t(X;18)(p11.2;q11.2) SS18-SSX1 in Synovial Sarcoma A SYT-SSX fusion gene resulting from the chromosomal translocation t(X;18)(p11;q11) is characteristic nearly all synovial sarcomas. This translocation fuses the SS18 (SYT) gene from chromosome 18 to one of three homologous genes at Xp11: SSX1, SSX2 or SSX4.
t(X;18)(p11.2;q11.2) SS18-SSX2 in Synovial Sarcoma A SYT-SSX fusion gene resulting from the chromosomal translocation t(X;18)(p11;q11) is characteristic nearly all synovial sarcomas. This translocation fuses the SS18 (SYT) gene from chromosome 18 to one of three homologous genes at Xp11: SSX1, SSX2 or SSX4.
t(X;18)(p11.2;q11.2) SS18-SSX4 in Synovial Sarcoma A SYT-SSX fusion gene resulting from the chromosomal translocation t(X;18)(p11;q11) is characteristic nearly all synovial sarcomas. This translocation fuses the SS18 (SYT) gene from chromosome 18 to one of three homologous genes at Xp11: SSX1, SSX2 or SSX4.
Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).
Atlas of Genetics and Cytogenetics in Oncology and Haematology
SS18 OMIM, Johns Hopkin University Referenced article focusing on the relationship between phenotype and genotype.
SS18 International Cancer Genome Consortium. Summary of gene and mutations by cancer type from ICGC
SS18 Cancer Genome Anatomy Project, NCI Gene Summary
SS18 COSMIC, Sanger Institute Somatic mutation information and related details
SS18 TICdb, Universidad de Navarra Search the database of Translocation breakpoints In Cancer for "SS18"
SS18 GEO Profiles, NCBI Search the gene expression profiles from curated DataSets in the Gene Expression Omnibus (GEO) repository.
Latest Publications: SS18 (cancer-related)
Olofson AM, Linos K Primary Intraprostatic Synovial Sarcoma. Arch Pathol Lab Med. 2017; 141(2):301-304 [PubMed] Related Publications
Primary intraprostatic synovial sarcoma is a rare presentation of an otherwise well-studied disease, and it is one of the few primary sarcomas to occur in the prostate. Ancillary diagnostic techniques including immunohistochemistry and molecular genetics are useful to establish a definitive diagnosis. Despite its unorthodox location, it shares histologic and molecular genetic characteristics with tumors found elsewhere in the body. Most notably, the chromosomal translocation t(X;18)(p11;q11) encodes a chimeric transcription-activating protein, SS18-SSX, which has been identified as the primary driver mutation. The SS18-SSX fusion gene provides a consistent and dependable means of establishing a definitive diagnosis via reverse transcription-polymerase chain reaction or fluorescence in situ hybridization. Recent studies have continued to provide insight into the oncogenesis of this disease. The goal of this review is to elaborate on the clinicopathologic characteristics and underline those techniques that best facilitate the diagnosis of primary intraprostatic synovial sarcoma.
Machado I, Navarro L, Pellin A, et al. Defining Ewing and Ewing-like small round cell tumors (SRCT): The need for molecular techniques in their categorization and differential diagnosis. A study of 200 cases. Ann Diagn Pathol. 2016; 22:25-32 [PubMed] Related Publications
BACKGROUND: Differentiation of Ewing sarcoma family of tumors (ESFT) and Ewing-like tumors remains problematic. Certain ESFT with morphological and immunohistochemical (IHC) profiles lack the EWSR1-ETS transcript. To improve diagnostic accuracy we investigated the presence of several specific transcripts in 200 small round cell tumors (SRCT) displaying ESFT morphology and immunophenotype in which EWSR1 FISH analysis was non-informative or negative. DESIGN: 200 tumors (formalin-fixed, paraffin-embedded) were analyzed by RT-PCR. All tumors were tested for EWSR1-ETS, EWSR1/WT1, PAX3/7-FOX01 or SYT/SSX transcripts, and the negative tumors were subsequently analyzed for CIC/DUX4, BCOR/CCNB3 and CIC/FOX04 transcripts. RESULTS: 133 (66.5%) ESFT displayed one of the above EWSR1-ETS translocations. Three cases (1.5%) revealed the SYT-SSX transcript for Synovial sarcoma, and one (0.5%) a EWSR1-WT1 transcript for Desmoplastic Small Round Cell tumor. The CIC-DUX4 translocation was found in six Ewing-like tumors (3%) with CD99 positivity. The BCOR-CCNB3 gene fusion was observed in 5 tumors (2.5%) displaying round or spindle cells with strong CCNB3 IHC expression in 3 tumors. Moreover, RT-PCR failed to detect any gene fusion transcripts in 19 tumors (9.5%) and were considered "undifferentiated small round cell sarcoma" (SRCS). Molecular biology results were non-informative in 33 SRCTs (16.5%) due to RNA degradation through inadequate fixation and/or decalcification. CONCLUSION: Our analysis of 200 SRCTs confirms the molecular heterogeneity of neoplasms with ESFT morphology and highlight that molecular studies with RT-PCR including new emerging gene fusion transcripts are mandatory for the diagnosis when EWSR1 FISH is negative or non-informative. The incidence of CIC-DUX4, BCOR-CCNB3 and CIC-FOX04 transcripts was relatively low. A small group of Ewing-like sarcomas or undifferentiated SRCS remains unclassified. Adopting appropriate tissue fixation and processing protocols is important to avoid degradation of fixed/embedded tissue when no frozen tumor is available.
