Detection of SS18-SSX fusion transcripts in formalin-fixed paraffin-embedded neoplasms: analysis of conventional RT-PCR, qRT-PCR and dual color FISH as diagnostic tools for synovial sarcoma

Novel Application of Loop-mediated Isothermal Amplification for Rapid Detection of Gene Translocation

Identification of fusion genes in cancer is essential for pathological diagnosis and clinical therapy. Although methods for detection of fusion genes, such as fluorescence in situ hybridization (FISH) and real-time polymerase chain reaction (PCR), have been developed in last two decades, these methods are not ideal for detection of these genetic alterations owing to their high cost and time-consuming procedures. In this study, we developed novel application for detection of gene translocations using loop-mediated isothermal amplification (LAMP). We verified the amplified DNA products of echinoderm microtubule-associated protein-like 4 and anaplastic lymphoma kinase (EML4-ALK), synaptotagmin and synovial sarcoma, X breakpoint (SYT-SSX), and immunoglobulin heavy chain gene and B cell leukemia/lymphoma 2 (IgH/BCL2) by real-time PCR, agarose-gel electrophoresis, and the naked eye after the LAMP procedure. Fusion genes were detected in samples diluted 103 times within 60 min. Because of the advantages of rapid amplification, simple operation, and easy detection without requiring sophisticated equipment or technical skill, LAMP may have potential applications as an on-site analytical approach in hospitals for pathological diagnosis and decision making regarding appropriate therapeutic approachs.

ATR Is a Therapeutic Target in Synovial Sarcoma

Synovial sarcoma (SS) is an aggressive soft-tissue malignancy characterized by expression of SS18-SSX fusions, where treatment options are limited. To identify therapeutically actionable genetic dependencies in SS, we performed a series of parallel, high-throughput small interfering RNA (siRNA) screens and compared genetic dependencies in SS tumor cells with those in >130 non-SS tumor cell lines. This approach revealed a reliance of SS tumor cells upon the DNA damage response serine/threonine protein kinase ATR. Clinical ATR inhibitors (ATRi) elicited a synthetic lethal effect in SS tumor cells and impaired growth of SS patient-derived xenografts. Oncogenic SS18-SSX family fusion genes are known to alter the composition of the BAF chromatin-remodeling complex, causing ejection and degradation of wild-type SS18 and the tumor suppressor SMARCB1. Expression of oncogenic SS18-SSX fusion proteins caused profound ATRi sensitivity and a reduction in SS18 and SMARCB1 protein levels, but an SSX18-SSX1 Δ71-78 fusion containing a C-terminal deletion did not. ATRi sensitivity in SS was characterized by an increase in biomarkers of replication fork stress (increased γH2AX, decreased replication fork speed, and increased R-loops), an apoptotic response, and a dependence upon cyclin E expression. Combinations of cisplatin or PARP inhibitors enhanced the antitumor cell effect of ATRi, suggesting that either single-agent ATRi or combination therapy involving ATRi might be further assessed as candidate approaches for SS treatment. Cancer Res; 77(24); 7014-26. ©2017 AACR.

Synovial Sarcoma of Peripheral Nerves: Analysis of 15 Cases

Synovial sarcoma of peripheral nerve (SSPN) is rare with only 26 cases reported in English. SSPN is often mistaken for a benign or malignant peripheral nerve sheath tumor (PNST) by clinicians and pathologists. Fifteen cases of SSPN were retrieved from the pathology files of 3 institutions. All tumors arose in a nerve based on imaging and/or operative findings and the diagnoses were histologically confirmed. Neuropathic symptoms predominated in 11 women and 4 men, 19- to 62-year-old (median, 39 years) with tumors involving the ulnar (5), median (3), peroneal (3) or sciatic (2) nerve, or the L4 or T1 nerve root (2). Tumor sizes ranged from 2 to 13 cm (median, 3.8 cm). The leading clinical diagnosis was PNST (9). Treatment was surgical (14) supplemented with radiation therapy (8) and chemotherapy (6). Fourteen tumors were monophasic and 1 was biphasic; 4 had poorly differentiated (PD) foci (1 rhabdoid). Diagnoses in 12 cases were verified by fluorescence in situ hybridization, reverse transcription polymerase chain reaction or both methods. Follow-up in 14 patients (median, 32 mo) revealed that 2/4 patients with PD tumors died with pulmonary metastases; another was alive with no current evidence of disease (NED) following 2 local recurrences, while the fourth had NED. In contrast, 9/10 patients without PD tumors were alive (7 NED) and 1 died at 12 months with pulmonary infiltrates. SSPN is under-recognized clinically and histologically as it mimics benign and malignant PNST. Molecular analysis is recommended to confirm the diagnosis. PD foci, including rhabdoid areas, may portend a worse outcome, similar to non-neural-based tumors.

H3F3A (Histone 3.3) G34W Immunohistochemistry: A Reliable Marker Defining Benign and Malignant Giant Cell Tumor of Bone

Giant cell tumor of bone (GCTB) is a locally aggressive subarticular tumor. Having recently reported that H3.3 G34W mutations are characteristic of this tumor type, we have now investigated the sensitivity and specificity of the anti-histone H3.3 G34W rabbit monoclonal antibody in a wide variety of tumors including histologic mimics of GCTB to assess its value as a diagnostic marker. We also determined the incidence of H3.3 G34 mutations in primary malignant bone tumors as assessed by genotype and H3.3 G34W immunostaining. A total of 3163 tumors were tested. Totally, 213/235 GCTB (90.6%) showed nuclear H3.3 p.G34W immunoreactivity. This was not the case for the rare variants, p.G34L, M, and V, which occurred most commonly in the small bones of the hands, patella, and the axial skeleton. If these sites were excluded from the analysis, H3.3 G34W expression was found in 97.8% of GCTB. Malignant bone tumors initially classified as osteosarcomas were the only other lesions (n=11) that showed G34W expression. Notably an additional 2 previously reported osteosarcomas with a p.G34R mutation were not immunoreactive for the antibody. A total of 11/13 of these malignant H3.3-mutant tumors exhibited an osteoclast-rich component: when imaging was available all but one presented at a subarticular site. We propose that subarticular primary malignant bone sarcoma with H3.3 mutations represent true malignant GCTB, even in the absence of a benign GCTB component.

