridization. Nine of 142 (6%) primary sinonasal carcinomas showed loss of SMARCB1 expression by immunohistochemistry. Five patients were women, and patients ranged in age from 33 to 78 years (mean 59 y). The SMARCB1-deficient tumors were characterized by nests, sheets, and cords of cells without any histologic evidence of specific (eg, squamous or glandular) differentiation. The tumors comprised varying proportions of basaloid and rhabdoid cells. The SMARCB1-deficient carcinomas had been diagnosed as nonkeratinizing squamous cell carcinomas (n=3), sinonasal undifferentiated carcinomas (n=2), myoepithelial carcinoma (n=2), nonintestinal adenocarcinoma (n=1), and carcinoma, not otherwise specified (n=1). Fluorescence in situ hybridization analysis revealed SMARCB1 deletions in 6 of 8 (75%) carcinomas. The SMARCB1-deficient carcinomas did not harbor human papillomavirus or NUT-1 alterations. Six patients presented with T4 disease, 5 patients developed local recurrences and/or distant metastases, and 4 died of their disease. Inactivation of the SMARCB1 tumor-suppressor gene appears to be involved in the pathogenesis of a subset of sinonasal carcinomas, further expanding the family of SMARCB1-deficient neoplasms and further delineating a bewildering group of poorly/undifferentiated, aggressive carcinomas arising at this site. The ability to detect SMARCB1 loss by immunohistochemistry, particularly when dealing with poorly differentiated carcinomas with basaloid or rhabdoid features, should facilitate a more comprehensive understanding of these sinonasal carcinomas including clinical behavior and response to targeted therapies.

Rhabdoid differentiation is associated with aggressive behavior in renal cell carcinoma: a clinicopathologic analysis of 76 cases with clinical follow-up

Rhabdoid differentiation has been associated with aggressive behavior in carcinomas from different organ systems. A recent consensus statement of the International Society of Urological Pathology (ISUP), in addition to proposing a nucleolar grading system (ISUP grade) for renal cell carcinoma (RCC) to replace the Fuhrman system, recommended reporting the presence of rhabdoid differentiation in RCC and considering tumors with rhabdoid differentiation to be ISUP grade 4. Although it has been shown that rhabdoid differentiation is associated with increased grade and stage of RCC, it has not been fully demonstrated whether it has an adverse effect independent of this association with increased grade and stage. We provide the largest clinicopathologic analysis of RCC with rhabdoid differentiation to date (76 cases), including characterization of metastatic disease. In addition, by constructing a multivariable model including tumor grade, stage, necrosis, and distant metastasis to compare a series of 49 clear cell RCC with rhabdoid differentiation with a cohort of 41 clear cell RCCs without rhabdoid differentiation, we demonstrate that the presence of rhabdoid differentiation in clear cell RCC confers an increased risk of death (hazard ratio=5.25; 95% confidence interval, 2.1-14.3) independent of these other adverse prognostic factors. These findings underscore the significance of rhabdoid differentiation in RCC as an adverse prognostic factor and support the recent reporting and grading recommendations of the ISUP.

SMARCB1 deletion by a complex three-way chromosomal translocation in an extrarenal malignant rhabdoid tumor

Rhabdoid tumors (RTs) are highly aggressive malignant neoplasms of early childhood that arise in the kidney, brain, and extrarenal sites. The disease is genetically defined by biallelic disruption of the SMARCB1/INI1/SNF5 tumor suppressor gene, a core component of the ATP-dependent chromatin remodeling SWI/SNF complex. The molecular changes leading to SMARCB1 alterations in RTs are heterogeneous, including germline or constitutional inactivating mutations, partial or total gene deletions, copy number neutral loss of heterozygosity, and, less commonly, reciprocal translocations. We report a novel three-way chromosomal rearrangement, which was identified by conventional cytogenetic and sequential fluorescence in situ hybridization studies as the underlying molecular mechanism of the loss of SMARCB1 in an extrarenal RT. This case highlights the heterogeneity of genetic events that may lead to the loss of SMARCB1 and the development of RTs.