Sugita S, Asanuma H, Hasegawa T Diagnostic use of fluorescence in situ hybridization in expert review in a phase 2 study of trabectedin monotherapy in patients with advanced, translocation-related sarcoma. Diagn Pathol. 2016; 11:37 [PubMed] Free Access to Full ArticleRelated Publications
BACKGROUND: Fluorescence in situ hybridization (FISH) is one of the most powerful genetic analysis tools for pathological diagnoses. FISH can detect various genetic abnormalities including gene translocation that was specifically found in translocation-related sarcomas (TRSs). Here, we report the use of FISH in expert review in a phase 2 study of trabectedin monotherapy for patients with advanced TRS. METHODS: TRS patients (n = 76) were enrolled in the trial at 12 study sites after pathological diagnoses were made, including morphological examination with or without evidence of translocation by genetic testing. Following histological reviews of the representative specimens at the study sites, we performed immunohistochemistry using the appropriate antibodies and FISH for genetic confirmation of the tumor types in the expert review. RESULTS: Among the 76 TRS cases, no split signal for SS18 probe was detected by FISH in three synovial sarcoma cases that were diagnosed at the study sites. Malignant peripheral nerve sheath tumor (MPNST) was diagnosed in two cases and sarcomatoid carcinoma in one. One of the cases was a small round cell variant of MPNST. After excluding these three cases, we assessed the other 73. There were no split signals detected in 7 of the 73 cases by FISH analysis, due to decalcification and hyperfixation procedures. Excluding these seven cases, FISH detected translocations in 95 % (63/66) of the study cases with a high sensitivity. CONCLUSIONS: The diagnosis of TRS by FISH was highly sensitive and enabled genetic confirmation of the pathological diagnoses. We strongly recommend FISH as a confirmatory diagnostic test for TRS, which would enable the selection of patients with TRS in whom trabectedin is expected to be effective. This study was done in part that registered with Japan Pharmaceutical Information Center, number JapicCTI-121850.
Expression of the SS18/SYT-SSX fusion protein is believed to underlie the pathogenesis of synovial sarcoma (SS). Recent evidence suggests that deregulation of the Wnt pathway may play an important role in SS but the mechanisms whereby SS18-SSX might affect Wnt signaling remain to be elucidated. Here, we show that SS18/SSX tightly regulates the elevated expression of the key Wnt target AXIN2 in primary SS. SS18-SSX is shown to interact with TCF/LEF, TLE and HDAC but not β-catenin in vivo and to induce Wnt target gene expression by forming a complex containing promoter-bound TCF/LEF and HDAC but lacking β-catenin. Our observations provide a tumor-specific mechanistic basis for Wnt target gene induction in SS that can occur in the absence of Wnt ligand stimulation.
Ogino H, Hanibuchi M, Takizawa H, et al. Primary Pulmonary Synovial Sarcoma Showing a Prolonged Survival with Multimodality Therapy. Intern Med. 2016; 55(4):381-7 [PubMed] Related Publications
A 54-year-old man was referred to our hospital due to a mass shadow noted on a chest X-ray. Thoracoscopic lobectomy yielded a diagnosis of primary pulmonary synovial sarcoma according to the histology and SYT-SSX1 gene analyses. Five months after the thoracic surgery, he developed brain metastasis; therefore, we performed resection of the brain metastatic focus followed by radiotherapy. As a local recurrence in the thoracic cavity concurrently emerged, systemic chemotherapy was also administered. These observations indicated that a multidisciplinary approach may be useful against primary pulmonary synovial sarcoma, although there is presently no established therapeutic strategy due to its rarity and highly aggressive nature.
Specht K, Zhang L, Sung YS, et al. Novel BCOR-MAML3 and ZC3H7B-BCOR Gene Fusions in Undifferentiated Small Blue Round Cell Sarcomas. Am J Surg Pathol. 2016; 40(4):433-42 [PubMed] Article available free on PMC after 01/04/2017 Related Publications
Small blue round cell tumors (SBRCTs) are a heterogenous group of tumors that are difficult to diagnose because of overlapping morphologic, immunohistochemical, and clinical features. About two-thirds of EWSR1-negative SBRCTs are associated with CIC-DUX4-related fusions, whereas another small subset shows BCOR-CCNB3 X-chromosomal paracentric inversion. Applying paired-end RNA sequencing to an SBRCT index case of a 44-year-old man, we identified a novel BCOR-MAML3 chimeric fusion, which was validated by reverse transcription polymerase chain reaction and fluorescence in situ hybridization techniques. We then screened a total of 75 SBRCTs lacking EWSR1, FUS, SYT, CIC, and BCOR-CCNB3 abnormalities for BCOR break-apart probes by fluorescence in situ hybridization to detect potential recurrent BCOR gene rearrangements outside the typical X-chromosomal inversion. Indeed, 8/75 (11%) SBRCTs showed distinct BCOR gene rearrangements, with 2 cases each showing either a BCOR-MAML3 or the alternative ZC3H7B-BCOR fusion, whereas no fusion partner was detected in the remaining 4 cases. Gene expression of the BCOR-MAML3-positive index case showed a distinct transcriptional profile with upregulation of HOX-gene signature, compared with classic Ewing's sarcoma or CIC-DUX4-positive SBRCTs. The clinicopathologic features of the SBRCTs with alternative BCOR rearrangements were also compared with a group of BCOR-CCNB3 inversion-positive cases, combining 11 from our files with a meta-analysis of 42 published cases. The BCOR-CCNB3-positive tumors occurred preferentially in children and in bone, in contrast to alternative BCOR-rearranged SBRCTs, which presented in young adults, with a variable anatomic distribution. Furthermore, BCOR-rearranged tumors often displayed spindle cell areas, either well defined in intersecting fascicles or blending with the round cell component, which appears distinct from most other fusion-positive SBRCTs and shares histologic overlap with poorly differentiated synovial sarcoma.