Transducer-like Enhancer of Split 1 as a Novel Immuno- histochemical Marker for Diagnosis of Synovial Sarcoma

BACKGROUND

Synovial sarcoma is a mesenchymal neoplasm that accounts for around 10% of all soft tissue sarcomas. The diagnosis of synovial sarcoma can be a challenging task, particularly with small biopsy specimens.

AIM

We investigated transducer-like enhancer of split 1 (TLE1), monoclonal antibody, expression by immunohistochemical analysis in a group of 74 synovial sarcoma cases, 20 cases of MPNST, 12 cases of neurofibroma, 15 cases of schwannoma, 5 cases of MFH, 10 cases of lieomyosarcoma and 10 cases of solitary fibrous tumor.

MATERIALS AND METHODS

Whole tissue sections were examined: (39 biphasic and 35 monophasic). Nuclear immunoreactivity was scored as negative (<5% of cells positive), 1+(mild /5-25%), 2+ (moderate/25-50%), and 3+ (strong >50%).

RESULTS

Overall, 71 (96%) of 74 synovial sarcomas were positive for TLE1, including 37 biphasic (95%) and 34 monophasic (97%) tumors. Other spindle cell tumors showed very low or absent staining of TLE1.

CONCLUSIONS

We conclude that TLE1 is a sensitive marker and can be a useful diagnostic marker for synovial sarcoma, particularly the monophasic forms.

Primary pleuropulmonary and mediastinal synovial sarcoma: a clinicopathologic and molecular study of 26 genetically confirmed cases in the largest institution of southwest China

BACKGROUND

Primary pleuropulmonary and mediastinal synovial sarcomas (PPMSSs) are extremely rare. The authors present the largest series in an Asian population.

METHODS

Between 2000 and 2015, 26 genetically confirmed PPMSSs were included. The clinicopathologic features of all of the cases were reviewed. Immunohistochemical staining was carried out using the following antibodies: TLE1, cytokeratin (AE1/AE3), EMA, CD99, Bcl-2, CK7, CD34, S-100 protein, and Ki-67. The chromosomal translocation t(X;18)(p11.2;q11.2) was detected by fluorescence in situ hybridization (FISH) and reverse transcription polymerase chain reaction (RT-PCR). We compared the clinical, pathologic, immunohistochemical, and molecular features of this series with that of the previous series and soft tissue synovial sarcomas.

RESULTS

This series included 17 males and nine females. The median age was 36.5 years (range, 16-72 years). The tumors involved the lung (76.9 %), pleura (15.4 %), and mediastinum (7.7 %). The median tumor size was 6 cm (range 2.3 ~ 24 cm). The majority of the tumors were well-circumscribed. The tumors were classified as monophasic (84.6 %), biphasic (3.8 %), and poorly differentiated (11.5 %) types. The tumors were graded as French Federation of Cancer Centers (FNCLCC) grade 2 (62.5 %) and FNCLCC 3 (37.5 %). Diffuse immunostaining for TLE1, BCL-2, and CD99 was identified in 91.7, 95.7, and 56.0 % of the tumors, respectively. Focal positivity was seen with EMA (84.6 %), CK7 (55.6 %), cytokeratin (AE1/AE3) (68.0 %), CD34 (5.0 %), and S-100 protein (21.7 %). A high Ki-67 index (≥10 %) was observed in 91.3 % of the tumors. The fusion transcripts included SS18-SSX1 (15/22, 68.2 %), SS18-SSX2 including variants (6/22, 27.3 %), and SS18-SSX4 (1/22, 4.5 %) fusions. The remaining four cases showed positivity for SS18 rearrangement by FISH. Surgical excision of tumors or lobectomy were performed in 20 patients, and seven of the patients underwent adjuvant therapy. Clinical follow-up was available in 73.1 % cases, with a median follow-up of 12.0 months. The median survival time was 14.5 months. Tumor resection (p = 0.024) and no residual tumor (p = 0.004) were associated with an improved overall survival time.

CONCLUSIONS

PPMSS is a highly aggressive neoplasm. Extensive surgical resection of the tumor and more effective adjuvant therapy should be advocated. PPMSS must be differentiated from similar diseases.

The H3F3 K36M mutant antibody is a sensitive and specific marker for the diagnosis of chondroblastoma

AIMS

We recently reported that 95% of chondroblastomas harbour a p.K36M mutation in either H3F3A (chromosome 1) or H3F3B (chromosome 17), with the majority involving H3F3B. The aim of this study was to assess the expression of the K36M-mutated protein by immunohistochemistry in a large group of tumours.

METHODS AND RESULTS

One thousand eight hundred and ninety-four tumours, including 85 chondroblastomas and 10 clear-cell chondrosarcomas, were studied; of these, 82 chondroblastomas and one clear-cell chondrosarcoma known to harbour the H3F3 p.K36M mutation expressed the mutated protein. Three chondroblastomas and nine clear-cell chondrosarcomas wild type for H3F3A/H3F3B were negative for p.K36M immunoexpression. The remaining 1799 cases tested, 545 of which were known to be wild type for the H3F3A and H3F3B p.K36M mutations, included 1047 primary bone tumours, and 507 soft tissue and joint tumours. Two hundred and forty-five other tumour types not expected to harbour the mutation were negative for p.K36M immunoexpression.

CONCLUSIONS

Our data demonstrate the specificity and sensitivity of this immunomarker, and will be a useful adjunct for reaching a diagnosis of chondroblastoma.

