Cribriform neuroepithelial tumor: molecular characterization of a SMARCB1‐deficient non‐rhabdoid tumor with favorable long‐term outcome

Rhabdoid phenotype and loss of SMARCB1 expression in a brain tumor are characteristic features of atypical teratoid/rhabdoid tumors (ATRT). Rare non‐rhabdoid brain tumors showing cribriform growth pattern and SMARCB1 loss have been designated cribriform neuroepithelial tumor (CRINET). Small case series suggest that CRINETs may have a relatively favorable prognosis. However, the long‐term outcome is unclear and it remains uncertain whether CRINET represents a distinct entity or a variant of ATRT. Therefore, 10 CRINETs were clinically and molecularly characterized and compared with 10 ATRTs of each of three recently described molecular subgroups (i.e. ATRT‐TYR, ATRT‐SHH and ATRT‐MYC) using Illumina Infinium HumanMethylation450 arrays, FISH, MLPA, and sequencing. Furthermore, outcome was compared to a larger cohort of 27 children with ATRT‐TYR. Median age of the 6 boys and 4 girls harboring a CRINET was 20 months. On histopathological examination, all CRINETs demonstrated a cribriform growth pattern and distinct tyrosinase staining. On unsupervised cluster analysis of methylation data, all CRINETs examined exclusively clustered within the ATRT‐TYR molecular subgroup. As ATRT‐TYR, CRINETs mainly showed large heterozygous 22q deletions (9/10) and SMARCB1 mutations of the other allele. In two patients, SMARCB1 mutations were also present in the germline. Estimated mean overall survival in patients with CRINETs was 125 months (95% confidence interval 100–151 months) as compared to only 53 (33–74) months in patients with ATRTs of the ATRT‐TYR subgroup (Log‐Rank P < 0.05). In conclusion, CRINET represents a SMARCB1‐deficient non‐rhabdoid tumor, which shares molecular similarities with the ATRT‐TYR subgroup but has distinct histopathological features and favorable long‐term outcome.     

Infrequent SMARCB1/INI1 gene alteration in epithelioid sarcoma: a useful tool in distinguishing epithelioid sarcoma from malignant rhabdoid tumor

Loss of SMARCB1/INI1 protein expression is considered useful for confirming a histologic diagnosis of malignant rhabdoid tumor. However, loss of SMARCB1/INI1 protein expression has recently been reported in other tumors as well, including a few cases of epithelioid sarcoma. In addition, the histopathologic differences between proximal-type epithelioid sarcoma and malignant rhabdoid tumor have not been conclusively defined. We analyzed SMARCB1/INI1 protein expression in 54 epithelioid sarcoma (proximal-type, 25; distal-type, 29) and examined alterations of the SMARCB1/INI1 gene in the cases lacking protein expression. We found that 19 (76.0%) proximal-type epithelioid sarcoma and 27 (93.1%) distal-type epithelioid sarcoma showed loss of SMARCB1/INI1 protein expression. Analysis of 39 cases with loss of protein expression revealed 4 cases (10.3%) with SMARCB1/INI1 gene alterations at the DNA level (homozygous deletion, 2; 1- or 2-bp deletion, 2) that could have induced the loss of gene products, and all 4 of these were proximal-type epithelioid sarcoma. Epithelioid sarcoma was thus associated with a high frequency of loss of SMARCB1/INI1 protein expression similar to that in malignant rhabdoid tumor. However, the frequency of SMARCB1/INI1 gene alteration at the DNA level in proximal-type epithelioid sarcoma was significantly lower than that in malignant rhabdoid tumor. In addition, the prognosis of patients with malignant rhabdoid tumor is significantly worse than that of patients with proximal-type epithelioid sarcoma (P = .001). Therefore, proximal-type epithelioid sarcoma and malignant rhabdoid tumor are suggested to be distinctive tumors with respect to the mechanism of the loss of SMARCB1/INI1 protein expression. Analysis of alterations in the SMARCB1/INI1 gene may thus be a useful diagnostic tool to distinguish proximal-type epithelioid sarcoma from malignant rhabdoid tumor.     