Kasaian K, Wiseman SM, Walker BA, et al. The genomic and transcriptomic landscape of anaplastic thyroid cancer: implications for therapy. BMC Cancer. 2015; 15:984 [PubMed] Article available free on PMC after 01/04/2017 Related Publications
BACKGROUND: Anaplastic thyroid carcinoma is the most undifferentiated form of thyroid cancer and one of the deadliest of all adult solid malignancies. Here we report the first genomic and transcriptomic profile of anaplastic thyroid cancer including those of several unique cell lines and outline novel potential drivers of malignancy and targets of therapy. METHODS: We describe whole genomic and transcriptomic profiles of 1 primary anaplastic thyroid tumor and 3 authenticated cell lines. Those profiles augmented by the transcriptomes of 4 additional and unique cell lines were compared to 58 pairs of papillary thyroid carcinoma and matched normal tissue transcriptomes from The Cancer Genome Atlas study. RESULTS: The most prevalent mutations were those of TP53 and BRAF; repeated alterations of the epigenetic machinery such as frame-shift deletions of HDAC10 and EP300, loss of SMARCA2 and fusions of MECP2, BCL11A and SS18 were observed. Sequence data displayed aneuploidy and large regions of copy loss and gain in all genomes. Common regions of gain were however evident encompassing chromosomes 5p and 20q. We found novel anaplastic gene fusions including MKRN1-BRAF, FGFR2-OGDH and SS18-SLC5A11, all expressed in-frame fusions involving a known proto-oncogene. Comparison of the anaplastic thyroid cancer expression datasets with the papillary thyroid cancer and normal thyroid tissue transcriptomes suggested several known drug targets such as FGFRs, VEGFRs, KIT and RET to have lower expression levels in anaplastic specimens compared with both papillary thyroid cancers and normal tissues, confirming the observed lack of response to therapies targeting these pathways. Further integrative data analysis identified the mTOR signaling pathway as a potential therapeutic target in this disease. CONCLUSIONS: Anaplastic thyroid carcinoma possessed heterogeneous and unique profiles revealing the significance of detailed molecular profiling of individual tumors and the treatment of each as a unique entity; the cell line sequence data promises to facilitate the more accurate and intentional drug screening studies for anaplastic thyroid cancer.
Tamaki S, Fukuta M, Sekiguchi K, et al. SS18-SSX, the Oncogenic Fusion Protein in Synovial Sarcoma, Is a Cellular Context-Dependent Epigenetic Modifier. PLoS One. 2015; 10(11):e0142991 [PubMed] Article available free on PMC after 01/04/2017 Related Publications
The prevalence and specificity of unique fusion oncogenes are high in a number of soft tissue sarcomas (STSs). The close relationship between fusion genes and clinicopathological features suggests that a correlation may exist between the function of fusion proteins and cellular context of the cell-of-origin of each tumor. However, most STSs are origin-unknown tumors and this issue has not yet been investigated in detail. In the present study, we examined the effects of the cellular context on the function of the synovial sarcoma (SS)-specific fusion protein, SS18-SSX, using human pluripotent stem cells (hPSCs) containing the drug-inducible SS18-SSX gene. We selected the neural crest cell (NCC) lineage for the first trial of this system, induced SS18-SSX at various differentiation stages from PSCs to NCC-derived mesenchymal stromal cells (MSCs), and compared its biological effects on each cell type. We found that the expression of FZD10, identified as an SS-specific gene, was induced by SS18-SSX at the PSC and NCC stages, but not at the MSC stage. This stage-specific induction of FZD10 correlated with stage-specific changes in histone marks associated with the FZD10 locus and also with the loss of the BAF47 protein, a member of the SWI/SNF chromatin-remodeling complex. Furthermore, the global gene expression profile of hPSC-derived NCCs was the closest to that of SS cell lines after the induction of SS18-SSX. These results clearly demonstrated that the cellular context is an important factor in the function of SS18-SSX as an epigenetic modifier.
Ito J, Asano N, Kawai A, Yoshida A The diagnostic utility of reduced immunohistochemical expression of SMARCB1 in synovial sarcomas: a validation study. Hum Pathol. 2016; 47(1):32-7 [PubMed] Related Publications
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.