Synovial Sarcoma Microvesicles Harbor the SYT-SSX Fusion Gene Transcript: Comparison of Different Methods of Detection and Implications in Biomarker Research

Background. Synovial sarcoma is an aggressive soft-tissue malignancy. This study examines the presence of the SYT-SSX fusion transcript in synovial sarcoma microvesicles as well as its potential role as a biomarker for synovial sarcoma. Patients and Methods. Microvesicle release of synovial sarcoma cells was examined by transmission electron microscopy. RNA-content was analyzed by qPCR, nested PCR, nested qPCR, and droplet digital PCR to compare their sensitivity for detection of the SYT-SSX fusion gene transcript. Whole blood RNA, RNA of mononuclear cells, and microvesicle RNA of synovial sarcoma patients were analyzed for the presence of the fusion gene transcripts. Results. Electron microscopic analysis revealed synovial sarcoma cells releasing membrane-enclosed microvesicles. In vitro, the SYT-SSX fusion gene transcript was detected in both synovial sarcoma cells and microvesicles. Nested qPCR proved to be the most sensitive in detecting the SYT-SSX fusion gene mRNA. In contrast, the fusion gene transcript was not detected in peripheral blood cells and microvesicles of synovial sarcoma patients. Conclusion. Synovial sarcoma cells release microvesicles harboring the SYT-SSX fusion transcript. Nested qPCR proved to be the most sensitive in detecting the SYT-SSX fusion gene mRNA; however, more sensitive assays are needed to detect cancer-specific microvesicles in the peripheral blood of cancer patients.

The impact of chromosomal translocation locus and fusion oncogene coding sequence in synovial sarcomagenesis

Synovial sarcomas are aggressive soft-tissue malignancies that express chromosomal translocation-generated fusion genes, SS18-SSX1 or SS18-SSX2 in most cases. Here, we report a mouse sarcoma model expressing SS18-SSX1, complementing our prior model expressing SS18-SSX2. Exome sequencing identified no recurrent secondary mutations in tumors of either genotype. Most of the few mutations identified in single tumors were present in genes that were minimally or not expressed in any of the tumors. Chromosome 6, either entirely or around the fusion gene expression locus, demonstrated a copy number gain in a majority of tumors of both genotypes. Thus, by fusion oncogene coding sequence alone, SS18-SSX1 and SS18-SSX2 can each drive comparable synovial sarcomagenesis, independent from other genetic drivers. SS18-SSX1 and SS18-SSX2 tumor transcriptomes demonstrated very few consistent differences overall. In direct tumorigenesis comparisons, SS18-SSX2 was slightly more sarcomagenic than SS18-SSX1, but equivalent in its generation of biphasic histologic features. Meta-analysis of human synovial sarcoma patient series identified two tumor-gentoype-phenotype correlations that were not modeled by the mice, namely a scarcity of male hosts and biphasic histologic features among SS18-SSX2 tumors. Re-analysis of human SS18-SSX1 and SS18-SSX2 tumor transcriptomes demonstrated very few consistent differences, but highlighted increased native SSX2 expression in SS18-SSX1 tumors. This suggests that the translocated locus may drive genotype-phenotype differences more than the coding sequence of the fusion gene created. Two possible roles for native SSX2 in synovial sarcomagenesis are explored. Thus, even specific partial failures of mouse genetic modeling can be instructive to human tumor biology.

Identification of potential mutations and genomic alterations in the epithelial and spindle cell components of biphasic synovial sarcomas using a human exome SNP chip

Background

Synovial sarcoma (SS) is one of the most aggressive soft-tissue sarcomas and is noted for late local recurrence and metastasis. It is of uncertain histological origin and exhibits a biphasic histopathological form involving both the mesenchyme and epithelium. Thus, its diagnosis and therapy remain a huge challenge for clinicians and pathologists. This study aimed to determine whether differential morphological-associated genomic changes could aid in ascertaining the histogenesis of SS and to determine whether these sarcomas showed some specific mutated genes between epithelial and spindle cells that would promote tumor invasion and metastasis.

Methods

We conducted a comprehensive genomic analysis of mesenchymal and epithelial components in 12 formalin-fixed paraffin-embedded biphasic SS samples using the Illumina human exon microarray. Exome capture sequencing was performed to validate the single nucleotide polymorphism (SNP)-chip data, and de novo data were generated using a whole-exome chip with the Illumina exon microarray. Fisher’s exact test based on PLINK analysis of the SNP-chip data.

Results

Here, the SNP-chip data showed that 336 SNPs had association P-values of less than 0.05 by chi-square test. We identified 23 significantly mutated genes between epithelial and spindle cell regions of SSs. Fifteen gene mutations were specific for the spindle cell component (65.2 %) and eight for the epithelial cell component (34.8 %). Most of these genes have not been previously reported in SS, and neuroguidin (NGDN), RAS protein activator like 3 (RASAL3), KLHL34 and MUM1L1 have not previously been linked to cancer; only one gene (EP300) has been reported in SS. Genomic analyses suggested that the differential SNPs in genes used for functional enrichment are mainly related to the inflammatory response pathway, adhesion, ECM–receptor interactions, TGF-β signaling, JAK–STAT signaling, phenylalanine metabolism, the intrinsic pathway and formation of fibrin.

Conclusions

This study investigated novel biological markers and tumorigenic pathways that would greatly improve therapeutic strategies for SS. The identified pathways may be closely correlated with the pathogenic mechanisms underlying SS, and SS development is associated with morphological features.

Electronic supplementary material

The online version of this article (doi:10.1186/s12920-015-0144-7) contains supplementary material, which is available to authorized users.

The diagnostic utility of reduced immunohistochemical expression of SMARCB1 in synovial sarcomas: a validation study

Synovial sarcoma is a malignant mesenchymal neoplasm of uncertain histogenesis, characterized by a specific SS18-SSX fusion. The diagnosis of synovial sarcoma can be challenging based on morphology and conventional immunohistochemistry alone, and identification of the fusion gene by molecular genetics may be necessary for diagnosis. Several recent studies have demonstrated the diagnostic utility of the reduced expression of SMARCB1 in synovial sarcomas as measured using immunohistochemistry. Therefore, we undertook a validation study using synovial sarcomas and other spindle or round cell tumors that could enter differential diagnosis of monophasic or poorly differentiated synovial sarcomas. Among 36 synovial sarcomas that were successfully evaluated, the expression of SMARCB1 was diffusely reduced in 33 cases (92%) at variable degrees. In contrast, the expression of SMARCB1 was not reduced in any of the 93 evaluable non-synovial sarcoma tumors (5 thymomas, 5 sarcomatoid mesotheliomas, 10 schwannomas, 9 mesenchymal chondrosarcomas, 20 solitary fibrous tumors, 19 Ewing sarcomas, and 25 malignant peripheral nerve sheath tumors). A few schwannomas and malignant peripheral nerve sheath tumors showed mosaic or complete loss of SMARCB1 expression. Reduced expression of SMARCB1 immunoreactivity was therefore found to be highly sensitive and specific for synovial sarcoma, and can be useful for rapidly and accurately confirming the diagnosis of synovial sarcoma. This reduction in SMARCB1 expression likely reflects the BAF47 ejection mechanism of the SS18-SSX fusion product and can therefore be viewed as an indirect visualization of this fusion product.