Mutation of the INI1 gene in composite rhabdoid tumor of the endometrium

Composite rhabdoid tumors are typically adult tumors that contain a component of rhabdoid cells, which are characteristic of the aggressive childhood malignant rhabdoid tumor. Pediatric rhabdoid tumors are characterized by the inactivation of the hSNF5/INI1/SMARCB1 gene, with subsequent loss of expression of the protein. In contrast, only a single composite rhabdoid tumor has demonstrated involvement of the INI1 gene. In our study, INI1 protein expression was studied in 2 uterine carcinosarcomas with rhabdoid components (composite rhabdoid tumors). The rhabdoid component of 1 tumor showed lack of immunoreactivity for the INI1 protein and strong positivity for cyclin D1, whereas the adenocarcinomatous component of the tumor and both components of the second tumor were immunoreactive for the INI1 protein and negative for cyclin D1. Loss of one INI1 allele and a mutation in exon 7 of the remaining allele were detected in the first tumor, consistent with the immunohistochemistry results. Our results demonstrate that deletions and mutations of the INI1 gene can occur also in rare composite rhabdoid tumors of adulthood. Further studies are necessary, however, to determine the prognostic significance of this finding.     

Congenital anomalies and rhabdoid tumor associated with 22q11 germline deletion and somatic inactivation of the SMARCB1 tumor suppressor

The most common microdeletion in humans involves the 22q11 region. Congenital anomalies associated with 22q11 loss include cardiac and facial defects. Less frequent is the co-presentation of malignant rhabdoid tumors that are highly aggressive childhood malignancies typically found in renal or extra-renal soft tissues and central nervous system. A newborn patient presented with multiple congenital anomalies consistent with 22q11 deletion syndrome including cleft lip and palate, ear tags and ventricular septal defects co-presenting with an axillary rhabdoid tumor. Comparative genomic hybridization revealed a 2.8 Mb germline deletion in the 22q11.2 region containing genes required for normal fetal development and the SMARCB1 tumor suppressor gene. Analysis of tumor DNA revealed a somatic deletion of exon 7 in the second allele of SMARCB1. Expression of SMARCB1 was absent, while tumor markers including MYC, GFAP, and CLAUDIN-6 were upregulated. The presence of tandem oriented BCRL modules located within interspersed low copy repeat elements throughout the 22q11 distal region may predispose this area for microdeletions through nonalleleic homologous recombination.     

Hereditary SWI/SNF complex deficiency syndromes

The SWItch Sucrose non-fermentable (SWI/SNF) complex is a highly conserved multi-subunit complex of proteins encoded by numerous genes mapped to different chromosomal regions. The complex regulates the process of chromatin remodelling and hence plays a central role in the epigenetic regulation of gene expression, cell proliferation and differentiation. During the last three decades, the SWI/SNF complex has been increasingly recognized as a central molecular event driving the initiation and/or progression of several benign and malignant neoplasms of different anatomic origin and having diverse histomorphological appearance. Atypical teratoid/rhabdoid tumors (AT/RT) and renal/extrarenal malignant rhabdoid tumors of childhood, epithelioid sarcoma and small cell carcinoma of the ovary, hypercalcemic type (SCCOHT) represent the most commonly recognized SWI/SNF-driven neoplasms. Approximately one-third of pediatric malignant rhabdoid tumors are linked to germline SWI/SNF alterations (SMARCB1/INI1, rarely SMARCA4) resulting in occasional familial clustering of these highly aggressive malignancies (so-called rhabdoid tumor predisposition syndrome, RTPS, types 1 and 2, respectively). However, more recently, inherited SWI/SNF-deficiency has been linked to several benign syndromic tumors including a subset of familial schwannomatosis (linked to SMARCB1) and multiple meningiomas (linked to SMARCE1) as well as others. Beyond neoplasms, several congenital developmental functional disorders such as Coffin-Siris syndrome and intellectual disability are now known to be SWI/SNF-related. The latter are essentially not associated with SWI/SNF-driven neoplasms, although at least anecdotal cases have documented concurrence of both neoplastic and developmental disorders. This review summarizes the most important SWI/SNF-driven diseases with a main focus on neoplasms.     