Barrott JJ, Illum BE, Jin H, et al. β-catenin stabilization enhances SS18-SSX2-driven synovial sarcomagenesis and blocks the mesenchymal to epithelial transition. Oncotarget. 2015; 6(26):22758-66 [PubMed] Article available free on PMC after 01/04/2017 Related Publications
β-catenin is a master regulator in the cellular biology of development and neoplasia. Its dysregulation is implicated as a driver of colorectal carcinogenesis and the epithelial-mesenchymal transition in other cancers. Nuclear β-catenin staining is a poor prognostic sign in synovial sarcoma, the most common soft-tissue sarcoma in adolescents and young adults. We show through genetic experiments in a mouse model that expression of a stabilized form of β-catenin greatly enhances synovial sarcomagenesis. Stabilization of β-catenin enables a stem-cell phenotype in synovial sarcoma cells, specifically blocking epithelial differentiation and driving invasion. β-catenin achieves its reprogramming in part by upregulating transcription of TCF/LEF target genes. Even though synovial sarcoma is primarily a mesenchymal neoplasm, its progression towards a more aggressive and invasive phenotype parallels the epithelial-mesenchymal transition observed in epithelial cancers, where β-catenin's transcriptional contribution includes blocking epithelial differentiation.
Fricke A, Ullrich PV, Heinz J, et al. Identification of a blood-borne miRNA signature of synovial sarcoma. Mol Cancer. 2015; 14:151 [PubMed] Article available free on PMC after 01/04/2017 Related Publications
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.
Ito J, Suzuki S, Yoshida A, Mori T Primary intraocular synovial sarcoma in the post retinal detachment operative state. BMJ Case Rep. 2015; 2015 [PubMed] Related Publications
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.
Ng W, Thway K Intraneural Extension of Synovial Sarcoma: Exceptional, or Simply Underrecognized? Int J Surg Pathol. 2015; 23(8):649-51 [PubMed] Related Publications
Intraneural extension of soft tissue sarcomas is uncommon; it is most frequently seen in malignant peripheral nerve sheath tumor, but its occurrence is exceptional in synovial sarcoma. We describe a case arising extraneurally within the deep soft tissues of the forearm, which recurred and resulted in above-elbow amputation, revealing an unexpected finding of diffuse intraneural extension of tumor within a macroscopically normal major nerve. Despite macroscopic and microscopically clear soft tissue margins, the neoplasm had "traveled" a significant distance intraneurally to involve the neural resection margin. This feature does not appear to have been described before; it highlights the issue of whether intraneural spread of synovial sarcoma might have been previously underrecognized, and we discuss briefly some practical implications.
Huo Z, Lu H, Mao Q, et al. Primary synovial sarcoma of the right heart involving the tricuspid valve in an elderly Chinese woman: a case report. Diagn Pathol. 2015; 10:80 [PubMed] Article available free on PMC after 01/04/2017 Related Publications
Described herein is a 51-year-old woman with abdominal discomfort who was found to have a pericardial effusion and a large mass in her right heart by computed tomography scan and who then underwent tumour resection surgery. The tumour was so extensive that it involved the right atrium, the right ventricle and the tricuspid valve, and encompassed the right coronary artery. The patient had no significant medical history, and no tumour was found at any other site. The morphology of the tumour mimicked carcinosarcoma, exhibiting mixed epithelioid and spindle elements and it was difficult to differentiate the diagnosis even by immunohistochemical stains. Then, the final diagnosis of primary biphasic synovial sarcoma of the heart was established based on the finding of SS18 rearrangement. This is a highly intriguing rare case that may represent a diagnostic pitfall, particularly regarding frozen section. The patient will receive chemotherapy, and we will pursue follow-up.
Tajima S, Takahashi T, Itaya T, et al. Cystic synovial sarcoma of the pleura mimicking a cystic thymoma: a case report illustrating the role of decreased INI-1 expression in differential diagnosis. Int J Clin Exp Pathol. 2015; 8(3):3262-9 [PubMed] Article available free on PMC after 01/04/2017 Related Publications
Less than 40 cases of primary pleural synovial sarcoma (SS) have been reported to date. Furthermore, only three cases of cystic SS have been documented in the English literature, including cases originating from sites other than the pleura. Herein, we present an exceedingly rare case of cystic SS originating from the mediastinal side of the visceral pleura in an asymptomatic 47-year-old man, which was detected during a checkup. On contrast-enhanced computed tomography, distinguishing between cystic SS and cystic thymoma was difficult because the tumor was attached to the anterior mediastinum where the latter type of malignancy is more often detected. Histopathological examination showed tumor cells with spindled morphology showing hypercellularity and moderate nuclear atypia, with less than one mitotic figure per high-power field. As these features are associated with both monophasic fibrous SS and type A thymoma, more data was required to determine proper diagnosis, and therefore, immunohistochemistry was performed. Along with a conventional panel of markers, the SS-specific marker integrase interactor 1 (INI-1) was applied and found to be decreased; decreased expression of INI-1 is characteristic of SS. A diagnosis of SS was confirmed by detection of the SYT-SSX fusion gene via fluorescence in situ hybridization. Given the relatively common availability of INI-1 testing in departments of pathology, this protein would be helpful incorporated into the standard panel of markers for diagnosing SS.