Pathology and diagnosis of SMARCB1-deficient tumors

Malignant rhabdoid tumor (MRT) can occur in the kidney, central nervous system, or extracranial/extrarenal locations and is characterized by alterations in the SMARCB1 gene. The tumors occur in infants and young children and confer a poor prognosis requiring aggressive therapeutic interventions to improve the chances for survival. MRTs pose a diagnostic challenge, as they display heterogeneous histopathologic features and differentiate along multiple lineages. The identification of alterations in the SMARCB1 gene in MRT using immunohistochemical (IHC) staining has lead to improved diagnosis of MRT as well as the discovery of the loss of SMARCB1 expression in some non-MRTs. Whether loss of SMARCB1 plays a pathogenic role in nonrhabdoid tumors remains to be determined; however, most of these tumors lack the clinical and other molecular features of MRT. We review the histopathologic features of MRT and the importance and significance of loss of expression of SMARCB1 in both MRT and nonrhabdoid tumors.

VCL-ALK renal cell carcinoma in children with sickle-cell trait: the eighth sickle-cell nephropathy?

We report the third case of a renal cell carcinoma bearing a fusion of the vinculin (VCL) and anaplastic lymphoma kinase (ALK) genes. Like the 2 other reported cases, this neoplasm occurred in a young patient (6 y old) with sickle-cell trait and demonstrated distinctive morphologic features including medullary epicenter, discohesive polygonal or spindle-shaped cells with prominent cytoplasmic vacuoles, and prominent lymphocytic infiltrate. The neoplastic cells demonstrated focal membranous labeling for ALK protein by immunohistochemistry, ALK gene rearrangement by fluorescence in situ hybridization, and a specific VCL-ALK gene fusion by reverse transcriptase polymerase chain reaction. VCL-ALK renal cell carcinoma may represent the eighth sickle-cell nephropathy.

Novel uses of immunohistochemistry in the diagnosis and classification of soft tissue tumors

Immunohistochemistry plays a key role in the diagnosis of soft tissue tumors. Until recently, however, the primary purpose of immunohistochemistry in this context was simply to attempt to demonstrate a line of differentiation. Unfortunately, most traditional markers (predominantly directed against cytoplasmic determinants) show relatively limited specificity. Over the last decade or so, much more specific immunohistochemical markers for soft tissue tumors have been developed. This review will provide an update of some of the most useful new diagnostic markers, which are significantly changing clinical practice for surgical pathologists, separated into three general categories: (1) lineage-restricted transcription factors, (2) protein correlates of molecular alterations, and (3) diagnostic markers identified by gene expression profiling.

Prognostic value of MIB-1, p53, epidermal growth factor receptor, and INI1 in childhood chordomas

BACKGROUND

Chordomas are slow-growing tumors and most commonly involve the sacrum and clivus. Multiple recurrences are frequent. Childhood chordomas are rare and often show exceptionally aggressive behavior, resulting in short survival and a high incidence of metastatic spread.

OBJECTIVE

This study examined the histologic features and immunohistochemical profile of pediatric chordomas and compared them with their adult counterparts.

METHODS

Nine pediatric and 13 adult cases were included in the study. Childhood chordomas were classified into conventional, atypical, and poorly differentiated types. Immunohistochemistry was performed for cytokeratin, epithelial membrane antigen, vimentin, S100, brachyury, p53, INI1, epidermal growth factor receptor (EGFR), and CD117. Cytogenetic analyses were performed in a subset of tumors for SMARCB1/INI1 locus on 22q chromosome by fluorescent in situ hybridization (FISH) and analysis of the SMARCB1/INI1 gene sequence.

RESULTS

All tumors showed expression of cytokeratin, epithelial membrane antigen, S100, vimentin, brachyury, and EGFR. Atypical morphology, p53 expression, higher MIB-1 labelling index (LI), and INI1 loss were more frequently seen in pediatric chordomas as compared with adults. None of the tumors showed CD117 expression. No point mutation in the SMARCB1/INI1 gene was noted in the tumors examined; however, 4 pediatric and 1 adult chordoma showed loss of this locus on FISH analysis.

CONCLUSIONS

A subset of pediatric chordomas with atypical histomorphologic features needs to be identified, as they behave in an aggressive manner and require adjuvant therapy. Pediatric chordomas more frequently show p53 expression, INI1 loss, and higher MIB-1 LI as compared with adults, whereas EGFR expression is common to both.

Renal medullary cancer in a patient with sickle cell trait

Renal medullary cancer is a rare malignancy almost exclusively seen in young patients of African ethnicity. These patients often present with the cardinal symptoms of hematuria, flank pain, and an abdominal mass, and this malignancy has been associated with patients carrying sickle cell trait. It is estimated that 300 million people worldwide carry sickle cell trait, and the presence of hematuria in these patients should be treated as a harbinger of a possible malignancy. Notably, this tumor mostly develops on the right side of the body. Patients often present with it at an advanced stage and the prognosis is poor. Therefore, a high index of suspicion in a patient of African descent presenting with a right sided abdominal mass and hematuria may assist in an early diagnosis. Current chemotherapy options are very limited, and early detection may provide a chance for surgical resection. It may also provide a bigger time frame for the initiation of novel chemotherapy regimens in patients who fail current chemotherapy regimens.