SMARCB1/INI1 missense mutation in mucinous carcinoma with rhabdoid features

Malignant rhabdoid tumor (MRT) is a rare and aggressive tumor associated with deletion or mutation of a tumor suppressor gene SMARCB1/INI1, a member of the SWI/SNF chromatin-remodeling complex. Reported herein is a case of pancreatic mucinous carcinoma accompanying rhabdoid features with immunohistochemical and ultrastructural studies as well as analysis of the SMARCB1/INI1 gene. A 65-year-old woman presented with a 2 month history of abdominal and chest pain. A well-defined grayish tan fish-flesh mass (11 x 9 x 7 cm) with focal mucinous area was present in the pancreatic tail. Microscopically, the tumor had a biphasic growth pattern: a mucinous carcinoma component and a poorly differentiated carcinoma component with rhabdoid features showing loosely cohesive cells with abundant eosinophilic cytoplasm, displaced nuclei, and prominent nucleoli. The rhabdoid component coexpressed vimentin and cytokeratin. Sequencing analysis of the DNA extracted from the mucinous and rhabdoid components showed a missense mutation CCC to ACC in codon 116 of the SMARCB1/INI1 gene. Being aware of rhabdoid features would help diagnose this rare and aggressive malignant tumor and may provide an opportunity for further evaluation of SMARCB1/INI1 gene alteration and determination of its prognostic significance.     

Update from the 2011 International Schwannomatosis Workshop: From genetics to diagnostic criteria

Schwannomatosis is the third major form of neurofibromatosis and is characterized by the development of multiple schwannomas in the absence of bilateral vestibular schwannomas. The 2011 Schwannomatosis Update was organized by the Children's Tumor Foundation ( www.ctf.org ) and held in Los Angeles, CA, from June 5–8, 2011. This article summarizes the highlights presented at the Conference and represents the “state‐of‐the‐field” in 2011. Genetic studies indicate that constitutional mutations in the SMARCB1 tumor suppressor gene occur in 40–50% of familial cases and in 8–10% of sporadic cases of schwannomatosis. Tumorigenesis is thought to occur through a four‐hit, three‐step model, beginning with a germline mutation in SMARCB1 (hit 1), followed by loss of a portion of chromosome 22 that contains the second SMARCB1 allele and one NF2 allele (hits 2 and 3), followed by mutation of the remaining wild‐type NF2 allele (hit 4). Insights from research on HIV and pediatric rhabdoid tumors have shed light on potential molecular pathways that are dysregulated in schwannomatosis‐related schwannomas. Mouse models of schwannomatosis have been developed and promise to further expand our understanding of tumorigenesis and the tumor microenvironment. Clinical reports have described the occurrence of intracranial meningiomas in schwannomatosis patients and in families with germline SMARCB1 mutations. The authors propose updated diagnostic criteria to incorporate new clinical and genetic findings since 2005. In the next 5 years, the authors expect that advances in basic research in the pathogenesis of schwannomatosis will lead toward clinical investigations of potential drug therapies. © 2013 Wiley Periodicals, Inc.     

Rhabdoid Tumors: An Initial Clue to the Role of Chromatin Remodeling in Cancer

The discovery of biallelic, inactivating SMARCB1 mutations in rhabdoid tumors (RTs) over a decade ago represented the first recognized link between chromatin remodeling and tumor suppression. SMARCB1 is a core subunit of the SWI/SNF chromatin remodeling complex, and the recent emergence of frequent mutations in genes that encode subunits of this complex across a wide variety of cancers suggests that perturbation of this chromatin remodeling complex constitutes a key driver of cancer formation. Despite the highly aggressive nature of RTs, they are genetically simple cancers that appear to lack chromosomal instability and contain very few mutations. Indeed, the mutation rate in RTs is among the lowest of all cancers sequenced, with loss of SMARCB1 as essentially the sole recurrent event. Given the genetic simplicity of this disease, understanding the chromatin dysregulation caused by SMARCB1 loss may provide more general insight into how epigenetic alterations can contribute to oncogenic transformation and may reveal opportunities for targeted therapy not only of RT but also the variety of other SWI/SNF mutant cancers.     