Mikami T, Kurose A, Javed F, Takeda Y 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. J Oral Maxillofac Surg. 2015; 73(8):1505-15 [PubMed] Related Publications
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.
Maekura T, Shimizu S, Kawaguchi T, et al. Intravascular synovial sarcoma of the pulmonary artery with massive pleural effusion: report of a case with a favorable response to Ifosfamide chemotherapy and palliative radiation therapy. Intern Med. 2015; 54(9):1095-8 [PubMed] Related Publications
Synovial sarcoma (SS) commonly arises in the para-articular soft tissue; however, very few cases of intravascular SS have so far been reported. We herein describe a case of pulmonary artery SS with massive pleural effusion. A biopsy of the pleural lesions showed uniform short spindle cell proliferation, while the SYT-SSX fusion gene, which is preceded by chromosomal translocation t(X;18)(p11;q11), was detected using reverse transcription-polymerase chain reaction. Treatment with ifosfamide chemotherapy and palliative radiation therapy was effective in reducing the growth of the tumor in the pulmonary artery and pleural lesions, indicating that this regimen may be useful for the treatment of unresectable SS in the pulmonary artery.
Leow WQ, Sng I Sinonasal haemangiopericytoma: histomorphology and differential diagnoses. Malays J Pathol. 2015; 37(1):53-6 [PubMed] Related Publications
A 39-year-old female presented with a fleshy nasal polyp occluding the left nasal cavity, associated with haemopurulent discharge. Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) scans of the paranasal cavities revealed a large polypoid tumour arising from the left middle turbinate and obstructing the left maxillary sinus ostium. However, no bony or intracranial involvement was identified. A biopsy revealed a tumour with small blue round cell morphology. The tumour cells showed diffuse strong membranous CD99 positivity and patchy CD34 positivity. Ancillary cytogenetic tests for the EWSR1 and SS18/SYT gene translocations were negative. In view of the non-invasive nature of the tumour and the low cell proliferative index (Ki-67) of 5%, a medial maxillectomy resection was performed. The resection revealed additional areas with spindle-cell morphology and focal haemangiopericytic vasculature. The tumour continued to show immunoreactivity to CD99 and CD34, as well as Smooth Muscle Actin (SMA) and Muscle Specific Actin (MSA). The overall findings are in keeping with a sinonasal haemangiopericytoma. With clear surgical resection margins, the patient is on routine follow-up and is currently disease-free.
Hirose M, Mizuno K, Kamisawa H, et al. Clear cell sarcoma of the kidney distinguished from synovial sarcoma using genetic analysis: a case report. BMC Res Notes. 2015; 8:129 [PubMed] Article available free on PMC after 01/04/2017 Related Publications
BACKGROUND: The most common pediatric renal neoplasm is Wilms tumor, but clear cell sarcoma of the kidney or synovial sarcoma of the kidney are also sometimes encountered. Accurate pathological diagnosis is important, because adjuvant therapies including chemotherapy and radiotherapy differ according to the pathological type. CASE PRESENTATION: A 9-year-old boy presented with a headache, and ultrasonography, computed tomography, and magnetic resonance imaging revealed a heterogeneous enhancement of soft tissue originating from the upper pole of the left kidney, measuring approximately 11.0 × 10.0 × 8.0 cm. A left radical nephrectomy was performed using an intraperitoneal approach through an anterior subcostal incision. Pathological examination suggested clear cell sarcoma of the kidney or synovial sarcoma of the kidney based on morphological and immunohistological features. Using genetic analysis, a final diagnosis of spindle cell pattern clear cell sarcoma of the kidney was made based on the absence of the SYT-SSX fusion gene. After adjuvant chemo-radiotherapy was administered, no recurrence or metastasis has been identified as of 60 months postoperatively. CONCLUSION: In this case, it was difficult to discriminate clear cell sarcoma of the kidney from synovial sarcoma of the kidney based on histopathological examination alone, and genetic analysis was required. Accurate pathological diagnosis of pediatric renal tumor is important for determining optimal treatment and preventing recurrence and metastasis.
Soon GS, Petersson F Beware of immunohistochemistry--report of a cytokeratin-, desmin- and INI-1-negative pelvic desmoplastic small round cell tumor in a 51 year old woman. Int J Clin Exp Pathol. 2015; 8(1):973-82 [PubMed] Article available free on PMC after 01/04/2017 Related Publications
We present a 51 year old female patient with a pelvic desmoplastic small round cell tumor with an unusual immunohistochemical profile, including absence of significant cytokeratin expression, complete negativity for desmin and widespread loss of nuclear INI-1 expression (>90% of tumor cells). The neoplastic cells were positive for epithelial membrane antigen (EMA), vimentin, and WT-1 (antibody against the C-terminus). The tumor showed classic histopathological features with no rhabdoid cells. Fluorescent in situ hybridization revealed EWSR1 gene rearrangement and absent SYT gene rearrangement. Reverse transcriptase polymerase chain reaction showed presence of EWSR1-WT1 transcript.