Immunohistochemical expression of glypican-3 in pediatric tumors: an analysis of 414 cases

Glypican-3 (GPC3) is a proteoglycan thought to play an important role during development. Germline GPC3 mutations are seen in the rare Simpson-Golabi-Behmel syndrome (SGBS), which predisposes patients to Wilms tumor, hepatoblastoma, and neuroblastoma. While numerous adult tumors have been evaluated by immunohistochemistry for GPC3, no comprehensive assessment has been done in pediatric tumors. We therefore investigated GPC3 expression in 143 pediatric central nervous system (CNS) tumors and 271 non-CNS tumors. Among non-CNS tumors, GPC3 expression was seen in 9/9 (100%) hepatoblastomas, 4/6 (67%) malignant rhabdoid tumors, 5/13 (38%) Wilms tumors, 11/37 (30%) alveolar rhabdomyosarcomas, and 8/45 (18%) embryonal rhabdomyosarcomas. All 136 neuroblastomas, 14 Ewing sarcoma/primitive neuroectodermal tumors, and 11 synovial sarcomas were immunonegative for GPC3. Among CNS tumors, GPC3 had restricted expression, with positivity in 6/6 (100%) atypical teratoid rhabdoid tumors and 1/4 (25%) craniopharyngiomas. The remaining 136 CNS tumors-23 medulloblastomas, 21 pilocytic astrocytomas, 13 gangliogliomas, 12 ependymomas, 12 glioblastomas, 11 choroid plexus neoplasms, 10 diffuse astrocytomas (grade II/III), 10 meningiomas, 8 dysembryoplastic neuroepithelial tumors, 8 oligodendrogliomas, 3 craniopharyngiomas, 3 germinomas, and 2 neurocytomas-were entirely negative for GPC3. These results showed GPC3 positivity in a number of non-CNS tumors, with no consistent discrimination between tumors that were or were not associated with SGBS. Within the CNS, GPC3 positivity was limited to a small subset of CNS neoplasms and may thus serve as a useful positive diagnostic biomarker (P < 0.0001) in addition to negative INI1/BAF47/SMARCB1 staining to differentiate atypical teratoid rhabdoid tumors from other high-grade pediatric brain tumors.

Cutaneous syncytial myoepithelioma: clinicopathologic characterization in a series of 38 cases

Cutaneous myoepithelial tumors demonstrate heterogenous morphologic and immunophenotypic features. We previously described, in brief, 7 cases of cutaneous myoepithelioma showing solid syncytial growth of ovoid, spindled, or histiocytoid cells. We now present the clinicopathologic features in a series of 38 cases of this distinctive syncytial variant, which were diagnosed between 1997 and 2012 (mostly seen in consultation). There were 27 men and 11 women, with a median age of 39 years (range, 2 mo to 74 y). Primary anatomic sites were the upper extremity (11, including 2 on the hand), upper limb girdle (3), lower extremity (14; 3 on the foot), back (6), face (2), chest (1), and buttock (1); the typical presentation was as either a polypoid or papular lesion. Tumors were well circumscribed and centered in the dermis and ranged in size from 0.3 to 2.7 cm (median 0.8 cm). Microscopically all tumors showed a solid sheet-like growth of uniformly sized ovoid to spindled or histiocytoid cells with palely eosinophilic syncytial cytoplasm. Nuclei were vesicular with fine chromatin and small or inconspicuous nucleoli and exhibited minimal to no atypia. Mitoses ranged from 0 to 4 per 10 HPF; 28 tumors showed no mitoses. Necrosis and lymphovascular invasion were consistently absent. Adipocytic metaplasia, appearing as superficial fat entrapped within the tumor, was seen in 12 cases. Chondro-osseous differentiation was seen in 1 tumor. All tumors examined were diffusely positive for EMA, and the majority showed diffuse staining for S-100 protein (5 showing focal staining). Keratin staining was focal in 1 of 33 tumors and seen in rare cells in 3 other cases. There was also positivity for GFAP (14/33), SMA (9/13), and p63 (6/11). Most lesions were treated by local excision. The majority of tumors tested (14/17; 82%) were positive by fluorescence in situ hybridization for EWSR1 gene rearrangement; testing for potential fusion partners (PBX1, ZNF444, POU5F1, DUX4, ATF1, CREB1, NR4A3, DDIT3, and NFATc2) was negative in all EWSR1-rearranged tumors. No FUS gene rearrangement was detected in 2 tumors lacking EWSR1 rearrangement. Follow-up information is available for 21 patients (mean follow-up 15 mo). One patient with a positive deep margin developed a local recurrence 51 months after initial biopsy. All other patients with available follow-up information, including 11 who had positive deep margins, are alive with no evidence of disease and no reported metastases. In summary, cutaneous syncytial myoepithelioma is a morphologically distinct variant that more frequently affects men, occurs over a wide age range, and usually presents on the extremities. Tumors are positive for S-100 protein and EMA, and, unlike most myoepithelial neoplasms, keratin staining is infrequent. EWSR1 gene rearrangement is present in nearly all tumors tested and likely involves a novel fusion partner. Prior reports describe some risk of recurrence and metastasis for cutaneous myoepithelial tumors; however, the syncytial variant appears to behave in a benign manner and only rarely recurs locally.