Translocation (1;22)(p36;q11.2) with concurrent del(22)(q11.2) resulted in homozygous deletion of <Emphasis Type="Italic">SNF5/INI1</Emphasis> in a newly established cell line derived from extrarenal rhabdoid tumor

Malignant rhabdoid tumor (MRT) is a highly malignant pediatric cancer, which arises in various sites such as the kidney, brain, and soft tissues. Cytogenetic studies have revealed alterations of 22q11 in MRT. Recently, deletions and mutations of the SNF5/INI1 locus in 22q11.2 have been reported in MRT, suggesting that SNF5/INI1 is a tumor suppressor gene for MRT. Here we report our molecular cytogenetic study for a newly established cell line from extrarenal MRT with t(1;22)(p36;q11.2). Consequently, the reciprocal translocation was associated with the interstitial deletion of a small segment including SNF5/INI1, and another, chromosome 22, showed terminal deletion, the breakpoint of which was located 70–80 kb centromeric to SNF5/INI1, resulting in homozygous deletion of SNF5/INI1 in this cell line.     

Infant brain tumors: a neuropathologic population-based institutional reappraisal

The factors that impact the long-term functional outcome for infants with brain tumor are unclear. The clinicopathologic features of all infant brain tumors occurring at our institution (1982-2005) were reexamined to explore the factors influencing prognosis. The details of the neuropathologic review are reported herein. Thirty-five cases were identified and included 7 astrocytomas (6 low grade and 1 glioblastoma), 6 atypical teratoid rhabdoid tumors, 5 choroid plexus papillomas, 4 ependymomas (3 anaplastic), 4 teratomas (3 immature), 2 supratentorial primitive neuroectodermal tumors, 2 gangliogliomas, 2 desmoplastic tumors of infancy, and 1 each of "medulloblastoma with extensive nodularity," adamantinomatous craniopharyngioma, and 1 "malignancy not otherwise specified." The original diagnosis was changed in 8 cases (23%), and atypical teratoid rhabdoid tumors was the most common revision (n = 5). Case 9 was unusual in that both the patient and her 2-year-old sister displayed INI-1 immunonegative posterior fossa tumors and extended survival. Tumor grade was altered in 6 cases (17%), the most significant instance being the downgrading from the World Health Organization grade IV to I (case 18: supratentorial primitive neuroectodermal tumors to desmoplastic tumors of infancy). As opposed to other reports in the literature, our cohort contained a substantially higher frequency of atypical teratoid rhabdoid tumors and a lower frequency of medulloblastoma. Changes in the histologic diagnosis/grade in a significant subset of cases most likely reflect the continual evolution of brain tumor classification schemes. INI-1 immunohistochemistry was instrumental in the pathologic assessment of select cases and raised the possibility that atypical teratoid rhabdoid tumors may be the most common infant brain malignancy.     

Molecularly confirmed primary malignant rhabdoid tumor of the urinary bladder: implications of accurate diagnosis

Malignant rhabdoid tumors (MRTs) are well recognized in the kidney and extrarenal sites such as soft tissues, retroperitoneum, and bladder but are classified as atypical teratoid/rhabdoid tumors in the central nervous system. The unifying features of both extracranial MRT and atypical teratoid/rhabdoid tumors are the exon deletions/mutations of the SMARCB1 (SWI/SNF related, matrix associated, actin dependent regulator of chromatin, subfamily b, member 1) gene in 22q11.23 and resulting loss of SMARCB1/INI1 (integrase interactor 1) protein expression by immunohistochemistry. We herein report a case of extrarenal rhabdoid tumor confined to the bladder in a 3-year-old child, diagnosed by histopathology and confirmed by immunohistochemical and molecular studies. This is only the fourth molecularly proven primary MRT of the bladder to be reported. The patient's peripheral blood was negative for the deletions observed in the tumor, thereby confirming a sporadic origin for the tumor. Given the possible dismal outcome, urgency for definitive diagnosis to institute intensive multimodality therapy, histopathologic differential diagnosis with rhabdomyosarcoma and urothelial carcinoma with rhabdoid features, and lack of consensus management guidelines, oncologists, urologists, and pathologists must be aware of this entity. Evaluation for a germ line SMARCB1 alteration may greatly aid risk stratification and family planning.     