Nielsen TO, Poulin NM, Ladanyi M Synovial sarcoma: recent discoveries as a roadmap to new avenues for therapy. Cancer Discov. 2015; 5(2):124-34 [PubMed] Article available free on PMC after 01/04/2017 Related Publications
UNLABELLED: Oncogenesis in synovial sarcoma is driven by the chromosomal translocation t(X,18; p11,q11), which generates an in-frame fusion of the SWI/SNF subunit SS18 to the C-terminal repression domains of SSX1 or SSX2. Proteomic studies have identified an integral role of SS18-SSX in the SWI/SNF complex, and provide new evidence for mistargeting of polycomb repression in synovial sarcoma. Two recent in vivo studies are highlighted, providing additional support for the importance of WNT signaling in synovial sarcoma: One used a conditional mouse model in which knockout of β-catenin prevents tumor formation, and the other used a small-molecule inhibitor of β-catenin in xenograft models. SIGNIFICANCE: Synovial sarcoma appears to arise from still poorly characterized immature mesenchymal progenitor cells through the action of its primary oncogenic driver, the SS18-SSX fusion gene, which encodes a multifaceted disruptor of epigenetic control. The effects of SS18-SSX on polycomb-mediated gene repression and SWI/SNF chromatin remodeling have recently come into focus and may offer new insights into the basic function of these processes. A central role for deregulation of WNT-β-catenin signaling in synovial sarcoma has also been strengthened by recent in vivo studies. These new insights into the the biology of synovial sarcoma are guiding novel preclinical and clinical studies in this aggressive cancer.
Palmerini E, Benassi MS, Quattrini I, et al. Prognostic and predictive role of CXCR4, IGF-1R and Ezrin expression in localized synovial sarcoma: is chemotaxis important to tumor response? Orphanet J Rare Dis. 2015; 10:6 [PubMed] Article available free on PMC after 01/04/2017 Related Publications
BACKGROUND: Synovial sarcoma (SS) is a rare tumor, with dismal survival when metastatic. The role of adjuvant chemotherapy is debated. New prognostic and predictive factors are needed. METHODS: We reviewed patients with localized SS; SS18-SSX fusion transcript presence was confirmed by FISH and RT-PCR. Expression of CXCR4, IGF-1R and Ezrin were evaluated by immunohistochemistry. RESULTS: Tumor samples from 88 SS patients (45 female; 43 male) with median age 37 years (range 11-63) were selected. The size of the lesion was > 5 cm in 68% of patients and 34% of cases presented biphasic histotype. All patients underwent surgery, 56% adjuvant radiotherapy (RT), 65% adjuvant chemotherapy. A positive stain for IGF-1R was detected in 55 patients, with nucleus expression in 21 patients. CXCR4 was expressed in 74 patients, nuclear pattern in 31 patients. 80 SS were positive to Ezrin, 48 had cytoplasmatic location, 32 membrane location. With a median follow-up of 6 years (1-30 years), the 5-year overall survival (OS) was 70% (95% CI 60-81). 5-year OS was 63% (95% CI 41-85%) for patients with positive IGF-1R/nuclear expression, and 73% (95% CI 61-85%; P = 0.05) in negative patients. 5-year OS was 47% (95% CI 27-66%) in patients with positive CXCR4/nuclear staining, and 86% (95% CI 76-96%, P = 0.0003) in negative cases. No survival difference was found according to Ezrin expression. By multivariate analysis, nuclear expression of CXCR4 and IGF-1R was confirmed independent adverse prognostic factor for SS patient survival linked to the use of chemotherapy. CONCLUSIONS: Our findings have important potential implications demonstrating that together with clinical prognostic factors such as radiotherapy and age, CXCR4 and IGF-1R negatively influences survival in patients with localized SS. We believe that further studies addressed to the effects of CXCR4 and IGF-1R inhibitors on cell viability and function are needed to plan new and more appropriate SS treatments.
Becerikli M, Wieczorek S, Stricker I, et al. Numerical and structural chromosomal anomalies in undifferentiated pleomorphic sarcoma. Anticancer Res. 2014; 34(12):7119-27 [PubMed] Related Publications
BACKGROUND: Malignant fibrous histiocytoma (MFH) or undifferentiated pleomorphic sarcoma (UPS) is the most common soft-tissue sarcoma of late adult life. Further advances in genetic characterization are warranted. The aim of this study was to search for numerical and structural chromosomal anomalies in UPS. MATERIALS AND METHODS: We investigated five sarcoma-specific chromosomal translocations, five oncogene amplifications as well as the numerical karyotype of 19 UPS samples and one UPS/MFH cell line (U2197) using FISH probes on interphase nuclei. RESULTS: Our results demonstrate that chromosomal translocations involving CHOP, SYT, EWS, FUS and FKHR genes are absent. Furthermore, amplification of ERBB2 (10.5%) and MDM2 (10.5%) was observed whereas the EGFR, C-MYC and N-MYC genes were not amplified. Interestingly, predominant aneuploidies were found in eight chromosomes. CONCLUSION: The data demonstrate rarity of sarcoma-specific chromosomal breaks and oncogene amplifications in UPS, yet polysomic chromosomes appear more characteristically in this condition.