Renal Medullary Carcinoma Masquerading as Bilateral Breast Carcinoma Category: Case Report

Metastatic disease to the breast accounts for less than 1% of all breast carcinoma. Here we describe an unusual case of a 34-year-old black female with history of sickle cell trait who presented to her gynecologist with bilateral palpable breast masses. Based on initial workup including pathology results from biopsies of both breast masses, she was diagnosed with bilateral breast cancer. However further radiographic imaging revealed a large right kidney mass suspicious for primary renal neoplasm along with lung and bone lesions. This prompted re-review of the initial breast pathology. Sickled erythrocytes were identified and results of an additional immunohistochemical panel revealed positive expression of PAX 8, vimentin, Oct3/4, and loss of INI1, confirming the diagnosis of metastatic renal medullary carcinoma. We discuss the importance of considering renal medullary carcinoma in the differential diagnosis when evaluating young patients with sickle cell hemoglobinopathies who present with aggressive metastatic disease.

Renal medullary carcinoma: molecular, immunohistochemistry, and morphologic correlation

Renal medullary carcinoma, a highly aggressive tumor mainly occurring in patients with sickle cell hemoglobinopathy, is characterized by advanced stage at the time of presentation and poor response to treatment. Currently, the pathogenesis of this tumor is not well understood. In this study, the clinicopathologic features and molecular changes of 15 renal medullary carcinoma cases were evaluated. These cases demonstrated male predominance (M:F=2:1) with a median age of 26 years. The tumors occurred predominantly in the right kidney with an average size of 5.9 cm. Immunohistochemistry analysis showed that the neoplastic cells were positive for CEA (7/8), AE1/3 (8/8), CAM5.2 (7/7), CK7 (5/5), CK20 (4/6), and vimentin (6/6). Absence of SMARCB1 protein expression in tumor cells was demonstrated in all of the 7 cases analyzed. By polymerase chain reaction-based microsatellite analysis, loss of heterozygosity of SMARCB1 was identified in 9 of 10 cases. These data suggest that inactivation of SMARCB1 may play a role in the pathogenesis of renal medullary carcinoma.

Epithelioid sarcoma is associated with a high percentage of SMARCB1 deletions

SMARCB1 gene alterations were first described in highly malignant rhabdoid tumors of the kidney, brain (atypical teratoid/rhabdoid tumor) and soft tissue. An increasing number of tumors have now shown loss of SMARCB1 protein expression by immunohistochemistry, including the majority of epithelioid sarcomas. However, investigations of SMARCB1 gene alterations in epithelioid sarcoma have produced conflicting results. The aim of this study was to evaluate SMARCB1 status using Sanger sequencing of the coding region and multiplex ligation-dependent probe amplification, a rapid and sensitive method for detecting intragenic deletions and duplications, which has not been used in previous studies. Twenty-one epithelioid sarcomas of both classical and proximal type were selected for SMARCB1 gene testing and SMARCB1 immunohistochemistry. Nineteen of 21 (90%) epithelioid sarcomas were SMARCB1 negative by immunohistochemistry. Twelve of the 19 (63%) had adequate DNA recovery for evaluation. Ten of 12 (83%) tumors showed homozygous deletions of the gene. Two cases showed heterozygous deletions and polymorphisms, but no sequence mutations. These results confirm the high frequency of SMARCB1 deletions in epithelioid sarcoma and show that multiplex ligation-dependent probe amplification is a reliable method for detection of deletions in these cases, which can be performed on formalin-fixed, paraffin-embedded tissue. Given the high percentage of SMARCB1 alterations in epithelioid sarcoma, these findings argue against using SMARCB1 gene deletion as a tool in distinguishing them from malignant rhabdoid tumors.