Germline INI1 mutation in a patient with a central nervous system atypical teratoid tumor and renal rhabdoid tumor

We describe a four-month-old child who presented with an atypical teratoid/rhabdoid tumor of the brain and subsequently developed a renal rhabdoid tumor. Distinct histologic features, immunophenotypic profiles, and deletions of chromosome 22 were supportive of two primary tumors. An identical mutation in exon 7 of the INI1 rhabdoid tumor suppressor gene was identified in both tumors, as well as in normal kidney tissue. We propose that this germline INI1 mutation predisposed the child to the development of both malignancies. These findings lend support to the hypothesis that rhabdoid tumors in all sites have a common genetic etiology.     

SWI/SNF-deficient neoplasms of the genitourinary tract

Since the discovery of association of SMARCB1 mutations with malignant rhabdoid tumors and renal medullary carcinoma, mutations in genes of the SWI/SNF chromatin remodeling complex have been increasingly identified across a diverse spectrum of neoplasms. As a group, SWI/SNF complex subunit mutations are now recognized to be the second most frequent type of mutations across tumors. SMARCB1 mutations were originally reported in malignant rhabdoid tumors of the kidney and thought to be pathognomonic for this tumor. However, more broadly, recognition of typical rhabdoid cytomorphology and SMARCB1 mutations beyond rhabdoid tumors has changed our understanding of the pathobiology of these tumors. While mutations of SWI/SNF complex are diagnostic of rhabdoid tumors and renal medullary carcinoma, their clinical relevance extends to potential prognostic and predictive utility in other tumors as well. Beyond SMARCB1, the PBRM1 and ARID1A genes are the most frequently altered members of the SWI/SNF complex in genitourinary neoplasms, especially in clear cell renal cell carcinoma and urothelial carcinoma. In this review, we provide an overview of alterations in the SWI/SNF complex encountered in genitourinary neoplasms and discuss their increasing clinical importance.     

Type 1 papillary renal cell carcinoma in a patient with schwannomatosis: Mosaic versus loss of SMARCB1 expression in respectively schwannoma and renal tumor cells

In schwannomatosis, germline SMARCB1 or LZTR1 mutations predispose to the development of multiple benign schwannomas. Besides these, other tumors may occur in schwannomatosis patients. We present a 45‐year‐old male patient who developed multiple schwannomas and in addition a malignant type 1 papillary renal cell carcinoma (pRCC1). We identified a duplication of exon 7 of SMARCB1 on chromosome 22 in the constitutional DNA of the patient (c.796‐2246_986 + 5250dup7686), resulting in the generation of a premature stop codon in the second exon 7 copy (p.Glu330*). The mutant SMARCB1 allele proved to be retained in three schwannomas and in the pRCC1 of the patient. Loss of heterozygosity analysis demonstrated partial loss of the wild‐type SMARCB1 allele containing chromosome 22, suggesting loss of that chromosome in only a subset of tumor cells, in all four tumors. Immunohistochemical staining with a SMARCB1 antibody revealed a mosaic SMARCB1 expression pattern in the three benign schwannomas, but absence of expression in the malignant tumor cells of the pRCC1. To our knowledge, this difference in SMARCB1 protein expression has not been reported before. We conclude that a germline SMARCB1 mutation may predispose to the development of pRCC1, thereby further widening the spectrum of tumors that can develop in the context of schwannomatosis. © 2016 Wiley Periodicals, Inc.     

Small cell undifferentiated (SCUD) hepatoblastomas: All malignant rhabdoid tumors?

Small cell undifferentiated (SCUD) hepatoblastoma is a rare variant of hepatoblastoma with poor outcome and loss of INI1 expression, sharing this with malignant rhabdoid tumors (MRT). We studied all tumors from the files of the Kiel Pediatric Tumor Registry (KTR) with the initial diagnosis of SCUD and MRT. After re‐review, we performed immunistochemistry, fluorescence in situ hybridization, and multiplex ligation dependent probe amplification for loss of expression and deletion of INI1/SMARCB1 in 23 tumors. Morphologically, 12 of the tumors had a small cell morphology, 9 showed the typical picture of MRT, and 2 were composed of both small cells and rhabdoid cells. All but 1 of the 23 tumors showed loss of INI1 protein expression by immunohistochemistry. Nineteen of the INI1 negative tumors were analyzed by FISH technique and all showed a deletion of the INI1/SMARCB1 gene (17 homozygous deletions, 2 heterozygous deletions). We investigated 14 of these cases by multiplex ligation dependent probe amplification and verified the deletions in all cases. In conclusion, we postulate that SCUD hepatoblastoma is not a hepatoblastoma but represents a malignant rhabdoid tumor of the liver. © 2016 Wiley Periodicals, Inc.     