Identification of a blood-borne miRNA signature of synovial sarcoma

Background

Synovial sarcoma account for approximately 10 % of all soft-tissue tumors and occur most frequently in young adults. A specific translocation in this sarcoma induces fusion of the SYT gene on chromosome 18 to the SSX genes on chromosome X, leading to proliferation of the tumor cells. The need for non-invasive biomarkers indicating recurrence and activity of this disease has sparked research into short non-coding RNA known as microRNA (miRNA).

Methods

Blood samples of patients with active synovial sarcoma and of synovial sarcoma patients in complete remission as well as of healthy donors and patients with active leiomyosarcoma, MPNST, Ewing sarcoma and liposarcoma were collected. Whole blood RNA was extracted and samples of patients with active synovial sarcoma and of healthy donors were analyzed using an Affymetrix GeneChip miRNA Array v. 4.0. qRT-PCR was carried out to confirm a panel of miRNAs which where differentially expressed in the miRNA array. This miRNA-panel was further evaluated in patients with synovial sarcoma in complete remission and patients with active leiomyosarcoma, MPNST, Ewing sarcoma and liposarcoma as well as in an independent cohort of synovial sarcoma patients.

Results

Unsupervised hierarchical clustering of the miRNA arrays separated patients with active synovial sarcoma from healthy controls. A panel of seven miRNAs (miR-99a-5p, miR-146b-5p, miR-148b-3p, miR-195-5p, miR-223-3p, miR-500b-3p and miR-505-3p) was further validated by qRT-PCR to be significantly upregulated in synovial sarcoma patients. Moreover, most of the analyzed miRNAs were shown to be significantly upregulated in synovial sarcoma patients compared to leiomyosarcoma, MPNST, Ewing sarcoma and liposarcoma patients. Validation of the miRNA panel in an independent cohort of synovial sarcoma patients confirmed higher expression levels compared to healthy controls and patients in complete remission.

Conclusion

Our results have identified a specific whole blood miRNA signature that may serve as an independent biomarker for the diagnosis of local recurrence or distant metastasis of synovial sarcoma. It even distinguishes synovial sarcoma from other sarcoma subtypes, thus potentially serving as a specific biomarker for synovial sarcoma.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-015-0424-z) contains supplementary material, which is available to authorized users.

Primary intraocular synovial sarcoma in the post retinal detachment operative state

Synovial sarcoma generally arises in the deep soft tissue, although it has been described at virtually every anatomic site except in the eyeball. We report the case of a 48-year-old woman who had a history of retinal detachment surgery and who had undergone vitrectomy and the insertion of a solid silicon explant 24 years previously. She reported a visual field defect. Funduscopy and MRI revealed a tumour just behind the iris in the left eyeball, and enucleation was performed. Microscopic examination of the tumour revealed uniform spindle cells in a fascicular arrangement with frequent mitotic figures. Immunohistochemistry showed that the tumour was positive for TLE1 and epithelial membrane antigen and fluorescent in situ hybridisation revealed that the tumour had a rearrangement of the SYT gene. Reverse transcription (RT)-PCR confirmed the presence of a SYT-SSX2 fusion transcript. On the basis of these histomorphological and molecular features, the diagnosis of poorly differentiated synovial sarcoma was rendered.

Detection of Rare Variant of SS18-SSX1 Fusion Gene and Mutations of Important Cancer-Related Genes in Synovial Sarcoma of the Lip: Gene Analyses of a Case and Literature Review

Synovial sarcoma (SS) accounts for 5 to 10% of soft tissue sarcomas; however, intraoral SS is rare. Histopathologically, SS shows a biphasic pattern with epithelial and spindle cell components or a monophasic pattern with only spindle cells. The precise diagnosis of SS, especially at an unusual site, is often a challenge to pathologists and clinical oncologists, because the differential diagnosis of SS includes a broad range of tumors, such as soft tissue sarcomas and carcinomas. In the present case, the patient was a 50-year-old woman who presented with the chief complaint of swelling and a slowly enlarging mass of the lower lip in the mucolabial fold region. The mass was covered with intact mucosa and intraoral examination showed no malignant findings. The clinical diagnosis was a benign tumor and a probable salivary gland tumor. Macroscopically, the excised mass also indicated a benign tumor; however, histopathologic findings suggested the diagnosis of SS. For definitive diagnosis, genetic analyses were performed with conventional polymerase chain reaction and next-generation sequencing. As a result, a rare variant of the SS18-SSX1 fusion transcript, which could not be identified by routine procedures for genetic diagnosis, was detected. In addition, 8 missense mutations of cancer-related genes were confirmed. Detection of the fusion transcript is widely used in the diagnosis of SS; however, reported cases of transcript variants of each fusion gene type are limited. Reports of mutational analysis of cancer-related genes on SS also are rare. The accumulation of rare transcript variants and the cytogenetic characters of SS are suggested to be necessary for assuming a genetic diagnosis of SS.

Abdominal monophasic synovial sarcoma is a morphological and immunohistochemical mimic of gastrointestinal stromal tumour

AIMS

Synovial sarcomas may arise within retroperitoneal or pelvic tissues or, more rarely, within the luminal gastrointestinal tract. This case series aims to demonstrate how such primary abdominal synovial sarcomas may particularly mimic gastrointestinal stromal tumour (GIST) on both morphological and immunohistochemical grounds.