Horn H, Allmanritter J, Doglioni C, et al. Fluorescence in situ analysis of soft tissue tumor associated genetic alterations in formalin-fixed paraffin-embedded tissue. Pathol Res Pract. 2014; 210(12):804-11 [PubMed] Related Publications
No prospective studies are available to date evaluating the combined analysis of chromosomal alterations via interphase FISH in different soft tissue sarcoma (STS) subtypes. We tested 64 consecutive sarcoma specimens with FISH probes to detect aberrations specific for a given STS subtype. We first determined the translocation frequency in the specific STS subtypes in 48 tumors, with the primary pathological diagnosis as the gold standard. Subsequently, to evaluate sensitivity and specificity, all FISH probes were hybridized to 16 STS of hitherto unknown diagnosis. DDIT3 translocations occurred in 8/10 (80%) of myxoid liposarcomas. FOXO1 translocations were noted in 4/4 (100%) of alveolar but in none of 7 embryonal rhabdomyosarcomas. All 15 (100%) Ewing sarcomas/PNET and 4 clear cell sarcomas (4/4) harbored EWSR1 translocations. SS18 rearrangements were demonstrated in 8/9 (89%) synovial sarcomas. MDM2 amplification was noted in 7/8 (88%) atypical lipomatous tumors/well-differentiated and 3/3 (100%) dedifferentiated liposarcomas, respectively, but not in four pleomorphic liposarcomas. Sensitivities and specificities ranged from 80% to 100% and from 93% to 100%, respectively, with the highest values observed for FOXO1 (100% each). We conclude, therefore, that is possible to accurately predict the STS subtype using a panel of different subtype-specific FISH probes, thereby greatly facilitating the differential diagnosis of these tumors.
Yang J, Annala M, Ji P, et al. Recurrent LRP1-SNRNP25 and KCNMB4-CCND3 fusion genes promote tumor cell motility in human osteosarcoma. J Hematol Oncol. 2014; 7:76 [PubMed] Article available free on PMC after 01/04/2017 Related Publications
BACKGROUND: The identification of fusion genes such as SYT-SSX1/SSX2, PAX3-FOXO1, TPM3/TPM4-ALK and EWS-FLI1 in human sarcomas has provided important insight into the diagnosis and targeted therapy of sarcomas. No recurrent fusion has been reported in human osteosarcoma. METHODS: Transcriptome sequencing was used to characterize the gene fusions and mutations in 11 human osteosarcomas. RESULTS: Nine of 11 samples were found to harbor genetic inactivating alterations in the TP53 pathway. Two recurrent fusion genes associated with the 12q locus, LRP1-SNRNP25 and KCNMB4-CCND3, were identified and validated by RT-PCR, Sanger sequencing and fluorescence in situ hybridization, and were found to be osteosarcoma specific in a validation cohort of 240 other sarcomas. Expression of LRP1-SNRNP25 fusion gene promoted SAOS-2 osteosarcoma cell migration and invasion. Expression of KCNMB4-CCND3 fusion gene promoted SAOS-2 cell migration. CONCLUSIONS: Our study represents the first whole transcriptome analysis of untreated human osteosarcoma. Our discovery of two osteosarcoma specific fusion genes associated with osteosarcoma cellular motility highlights the heterogeneity of osteosarcoma and provides opportunities for new treatment modalities.
Minami Y, Kohsaka S, Tsuda M, et al. SS18-SSX-regulated miR-17 promotes tumor growth of synovial sarcoma by inhibiting p21WAF1/CIP1. Cancer Sci. 2014; 105(9):1152-9 [PubMed] Article available free on PMC after 01/04/2017 Related Publications
MicroRNA (miRNA) can function as tumor suppressors or oncogenes, and also as potential specific cancer biomarkers; however, there are few published studies on miRNA in synovial sarcomas, and their function remains unclear. We transfected the OncomiR miRNA Precursor Virus Library into synovial sarcoma Fuji cells followed by a colony formation assay to identify miRNAs to confer an aggressive tumorigenicity, and identified miR-17-5p from the large colonies. MiR-17 was found to be induced by a chimeric oncoprotein SS18-SSX specific for synovial sarcoma, and all examined cases of human synovial sarcoma expressed miR-17, even at high levels in several cases. Overexpression of miR-17 in synovial sarcoma cells, Fuji and HS-SYII, increased colony forming ability in addition to cell growth, but not cell motility and invasion. Tumor volume formed in mice in vivo was significantly increased by miR-17 overexpression with a marked increase of MIB-1 index. According to PicTar and Miranda algorithms, which predicted CDKN1A (p21) as a putative target of miR-17, a luciferase assay was performed and revealed that miR-17 directly targets the 3'-UTR of p21 mRNA. Indeed, p21 protein level was remarkably decreased by miR-17 overexpression in a p53-independent manner. It is noteworthy that miR-17 succeeded in suppressing doxorubicin-evoked higher expression of p21 and conferred the drug resistance. Meanwhile, introduction of anti-miR-17 in Fuji and HS-SYII cells significantly decreased cell growth, consistent with rescued expression of p21. Taken together, miR-17 promotes the tumor growth of synovial sarcomas by post-transcriptional suppression of p21, which may be amenable to innovative therapeutic targeting in synovial sarcoma.