Epidermal growth factor receptor abnormalities in atypical teratoid/rhabdoid tumors and an unusual case with gene amplification

Atypical teratoid/rhabdoid tumor (AT/RT) is a rhabdoid tumor of the central nervous system comprising a mixture of small round cells and mesenchymal and/or epithelial elements, showing mutation of the SMARCB1 gene or SMARCA4 gene. The epidermal growth factor receptor (EGFR) is one of the tyrosine kinase receptors whose overexpressed protein plays important roles in the malignant characteristics of various tumors. We analyzed 8 Japanese cases of AT/RT for EGFR protein overexpression and egfr gene amplification using immunohistochemistry and fluorescence in situ hybridization. The patients included 7 boys and 1 girl (age range 13 days to 2 years), and the tumors were localized in the frontal lobe (1 case), lateral ventricle (1 case), third ventricle (1 case), fourth ventricle (3 cases), and cerebellum (2 cases). We found that all (100%) of them partially expressed a high level of EGFR protein, and that one case showed amplification of egfr, the amplified area being localized and limited to a specific area within the tumor. We speculate that AT/RT is a tumor with heterogeneous egfr amplification, and that the frequency of amplification may depend on loss of function of the specific chromatin-remodeling member.     

Diagnosis of distal 22q11.2 deletion syndrome in a patient with a teratoid/rhabdoid tumour

We report an 18 year old patient with mild intellectual disability who was diagnosed with a late onset teratoid/rhabdoid tumour by histological and immunohistochemical studies. Array-CGH studies, performed on a peripheral blood sample, showed a 3.4Mb deletion of chromosome 22q11.2, distal to the common DiGeorge syndrome (DGS) or Velocardiofacial syndrome (VCFs) region. This deletion is consistent with a diagnosis of distal 22q11.2 deletion syndrome. The deletion encompasses the INI1/SMARCB1 tumour suppressor gene. Biallelic inactivation of this gene is characteristic of atypical teratoid/rhabdoid tumours. Although several constitutional chromosome conditions are known to have increased susceptibility to various forms of cancer, very little is known regarding the magnitude of risk for malignancy associated with distal 22q11.2 deletion syndrome. In view of this finding we suggest that patients diagnosed with distal 22q11.2 deletion syndrome undergo careful prolonged monitoring for this type of tumour. This case demonstrates the need to carefully assess regions found to be deleted in individuals, referred for dysmorphia and/or developments delay, by array-CGH for the presence of genes known to be implicated in malignancy.     

A case of renal cell carcinoma unclassified with medullary phenotype without detectable gene deletion

Renal cell carcinoma unclassified with medullary phenotype (RCCU‐MP) is a rare variant of renal medullary carcinoma (RMC) characterized by loss of SMARCB1 (INI1 / SNF5 / BAF47) protein expression in patients without sickle cell trait. Here, we report a case of RCCU‐MP in a Japanese patient who had experienced colon cancer 13 years ago, gastric cancer 11 years ago and lung cancer 9 years ago and had received hemodialysis for 15 years. This is the first report of RCCU‐MP in Japan. The patient was not of African descent, and did not have SCT or any other hereditary blood abnormality typical of RMC. The tumor was located in the left kidney, and was composed histologically of rhabdoid cells with marked lymphocyte infiltration; it was immunohistochemically negative for SMARCB1. We were, however, unable to detect mutation in the SMARCB1 gene, reduced messengerRNA expression, or deletion or translocation of chromosome 22, where the SMARCB1 gene is located. These results suggest that RCCU‐MP may not involve the hemizygous loss of this gene noted in typical RMC cases.     