METHODS AND RESULTS

Four cases of primary abdominal synovial sarcoma were reviewed morphologically and with immunohistochemistry, fluorescence in-situ hybridization with an SS18 break-apart probe, and KIT/PDGFRA mutation analysis. The four patients comprised two males and two females, with a median age of 42 years (range: 17-59 years). Two synovial sarcomas arose within the stomach, one within the small-intestine mesentery, and the fourth within the retroperitoneum. All four tumours showed only a monophasic spindle cell component in the tissues available for review. All four tumours showed DOG1 immunopositivity, and three coexpressed CD117. Three tested cases did not show activating KIT or PDGFRA mutations, whereas all four cases showed chromosomal rearrangement of SS18.

CONCLUSIONS

A diagnosis of synovial sarcoma should be considered particularly if an abdominal spindle cell neoplasm shows a haemangiopericytomatous pattern and diffuse CD99 and CD56 immunopositivity. A confident distinction between abdominal synovial sarcoma and GIST requires KIT/PDGFRA mutation analyses and specific molecular testing for synovial sarcoma.

Isocitrate dehydrogenase 1 mutations (IDH1) and p16/CDKN2A copy number change in conventional chondrosarcomas

To determine whether IDH1 mutations are present in primary and relapsed (local and distal) conventional central chondrosarcomas; and secondly, to assess if loss of p16/CDKN2A is associated with tumour grade progression, 102 tumour samples from 37 patients, including material from presenting and relapse events, were assessed. All wild-type cases for IDH1 R132 substitutions were also tested for IDH2 R172 and R140 alterations. The primary tumour and the most recent relapse sample were tested for p16/CDKN2A by interphase fluorescence in situ hybridisation. An additional 120 central cartilaginous tumours from different patients were also tested for p16/CDKN2A copy number. The study shows that if an IDH1 mutation were detected in a primary central chondrosarcoma, it is always detected at the time of presentation, and the same mutation is detected in local recurrences and metastatic events. We show that p16/CDKN2A copy number variation occurs subsequent to the IDH1 mutation, and confirm that p16/CDKN2A copy number variation occurs in 75 % of high grade central chondrosarcomas, and not in low grade cartilaginous tumours. Finally, p16/CDKN2A copy number variation is seen in both the IDH1 wild-type and mutant cartilaginous central tumours.

Synovial sarcoma: defining features and diagnostic evolution

Synovial sarcoma (SS) is a malignant mesenchymal neoplasm with variable epithelial differentiation, with a propensity to occur in young adults and which can arise at almost any site. It is generally viewed and treated as a high-grade sarcoma. As one of the first sarcomas to be defined by the presence of a specific chromosomal translocation leading to the production of the SS18-SSX fusion oncogene, it is perhaps the archetypal "translocation-associated sarcoma," and its translocation remains unique to this tumor type. Synovial sarcoma has a variety of morphologic patterns, but its chief forms are the classic biphasic pattern, of glandular or solid epithelial structures with monomorphic spindle cells and the monophasic pattern, of fascicles of spindle cells with only immunohistochemical or ultrastructural evidence of epithelial differentiation. However, there is significant morphologic heterogeneity and overlap with a variety of other neoplasms, which can cause diagnostic challenge, particularly as the immunoprofile is varied, SS18-SSX is not detected in 100% of SSs, and they may occur at unusual sites. Correct diagnosis is clinically important, due to the relative chemosensitivity of SS in relation to other sarcomas, for prognostication and because of the potential for treatment with specific targeted therapies in the near future. We review SS, with emphasis on the diagnostic spectrum, recent immunohistochemical and genetic findings, and the differential diagnosis.

Tumors that mimic asbestos-related mesothelioma: time to consider a genetics-based tumor registry?

The diagnosis of mesothelioma is not always straightforward, despite known immunohistochemical markers and other diagnostic techniques. One reason for the difficulty is that extrapleural tumors resembling mesothelioma may have several possible etiologies, especially in cases with no meaningful history of amphibole asbestos exposure. When the diagnosis of mesothelioma is based on histologic features alone, primary mesotheliomas may resemble various primary or metastatic cancers that have directly invaded the serosal membranes. Some of these metastatic malignancies, particularly carcinomas and sarcomas of the pleura, pericardium and peritoneum, may undergo desmoplastic reaction in the pleura, thereby mimicking mesothelioma, rather than the primary tumor. Encasement of the lung by direct spread or metastasis, termed pseudomesotheliomatous spread, occurs with several other primary cancer types, including certain late-stage tumors from genetic cancer syndromes exhibiting chromosomal instability. Although immunohistochemical staining patterns differentiate most carcinomas, lymphomas, and mestastatic sarcomas from mesotheliomas, specific genetic markers in tumor or somatic tissues have been recently identified that may also distinguish these tumor types from asbestos-related mesothelioma. A registry for genetic screening of mesothelioma cases would help lead to improvements in diagnostic criteria, prognostic accuracy and treatment efficacy, as well as improved estimates of primary mesothelioma incidence and of background rates of cancers unrelated to asbestos that might be otherwise mistaken for mesothelioma. This information would also help better define the dose-response relationships for mesothelioma and asbestos exposure, as well as other risk factors for mesothelioma and other mesenchymal or advanced metastatic tumors that may be indistinguishable by histology and staining characteristics.

Fibroblastic growth factor receptor 1 amplification in osteosarcoma is associated with poor response to neo-adjuvant chemotherapy

Osteosarcoma, the most common primary bone sarcoma, is a genetically complex disease with no widely accepted biomarker to allow stratification of patients for treatment. After a recent report of one osteosarcoma cell line and one tumor exhibiting fibroblastic growth factor receptor 1 (FGFR1) gene amplification, the aim of this work was to assess the frequency of FGFR1 amplification in a larger cohort of osteosarcoma and to determine if this biomarker could be used for stratification of patients for treatment. About 352 osteosarcoma samples from 288 patients were analyzed for FGFR1 amplification by interphase fluorescence in situ hybridization. FGFR1 amplification was detected in 18.5% of patients whose tumors revealed a poor response to chemotherapy, and no patients whose tumors responded well to therapy harbored this genetic alteration. FGFR1 amplification is present disproportionately in the rarer histological variants of osteosarcoma. This study provides a rationale for inclusion of patients with osteosarcoma in clinical trials using FGFR kinase inhibitors.