[Chromatin remodeling defects and cancer: the SWI/SNF example]

The SWI/SNF complex is a multiprotein complex essential for chromatin remodelling. As such, it plays a key role in the epigenetic regulation of genome expression. This complex is composed of a dozen of proteins, some of which are constant and ubiquitous, especially SMARCB1 and SMARCA4. Mutations in these genes are now described in an increasing number of tumors. Mutations in SMARCB1 characterize the majority of rhabdoid tumors, an aggressive malignancy that exquisitely depends on this single genetic event. Rare rhabdoid tumors have mutation in SMARCA4, a genetic abnormality also found in some medulloblastomas. Many other tumor types, of variable aggressiveness, show an abnormal loss of expression of SMARCB1, but the genetic underlying cause most often remains elusive. The recent sequencings of whole exomes have described frequent mutations in other genes of the SWI/SNF complex: mutations in ARID1A in liver, gastric or bladder carcinomas, and PBRM1 mutations in renal cancers. These data establish the wide role of SWI/SNF complex in cancers and justify that major efforts should now be devoted to this common mechanism of human oncogenesis.

Nucleosome occupancy and gene regulation during tumorigenesis

Nucleosomes are the basic structural units of eukaryotic chromatin. In recent years, it has become evident that nucleosomes and their position, in concert with other epigenetic mechanisms (such as DNA methylation, histone modifications, changes in histone variants, as well as small noncoding regulatory RNAs) play essential roles in the control of gene expression. Here, we discuss the mechanisms and factors that regulate nucleosome position and gene expression in normal and cancer cells.

Carcinoma of the collecting ducts of Bellini and renal medullary carcinoma: clinicopathologic analysis of 52 cases of rare aggressive subtypes of renal cell carcinoma with a focus on their interrelationship

Carcinoma of the collecting ducts of Bellini and renal medullary carcinoma are rare aggressive neoplasms of putative distal nephron origin. First described in 1949, case reports and review articles constitute a major source of information on collecting duct carcinoma, whereas Davis and colleagues and the pediatric tumor registry have contributed the seminal works on renal medullary carcinoma. Here we present a detailed study of collecting duct carcinoma (n=39) and renal medullary carcinoma (n=13), characterizing these rare neoplasms and analyzing their interrelationship. Both collecting duct carcinoma and renal medullary carcinoma exhibited significant similarities, such as predilection for the right kidney, tumor mass with an epicenter in the renal medulla, and a mean size of 7 cm. Overall, both tumors exhibited a poorly differentiated adenocarcinoma histology with desmoplastic stromal response (100%), inflammatory infiltrate (100%), frequent perinephric extension (collecting duct carcinoma: 97%; renal medullary carcinoma: 83%), lymphovascular invasion (100%), intraluminal mucin (collecting duct carcinoma: 42%; renal medullary carcinoma: 73%), high nuclear grade (97%), overlapping immunoreactivity for Ulex europaeus agglutinin 1 (collecting duct carcinoma: 75%; renal medullary carcinoma:55%), CK7 (collecting duct carcinoma: 44%; renal medullary carcinoma: 71%), and high-molecular weight cytokeratin (collecting duct carcinoma: 26%; renal medullary carcinoma: 29%), and nonimmunoreactivity for Ksp-cadherin. Histologically, collecting duct carcinoma frequently had tubular, tubulopapillary, or irregular glandular architecture, whereas renal medullary carcinoma commonly demonstrated islands of anastomosing tubules and cords forming irregular microcystic spaces. Multiple metastases to the lymph nodes, lung, bone, and liver were observed in both categories at presentation (collecting duct carcinoma: 17%; renal medullary carcinoma: 36%). Only patients with organ-confined small tumors were disease free beyond the median survival time. Differential clinical features between collecting duct carcinoma and renal medullary carcinoma included proclivity for younger male individuals of African ancestry with hemoglobin abnormalities and a shorter median survival of 17 weeks (vs. 44 wk for collecting duct carcinoma) for renal medullary carcinoma. The markedly overlapping clinical features, histology, immunophenotype, metastasis patterns, and uniformly aggressive outcome in collecting duct and renal medullary carcinomas suggest that renal medullary carcinoma is a distinctive clinicopathologic subtype within the entity of collecting duct carcinoma. The extremely poor prognosis and ongoing clinical trials with specific therapeutic protocols argue for their accurate distinction from other renal cell carcinoma subtypes.