Absence of expression of SMARCB1/INI1 in malignant rhabdoid tumors of the central nervous system, kidneys and soft tissue: an immunohistochemical study with implications for diagnosis.

Malignant rhabdoid tumors are high-grade neoplasms of the central nervous system (CNS), kidneys and soft tissue that usually occur in children. The histologic diagnosis of malignant rhabdoid tumor depends on identification of characteristic rhabdoid cells-large cells with eccentrically located nuclei and abundant, eosinophilic cytoplasm-and immunohistochemistry with antibodies to vimentin, keratin and epithelial membrane antigen. In most malignant rhabdoid tumors, the SMARCB1/INI1 gene, located in chromosome band 22q11.2, is inactivated by deletions and/or mutations, so genetic diagnosis is often possible. However, tissue may not be available for genetic analysis or studies not confirmatory. We assessed SMARCB1/INI1 expression in 17 rhabdoid tumors and 57 other tumors of the CNS, kidney or soft tissue using immunohistochemistry. In total, 12 brain, three renal and two soft tissue rhabdoid tumors were examined along with four glioblastomas, four pilocytic astrocytomas, four oligodendrogliomas, two ependymomas, two choroid plexus papillomas, five pituitary adenomas, four germinomas, four renal carcinomas with Xp11.2 translocations, two clear cell sarcomas, two Wilms' tumors, one renal medullary carcinoma, two desmoplastic small round cell tumors, two alveolar rhabdomyosarcomas, two embryonal rhabdomyosarcomas, one low-grade chondrosarcoma, two extraskeletal myxoid chondrosarcomas, one mesenchymal chondrosarcoma, four malignant peripheral nerve sheath tumors, five metastatic carcinomas and four epithelioid sarcomas, two primary and two metastatic. The neoplastic cells of all rhabdoid tumors, the four epithelioid sarcomas and the renal medullary carcinoma did not express SMARCB1/INI1 by immunohistochemistry; neoplastic cells of all other tumors expressed SMARCB1/INI1. Immunohistochemistry to assess expression of SMARCB1/INI1 may be useful in the diagnosis of rhabdoid tumors of the CNS, kidneys and soft tissue.     

SMARCB1 expression in epithelioid sarcoma is regulated by miR‐206, miR‐381, and miR‐671‐5p on Both mRNA and protein levels

Proximal type epithelioid sarcoma shares similarities with malignant rhabdoid tumor, including the lack of nuclear immunoreactivity of SMARCB1. Biallelic mutation of SMARCB1 has been convincingly established as the cause of loss of protein expression in rhabdoid tumor, but the cause in epithelioid sarcoma remains unknown. In our previous work, we demonstrated that DNA hypermethylation and post‐translational modification mechanisms were not involved. In this current work, we explored the hypothesis that miRNAs regulate SMARCB1 gene expression in epithelioid sarcomas. In silico target prediction analysis revealed eight candidate miRNAs, and quantitative PCR—in 32 formalin‐fixed, paraffin‐embedded tumor samples comprising 30 epithelioid sarcomas and two malignant rhabdoid tumors—demonstrated significant (P < 0.001) overexpression of four miRNAs in epithelioid sarcomas: miR‐206, miR‐381, miR‐671‐5p, and miR‐765. Two human tumors (fibrosarcoma and colon adenocarcinoma) and a normal cell line (human dermal fibroblast) with retained SMARCB1 expression were cultured for miRNA transient transfection (electroporation) experiments. SMARCB1 mRNA expression was analyzed by quantitative real‐time PCR and immunostaining of SMARCB1 was performed to examine the effect of miRNAs transfections on both RNA and protein levels. Only three of the overexpressed miRNAs (miR‐206, miR‐381, and miR‐671‐5p) could silence the SMARCB1 mRNA expression in cell cultures; most effectively miR‐206. Transfection of miR‐206, miR‐381, miR‐671‐5p, and some combination of them also eliminated SMARCB1 nuclear staining, demonstrating a strong effect on not only mRNA but also protein levels. Our results suggest loss of SMARCB1 protein expression in epithelioid sarcoma is due to the epigenetic mechanism of gene silencing by oncomiRs. © 2013 Wiley Periodicals, Inc.