Models of biobanking and tissue preservation: RNA quality in archival samples in pathology laboratories and "in vivo biobanking" by tumor xenografts in nude mice-two models of quality assurance in pathology

Tissue banks represent essential resources and platforms for biomedical research serving basic, translational, and clinical research projects. In this article, we describe 2 models of biobanking and tissue preservation with different approaches and aims. Archive tissue biobanking is described here as a resource of residual pathology tissues for translational research, which represents the huge clinical heterogeneity. In this context, managing of tissues and RNA quality in archive tissue are discussed. The other model of tissue biobanking is referred to as xenograft tissue banking, which represents an alternative method for obtaining large amounts of tissue, over an indefinite period, in so far as the tumor can be transferred in vivo over generations, maintaining the histological and genetic particularities. A description of the method and examples of the application are given with particular emphasis on sarcomas (Ewing's sarcoma/primitive neuroectodermal sarcoma, synovial sarcomas, and rhabdomyosarcomas) and early stages of tumor angiogenesis in sarcomas.

Loss of SS18-SSX1 inhibits viability and induces apoptosis in synovial sarcoma

BACKGROUND

Most synovial sarcomas contain a chromosomal translocation t(X;18), which results in the formation of an oncoprotein SS18-SSX critical to the viability of synovial sarcoma.

QUESTIONS/PURPOSES

We (1) established and characterized three novel synovial sarcoma cell lines and asked (2) whether inhibition of SS18-SSX1 decreases cell viability in these cell lines; and (3) whether reduction in viability after SS18-SSX1 knockdown is caused by apoptosis. After identifying a specific posttranscriptional splice variant in our cell lines, we asked (4) whether this provides a survival benefit in synovial sarcoma.

METHODS

Cells lines were characterized. SS18-SSX1 knockdown was achieved using a shRNA system. Cell viability was assessed by WST-1 analysis and apoptosis examined by caspase-3 activity.

RESULTS

We confirmed the SS18-SSX1 translocation in all cell lines and identified a consistent splicing variant. We achieved successful knockdown of SS18-SSX1 and with this saw a significant reduction in cell viability. Decreased viability was a result of increased apoptosis. Reintroduction of the exon 8 sequence into cells reduced cell viability in all cell lines.

CONCLUSIONS

We confirmed the presence of the SS18-SSX1 translocation in our cell lines and its importance in the survival of synovial sarcoma. We have also demonstrated that reduction in cell viability is related to an increase in apoptosis. In addition, we have identified a potential mediator of SS18-SSX function in exon 8.

CLINICAL RELEVANCE

SS18-SSX represents a tumor-specific target in synovial sarcoma. Exploitation of SS18-SSX and its protein partners will allow us to develop potent tumor-specific therapeutic agents.

Primary monophasic synovial sarcoma of the kidney: a case report and review of literature

Primary synovial sarcoma (SS) of the kidney is a rare neoplasm and its presenting features are similar to other common renal tumors, making early diagnosis difficult. To date, few cases have been reported in the literature. Primary renal SSs can exist in either a monophasic or a biphasic pattern, the former being more common and tending to have a better prognosis than the biphasic variant. Herein we describe a case of primary renal SS that was diagnosed based on histopathology and immunohistochemistry after radical nephrectomy. Fusion gene product analysis was also done by FISH and RT-PCR. Patient follow-up and literature review are presented, focused on systemic therapy. We highlight that these tumors should be correctly diagnosed as clinical results and specific treatment are distinct from primary epithelial renal cell carcinoma. Adjuvant chemotherapy should be tailored for each patient in the management of disease, although its role still remains unclear.

Challenges and controversies in the diagnosis of malignant mesothelioma: Part 2. Malignant mesothelioma subtypes, pleural synovial sarcoma, molecular and prognostic aspects of mesothelioma, BAP1, aquaporin-1 and microRNA

Pleural malignant mesothelioma (MM) includes several unusual and even rare but distinctive histological subtypes, in addition to the usual subdivision into epithelioid, biphasic and sarcomatoid MM. Criteria for discrimination between fibrous pleuritis versus desmoplastic mesothelioma include evidence of neoplastic invasion for diagnosis of desmoplastic MM, but this histological assessment is complicated by the recently-described 'fake fat phenomenon' in cases of fibrous pleuritis. The distinction between biphasic and monophasic synovial sarcoma of the pleura versus biphasic and sarcomatoid MM can be problematical and is most cogently based upon molecular detection of the t(X;18) translocation, whereas a clear diagnosis of MM for a pleural tumour histologically resembling synovial sarcoma is favoured by a negative result for this translocation and, probably, microRNA evidence supportive of a diagnosis of MM. Aquaporin-1 (AQP1) is a molecule involved in the growth of MM cells, and yet is a factor reported to correlate with improved survival rates for MM with an epithelioid component, in comparison to AQP1-poor MM, as assessed from AQP1 expression by epithelioid MM cells only (apart from co-expression by stromal endothelial cells in addition to the tumour cells). Recent reports have also focused upon germline mutations in the BRCA1-associated protein 1 (BAP1), not only in cases of familial mesothelioma, but also BAP1 deletion in sporadic MM. Prognostic factors for MM include not only the histological subtypes, but other independent variables that include (among others), AQP1 expression by mesothelioma cells, the clinical status of the patient, the serum neutrophil:lymphocyte ratio and blood thrombocytosis.

ALDH1 is an immunohistochemical diagnostic marker for solitary fibrous tumours and haemangiopericytomas of the meninges emerging from gene profiling study

Background

Solitary Fibrous Tumours (SFT) and haemangiopericytomas (HPC) are rare meningeal tumours that have to be distinguished from meningiomas and more rarely from synovial sarcomas. We recently found that ALDH1A1 was overexpressed in SFT and HPC as compared to soft tissue sarcomas. Using whole-genome DNA microarrays, we defined the gene expression profiles of 16 SFT/HPC (9 HPC and 7 SFT). Expression profiles were compared to publicly available expression profiles of additional SFT or HPC, meningiomas and synovial sarcomas. We also performed an immunohistochemical (IHC) study with anti-ALDH1 and anti-CD34 antibodies on Tissue Micro-Arrays including 38 SFT (25 meningeal and 13 extrameningeal), 55 meningeal haemangiopericytomas (24 grade II, 31 grade III), 163 meningiomas (86 grade I, 62 grade II, 15 grade III) and 98 genetically confirmed synovial sarcomas.