Molecular inversion probe analysis detects novel copy number alterations in Ewing sarcoma

Ewing sarcoma (ES) is the second most common bone tumor in children and young adults, with dismal outcomes for metastatic and relapsed disease. To better understand the molecular pathogenesis of ES and to identify new prognostic markers, we used molecular inversion probes (MIPs) to evaluate copy number alterations (CNAs) and loss of heterozygosity (LOH) in formalin-fixed paraffin-embedded (FFPE) samples, which included 40 ES primary tumors and 12 ES metastatic lesions. CNAs were correlated with clinical features and outcome, and validated by immunohistochemistry (IHC). We identified previously reported CNAs, in addition to SMARCB1 (INI1/SNF5) homozygous loss and copy neutral LOH. IHC confirmed SMARCB1 protein loss in 7-10% of clinically diagnosed ES tumors in three separate cohorts (University of Utah [N = 40], Children's Oncology Group [N = 31], and University of Michigan [N = 55]). A multifactor copy number (MCN)-index was highly predictive of overall survival (39% vs. 100%, P < 0.001). We also identified RELN gene deletions unique to 25% of ES metastatic samples. In summary, we identified both known and novel CNAs using MIP technology for the first time in FFPE samples from patients with ES. CNAs detected by microarray correlate with outcome and may be useful for risk stratification in future clinical trials.

SMARCB1 deficiency in tumors from the peripheral nervous system: a link between schwannomas and rhabdoid tumors?

BACKGROUND

Inactivation of SMARCB1 tumor-suppressor gene was originally described as highly specific for rhabdoid tumors (RTs). Nevertheless, recent reports have illustrated that SMARCB1 alterations also characterize other tumors; in particular, some familial schwannomatosis and epithelioid malignant peripheral nerve sheath tumors, both from peripheral nervous system (PNS) origin, lack BAF47 expression. To document the putative role of SMARCB1 in PNS, we reviewed PNS tumors referred to our institution for a molecular analysis of SMARCB1 because of histologic features compatible with RT.

METHODS

Clinicopathologic, radiologic, and molecular characteristics were detailed for the 12 cases showing loss of expression and/or biallelic inactivation of SMARCB1. The status of the NF2 gene, likely to synergize with SMARCB1 in PNS tumors, was also analyzed.

RESULTS

Patients' age ranged from 0 to 45 years (median age, 6.6 y). Neurological symptoms were observed in 7/12 cases with radiologic features evoking a neuroblastic tumor in 6 cases and a peripheral nerve tumor in 4 cases. The mean delay before diagnosis was 3 months. Histologic examination revealed rhabdoid features in 11/12 tumors. All tumors showed a complete loss of SMARCB1 expression. Interestingly, adjacent nervous proliferation resembling neurofibromas were observed in 3 cases, suggesting a multistep transformation. Three tumors harbored a hemizygous deletion at the NF2 locus, but all NF2 sequences were normal.

CONCLUSIONS

We report the first series of PNS RT. In patients with aggressive PNS tumors, RT should be suspected, and anti-SMARCB1 immunohistochemical analysis should be performed. SMARCB1 inactivation, occasionally associated with NF2 deletion, might have oncogenic effects in peripheral nerves.

High-grade carcinomas involving the renal sinus: report of a case and review of the differential diagnosis and immunohistochemical expression

We report the case of a high-grade carcinoma involving the kidney in a young male with renal vein thrombosis and review the differential diagnosis and immunohistochemical workup. High-grade neoplasms involving the renal sinus include collecting duct carcinomas (CDCs), renal medullary carcinomas (RMCs), invasive high-grade urothelial carcinoma (UC) of the upper urinary tract, clear cell renal cell carcinoma, and type 2 papillary renal cell carcinoma. Distinguishing UC from CDC and RMC is problematic in small biopsy samples. The diagnosis of CDC (a rare, aggressive subtype of renal cell carcinoma) is challenging and requires the exclusion of UC. Renal medullary carcinoma is characterized by an appropriate clinical setting and consistent loss of nuclear expression of integrase interactor 1 (INI-1). A panel consisting of p63, paired box gene 8 (PAX8), and INI-1 is most optimal in distinguishing UC from CDC and RMC. A subset of urothelial carcinoma of upper urinary tract may be positive with PAX8.