Results

ALDH1A1 gene was overexpressed in SFT/HPC, as compared to meningiomas and synovial sarcomas. These findings were confirmed at the protein level. 84% of the SFT and 85.4% of the HPC were positive with anti-ALDH1 antibody, while only 7.1% of synovial sarcomas and 1.2% of meningiomas showed consistent expression. Positivity was usually more diffuse in SFT/HPC compared to other tumours with more than 50% of tumour cells immunostained in 32% of SFT and 50.8% of HPC. ALDH1 was a sensitive and specific marker for the diagnosis of SFT (SE = 84%, SP = 98.8%) and HPC (SE = 84.5%, SP = 98.7%) of the meninges. In association with CD34, ALDH1 expression had a specificity and positive predictive value of 100%.

Conclusion

We show that ALDH1, a stem cell marker, is an accurate diagnostic marker for SFT and HPC, which improves the diagnostic value of CD34. ALDH1 could also be a new therapeutic target for these tumours which are not sensitive to conventional chemotherapy.

Primary monophasic synovial sarcoma of the tonsil: immunohistochemical and molecular study of a case and review of the literature

Synovial sarcoma (SS) arises primarily in the lower extremities with a predilection for sites in proximity to large joints, such as the knee. It rarely occurs in the head and neck region, and the tonsil is an unusual site for the tumor, with only eight previously published cases in this anatomical site. We present a case of a primary monophasic SS arising in the right tonsil in a 63-year-old male. His medical history was noncontributory. Immunohistochemistry showed that cytokeratin OSCAR, EMA, Bcl-2, vimentin, PGP 9.5, and TLE1 were diffusely positive. A molecular analysis using RT-PCR indicated that the patient was positive for the SYT/SSX1 fusion transcript. A diagnosis of monophasic synovial sarcoma of the tonsil was made.

The CD133+ subpopulation of the SW982 human synovial sarcoma cell line exhibits cancer stem-like characteristics

Several soft tissues sarcomas have been reported to contain cancer stem-like cells (CSCs) or tumor-initiating cells, based on their ability to initiate and sustain tumor growth. However, these cells have not yet been identified in the human synovial sarcoma cell line SW982. CD133, a surface glycoprotein specific to stem and progenitor cells, has been described as a CSC marker in different tumor types. In the present study, we identified a CSC subpopulation in SW982 cells using the CD133 cell surface marker. CD133-positive (CD133(+)) cells were identified in SW982 cells (8.59%); these cells showed an increased ability to form spherical colonies and could self-renew in serum-starved culture conditions, compared to CD133-negative (CD133(-)) cells. Real-time PCR analysis of stemness genes revealed that the CD133+ subpopulation expresses higher levels of Bmi1, c-Myc, Nanog, Oct3/4 and Sox2. CD133(+) cells showed increased resistance to cisplatin (CDDP) and doxorubicin (DXR), possibly due to upregulation of the ABCG2 drug transporter gene. In vivo studies revealed that the CD133(+) subpopulation is highly tumorigenic. These findings indicate that CD133(+) SW982 cells have characteristics similar to CSCs. This discovery may lead to the development of novel therapies that specifically target CD133(+) synovial sarcoma CSCs.

Synovial sarcoma arising in the vulva cytogenetically confirmed by SYT break-apart rearrangement fluorescence in situ hybridization: A case report and discussion of diagnostic methods

Synovial sarcoma (SS) is a soft tissue sarcoma of unknown histogenesis that rarely occurs in the female genital tract. We report a case of SS occurring in the right vulva of a young Japanese female. The tumor was composed of poorly differentiated rounded cell areas, surrounded by fibroblastic spindle-shaped cell areas. Immunohistochemically, the tumor cells were focally positive for cytokeratin, vimentin, CD99, Bcl-2 and neuron-specific enolase. The tumor was suspected, but was difficult to confirm as it was an SS based solely on light-microscopic and immunohistochemical findings. Although reverse transcription polymerase chain reaction (RT-PCR) failed to detect SS-specific SYT-SSX fusion gene transcripts using an RNA sample extracted from the formalin-fixed paraffin-embedded tumor tissue, SYT break-apart rearrangement fluorescence in situ hybridization (SYT bar-FISH) successfully confirmed our diagnosis of SS for the tumor. Thus, SYT bar-FISH may be more suitable for the purpose of the molecular diagnosis of SS than conventional RT-PCR when using archival formalin-fixed paraffin-embedded tissue specimens.

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.

Pericardial synovial sarcoma, a potential for misdiagnosis: clinicopathologic and molecular cytogenetic analysis of three cases with literature review

Synovial sarcomas arising in unexpected locations may lead to diagnostic challenges. In this report, we describe 3 cases of synovial sarcoma that manifested clinically as primary pericardial lesions. All 3 cases occurred in men in their fourth decade. Fever, cough, chest pain, and chest distress were the most common symptoms. Histologically, 2 of the tumors were spindle cell monophasic, and 1 tumor was biphasic. By immunohistochemical studies, the tumor cells were positive for cytokeratins and epithelial membrane antigen. In addition, the tumor cells displayed focal immunoreactivity for calretinin, cytokeratin 5/6, and HBME-1, resulting in the initial interpretations of malignant mesotheliomas. None of the 3 cases were diagnosed correctly until subsequent molecular cytogenetic assays demonstrated the presence of SYT gene rearrangements. As there are overlapping morphologic features between pericardial synovial sarcoma and mesothelioma, molecular analysis is essential for differential diagnoses.