Interpretation of needle biopsies of the kidney for investigation of renal masses

The development of new therapeutic options for renal tumors has lead to the need of a pretherapeutic diagnosis for an increasing proportion of patients presenting with a renal mass. This need is particularly important for a small, incidentally discovered renal mass (less than 4 cm) as it can be a benign lesion in a significant percentage of cases. Recent studies have shown that needle biopsy is an accurate and safe method allowing for a precise histopathological diagnosis of the mass in most cases. The aims of the biopsy are (1) to assess the benign or malignant nature of the lesion, (2) to assess the primary or secondary nature of the lesion, and (3), in case of a primary malignancy, to determine histological prognostic factors, such as the tumor type. This review, based on the most recent literature and our own experience, is intended to provide a practical approach to the diagnosis, relying on appropriate morphologic assessment and the use of immunohistochemistry.

Soft tissue tumors of uncertain origin

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

Expression of OCT3/4 in renal medullary carcinoma represents a potential diagnostic pitfall

Renal medullary carcinoma (RMC) is a rare aggressive renal tumor that classically afflicts young black patients with sickle cell trait. The tumor shows overlapping pathologic and clinical characteristics with collecting duct carcinoma and urothelial carcinoma, which often results in a diagnostic conundrum. When the tumor presents in a metastatic site in the absence of a history of renal tumor, germ-cell tumor is often a primary diagnostic consideration, given the young age of most patients. OCT3/4 is an immunohistochemical marker that is routinely used in clinical practice and is widely considered to be a specific marker for germ-cell tumor. We studied the pathologic and immunohistochemical characteristics of 14 cases of RMC. Immunohistochemical staining for OCT3/4 staining was noted in 10/14 RMCs with strong nuclear staining in 8 cases and was absent in all cases of collecting duct carcinoma and urothelial carcinoma. OCT3/4 expression is not specific to germ-cell tumor and is seen in the majority of RMC cases. Caution must be exercised in interpreting the presence of OCT3/4 staining in a poorly differentiated neoplasm, especially at a metastatic site as a germ-cell tumor, as this may represent a potential diagnostic pitfall.

Claudin-6 is a nonspecific marker for malignant rhabdoid and other pediatric tumors

Claudins are tight junction proteins with claudin-6 (CLDN6) expression mostly restricted to embryonic and fetal life. Previously reported gene expression microarray analysis showed an increased level of CLDN6 in atypical teratoid rhabdoid tumors (AT/RT) compared with other central nervous system (CNS) tumors and sarcomas. However, there exist conflicting data on expression of CLDN6 as assessed by immunohistochemistry in CNS tumors. We established membranous staining as a specific and reproducible method for evaluating CLDN6 expression based on fetal and adolescent controls. We then evaluated a large group (257) of pediatric tumors using tissue microarrays, including: 47 malignant rhabdoid tumors (MRTs), (31 AT/RTs and 16 non-CNS MRTs); 67 small, round, blue cell tumors (10 Wilms tumors, 10 embryonal rhabdomyosarcomas, 10 neuroblastomas (NBs), 10 synovial sarcomas (SSs), 9 hepatoblastomas (HBs), 9 alveolar rhabdomyosarcomas, and 9 Ewings sarcomas); and 143 CNS tumors (24 medulloblastomas, 21 pilocytic astrocytomas, 14 astrocytomas grade II/III, 13 gangliogliomas, 12 glioblastomas, 12 ependymal tumors, 11 choroid plexus tumors, 10 meningiomas, 8 dysembryoplastic neuroepithelial tumors, 8 oligodendrogliomas, 4 craniopharyngiomas, 2 germinomas, 2 primitive neuroectodermal tumors (PNET), and 2 central neurocytomas). CLDN6 expression was seen in 12 of 31 (39%) AT/RTs, 7 of 16 (44%) non-CNS MRTs, 5 of 10 (50%) Wilms tumors, 1 of 9 (11%) HBs, 2 of 2 (100%) germinomas, 1 of 2 (50%) CNS PNETs, 1 of 24 (4%) medulloblastomas, and 1 of 10 (10%) meningiomas. Ten of 11 (91%) choroid plexus tumors showed apical staining but no concentric membranous staining. Although CLDN6 is expressed in both AT/RTs and MRTs, it is not a specific biomarker as it is expressed in a variety of other pediatric CNS and soft tissue tumors.

p63, CK7, PAX8 and INI-1: an optimal immunohistochemical panel to distinguish poorly differentiated urothelial cell carcinoma from high-grade tumours of the renal collecting system

AIMS

High-grade, poorly differentiated, infiltrative carcinomas involving the renal sinus region often pose challenging differential diagnostic considerations, specifically differentiation of urothelial carcinoma (UC) from renal cell carcinoma (RCC) subtypes. Accurate classification, especially the distinction of UC from RCC, is critical, as therapeutic approaches differ.

METHODS AND RESULTS

Cluster analysis was performed on immunohistochemical data from 18 invasive UCs, six CDCs, two RMCs, 18 type 2 papillary renal cell carcinomas (PRCCs) and 20 high-grade clear cell renal cell carcinomas (CRCCs) using a broad panel of traditional and novel immunohistochemical markers. The initial analysis with all antibodies segregates almost all the RCCs (45 of 46, 98%) from all the UCs based on the lack of expression of p63 in all (100%) RCCs, along with predominant strong expression of paired box gene 8 (PAX8) and vimentin, predominant lack of expression of high molecular weight cytokeratin (HMCK) and CK7 and variable expression of RCC, CD10, CA1X and PAX2. All the UCs cluster together with strong, diffuse reactivity for p63, predominant reactivity for CK7 and high molecular weight kininogen (HMWK), and absent to minimal staining with PAX8, RCC antigen, PAX2, alpha-methylacyl-CoA racemase (AMACR), carbonic anhydrase IX (CAIX) and vimentin. After removing antibodies with significant overlap and/or minimal impact, a second analysis with a limited panel including p63, CK7, vimentin, integrase interactor 1 (INI-1) and PAX8 was performed. Again, the majority of UCs cluster into one group and p63 positivity separates all UCs from RCCs.

CONCLUSIONS

Lack of INI-1 expression, noted exclusively in RMCs, segregates RMCs into a separate cluster. PAX8 is rarely positive (17%) in UC, is commonly expressed in CDC, RMC, PRCC and CRCC and is superior to PAX2.

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.

Epithelioid Lesions

Epithelioid variants have been described for most mesenchymal tumors, including leiomyosarcoma, pleomorphic liposarcoma, epithelioid fibrous histiocytoma, and myxofibrosarcoma. Soft tissue tumors that commonly show epithelioid morphology include epithelioid vascular lesions, epithelioid sarcoma, sclerosing epithelioid fibrosarcoma, and epithelioid malignant peripheral nerve sheath tumor. Many of the entities described in this review were originally described as "simulating carcinoma" or "often mistaken for carcinoma" and this pitfall should be considered when evaluating epithelioid lesions in soft tissue. Many epithelioid soft tissue tumors express epithelial antigens to a varying degree and an immunohistochemical panel is essential for correct classification.

p16INK4A and p14ARF tumor suppressor pathways are deregulated in malignant rhabdoid tumors

Malignant rhabdoid tumors (MRTs) are aggressive tumors associated with mutations in the SMARCB1 gene. In experimental systems, the loss of SMARCB1 is hypothesized to alter p16(INK4A) pathways resulting in the repression of tumor suppressors. To determine whether these pathways are deregulated in human MRT, we used immunohistochemistry on tissue microarrays to evaluate p16(INK4A)/E2F1/RB and p14(ARF)/MDM2/p53 pathways in 25 atypical teratoid/rhabdoid tumors (AT/RT) and 11 non-CNS MRT. p16(INK4A) was negative or showed focal weak expression. p16(INK4A) downstream targets CDK4/cyclin D1/ppRB were variably expressed at moderate to low levels; E2F1 was negative. Unexpectedly, p14(ARF) expression was seen in many cases, which correlated positively with p53 and inversely with MDM2 immunostaining in AT/RT. TP53 mutational analysis in 19 of 25 AT/RT and in 8 of 11 non-CNS MRT cases showed point mutations in only 3 AT/RT cases, suggesting that p53 expression was driven mainly by p14(ARF). Finally, nucleophosmin, a protein that stabilizes p53, was positive in most cases and colocalized with p53. Together, these data suggest that, in MRT, there is deregulation not only of p16(INK4A) but also of the p14(ARF) pathway. These results provide insights into cell cycle deregulation in the pathogenesis of human MRT and may aid in the design and evaluation of potential therapies for these tumors.