Unknown partner for USP6 and unusual SS18 rearrangement detected by fluorescence in situ hybridization in a solid aneurysmal bone cyst

USP6 rearrangement is the most common genetic abnormality in primary aneurysmal bone cyst, and SS18 rearrangement has not been previously described in any type of tumor where synovial sarcoma was excluded from the differential diagnosis. We report a case of solid aneurysmal bone cyst in which fluorescence in situ hybridization (FISH) analysis indicated rearrangements of both USP6 and SS18, but histologic features were consistent with aneurysmal bone cyst throughout the lesion. Reverse-transcription polymerase chain reaction (RT-PCR) for the SS18-SSX1 and SS18-SSX2 translocations, identity testing, and SS18 FISH were performed on cytogenetic monolayer cultures and formalin-fixed paraffin-embedded (FFPE) tissue. Genomic microarray, FISH, and immunohistochemistry were performed on follow-up studies of the FFPE specimen. The karyotype was 45,X,add(X)(p11.2),add(4)(q13),add(8)(p21),-13,add(17)(p11.2),add(18)(q11.2) in all 20 cells analyzed from monolayer cultures. The karyotype showed no cytogenetically visible alterations of chromosomal regions harboring known partners for USP6. Metaphase FISH with a commercial SS18 break-apart probe showed translocation of the 5' portion of the SS18 probe to the short arm of the derivative X, as is observed in synovial sarcoma. RT-PCR showed no evidence of a SS18-SSX fusion, and immunohistochemistry was negative for TLE1, EMA, and cytokeratin AE1/3 expression. FISH on FFPE sections with a custom break-apart probe flanking USP6 showed evidence for a USP6 rearrangement throughout the tumor (25-50%). FISH on FFPE sections with a commercial SS18 break-apart FISH probe showed more variable results (0-50% split signals). There was no evidence of a SS18-USP6 fusion by FISH or RT-PCR. A molecular inversion probe array revealed a deletion encompassing the entire SS18 gene and its promoter, as well as portions of the region targeted by the commercial SS18 FISH probe. In conclusion, results obtained from commercially available FISH probes may occasionally yield misleading results. In this case, the SS18 rearrangement by FISH resulted from a complex rearrangement of 18q11.2 with a deletion of the SS18 gene. The translocation partner for USP6 remains unknown in this case.

Immunohistochemical staining for TLE1 distinguishes synovial sarcoma from histologic mimics

Transducer-like enhancer of split 1 (TLE1) is overexpressed in synovial sarcomas. We investigated TLE1 expression by immunohistochemical analysis in a well-characterized series of synovial sarcomas and other mesenchymal tumors most commonly considered in the differential diagnosis. Whole tissue sections of 212 tumors were evaluated: 73 synovial sarcomas (23 biphasic, 28 monophasic, 22 poorly differentiated), 47 malignant peripheral nerve sheath tumors (MPNSTs), 49 solitary fibrous tumors (SFTs), 20 fibrosarcomatous variants of dermatofibrosarcoma protuberans, and 23 Ewing sarcomas/primitive neuroectodermal tumors (PNETs). All monophasic and poorly differentiated SSs and Ewing sarcoma/PNETs were previously confirmed to harbor t(X;18) and EWSR1 gene rearrangements, respectively. In total, 60 (82%) of 73 synovial sarcomas were positive for TLE1, including 18 biphasic (78%), 22 monophasic (79%), and 20 poorly differentiated (91%) tumors. Of the other tumors, only 7 MPNSTs (15%) and 4 SFTs (8%) were positive for TLE1, most of which showed only weak staining. TLE1 is a sensitive and specific marker for synovial sarcoma and can be helpful to distinguish synovial sarcoma from histologic mimics, particularly if moderate or strong staining is observed. In this study, only a small subset of MPNSTs and SFTs showed limited staining for TLE1.

Expression profiling in soft tissue sarcomas with emphasis on synovial sarcoma, gastrointestinal stromal tumor, and leiomyosarcoma

Sarcomas are defined as malignant neoplasms derived from mesenchymal tissues. A variety of different molecular approaches, including gene expression profiling, have identified candidate biomarkers and insights into sarcoma biology that will aid in the diagnosis and treatment of these tumors. Many gene expression profiling findings have been translated into immunohistochemical tests for diagnostic, prognostic, or predictive purposes. This review details gene expression studies done in 3 sarcomas, synovial sarcoma, gastrointestinal stromal tumor, and leiomyosarcoma.

Detection of SYT and EWS gene rearrangements by dual-color break-apart CISH in liquid-based cytology samples of synovial sarcoma and Ewing sarcoma/primitive neuroectodermal tumor

To improve cytologic diagnostic accuracy for translocation-associated sarcomas, we explored dual-color break-apart (dc) chromogenic in situ hybridization (CISH) on liquid-based cytology (LBC) samples of 2 prototypic sarcomas: synovial sarcoma (SS) and Ewing sarcoma/primitive neuroectodermal tumor (ES/PNET). LBC samples of 10 cases of SS and 9 cases of ES/PNET were subjected to dc-CISH using probes for the specifically rearranged genes in each tumor entity: SYT in SS and EWS in ES/PNET. Rearranged SYT was successfully detected in all SSs but not in any ES/PNETs. In contrast, EWS rearrangement was identified in all ES/PNETs but not in any SSs. These results were validated by dc-fluorescence in situ hybridization and reverse transcription-polymerase chain reaction. dc-CISH on LBC samples is a reliable modality to detect gene rearrangements in sarcomas. This system has a clear advantage over other methods, enabling simultaneous visualization of the genetic abnormality and well-preserved, nonoverlapping cytomorphologic features with clear background under bright-field microscope.

The benefits of molecular pathology in the diagnosis of musculoskeletal disease : part I of a two-part review: soft tissue tumors

Bone and soft tissue metabolic and neoplastic diseases are increasingly characterized by their molecular signatures. This has resulted from increased knowledge of the human genome, which has contributed to the unraveling of molecular pathways in health and disease. Exploitation of this information has allowed it to be used for practical diagnostic purposes. The aim of the first part of this two-part review is to provide an up-to-date review of molecular genetic investigations that are available and routinely used by specialist musculoskeletal histopathologists in the diagnosis of neoplastic disease. Herein we focus on the benefits of employing well characterized somatic mutations in soft tissue lesions that are commonly employed in diagnostic pathology today. The second part highlights the known somatic and germline mutations implicated in osteoclast-rich lesions of bone, and the genetic changes that disturb phosphate metabolism and result in a variety of musculoskeletal phenotypes. Finally, a brief practical guide of how to use and provide a molecular pathology service is given.