Wakamatsu T, Naka N, Sasagawa S, et al. Deflection of vascular endothelial growth factor action by SS18-SSX and composite vascular endothelial growth factor- and chemokine (C-X-C motif) receptor 4-targeted therapy in synovial sarcoma. Cancer Sci. 2014; 105(9):1124-34 [PubMed] Article available free on PMC after 01/04/2017 Related Publications
Synovial sarcoma (SS) is a malignant soft-tissue tumor characterized by the recurrent chromosomal translocation SS18-SSX. Vascular endothelial growth factor (VEGF)-targeting anti-angiogenic therapy has been approved for soft-tissue sarcoma, including SS; however, the mechanism underlying the VEGF signal for sarcomagenesis in SS is unclear. Here, we show that SS18-SSX directs the VEGF signal outcome to cellular growth from differentiation. Synovial sarcoma cells secrete large amounts of VEGF under spheroid culture conditions in autocrine fashion. SS18-SSX knockdown altered the VEGF signaling outcome, from proliferation to tubular differentiation, without affecting VEGF secretion, suggesting that VEGF signaling promoted cell growth in the presence of SS18-SSX. Thus, VEGF inhibitors blocked both host angiogenesis and spheroid growth. Simultaneous treatment with VEGF and chemokine (C-X-C motif) (CXC) ligand 12 and CXC receptor 4 inhibitors and/or ifosfamide effectively suppressed tumor growth both in vitro and in vivo. SS18-SSX directs the VEGF signal outcome from endothelial differentiation to spheroid growth, and VEGF and CXC receptor 4 are critical therapeutic targets for SS.
Kimura H, Yamamoto N, Nishida H, et al. Synovial sarcoma in knee joint, mimicking low-grade sarcoma confirmed by molecular detection of SYT gene split. Anticancer Res. 2014; 34(6):3105-11 [PubMed] Related Publications
A 10-year-old boy underwent arthroscopic curettage for an intra-articular mass in knee joint. The tumor was diagnosed as low-grade fibrous sarcoma. Five years later, the patient presented with a recurrent tumor. The patient underwent a marginal excision with knee joint preservation and without adjuvant therapy. Two years after the last surgery, the patient is thriving with no evidence of recurrent or metastatic disease. The final diagnosis was synovial sarcoma confirmed via a SYT gene split performed with fluorescent in situ hybridization (FISH), although the tumor appeared as a low-grade fibrous type in a hematoxylin-eosin section. The first curetted specimen was also confirmed to bear a SYT gene split. Synovial sarcoma has been conventionally recognized as a high-grade sarcoma. Our patient had a tumor that exhibited the characteristics of both a histologically and clinically low-grade tumor. From the present case, we consider that low-grade variants of synovial sarcoma do exist although their existence remains controversial.
de Souza RR, Oliveira ID, del Giúdice Paniago M, et al. Investigation of IGF2, Hedgehog and fusion gene expression profiles in pediatric sarcomas. Growth Horm IGF Res. 2014; 24(4):130-6 [PubMed] Related Publications
UNLABELLED: The childhood sarcomas are malignant tumors with high mortality rates. They are divided into two genetic categories: a category without distinct pattern karyotypic changes and the other category showing unique translocations that originate gene rearrangements. This category includes rhabdomyosarcoma (RMS), Ewing's sarcoma (ES) and synovial sarcoma (SS). Diverse studies have related development genes, such as; IGF2, IHH, PTCH1 and GLI1 and sarcomatogenesis. OBJECTIVE: To characterize the RMS, ES and SS rearrangements, we quantify the expression of IGF2 IHH, PTCH1 and GLI1 genes and correlate molecular data with clinical parameters of patients. DESIGN: We analyzed 29 RMS, 10 SS and 60 ES tumor samples by RT-PCR (polymerase chain reaction-reverse transcription) and qPCR (quantitative PCR). RESULTS: Among the samples of ARMS, 50% had rearrangements of PAX3/7-FOXO1, 60% of ES samples were EWS-FLI1 positive and 90% of SS samples were positive for SS18-SSX1/2. In relation to the control reference samples (QPCR Human Reference Total RNA-Stratagene, Human Skeletal Muscle Total RNA-Ambion, Universal RNA Human Normal Tissues-Ambion), RMS samples showed a high IGF2 gene expression (p<0.0001). Moreover, ES samples showed a low IGF2 gene expression (p<0.0001) and high IHH (p<0.0001), PTCH1 (p=0.0173) and GLI1 (p=0.0113) gene expressions. CONCLUSIONS: The molecular characterization of IGF and Hedgehog pathway in these pediatric sarcomas may collaborate to enable a better understanding of the biological behavior of these neoplasms.
Ohzeki M, Fujita S, Miyazaki H, et al. A patient with primary pericardial synovial sarcoma who presented with cardiac tamponade: a case report and review of the literature. Intern Med. 2014; 53(6):595-601 [PubMed] Related Publications
A 36-year-old man presented with near-syncope. He was found to have massive pericardial effusion with a giant pericardial tumorous lesion. The pericardial effusion exhibited a bloody nature; however, neither malignant cells nor infectious organisms were detected. (18)F-fluorodeoxyglucose-positron emission tomography (FDG-PET) showed an increased uptake of FDG in the pericardial tumor only. Although the tumor was not resectable, thoracotomy and tissue sampling were performed. A histological analysis showed CD99 positivity and SYT gene rearrangement, leading to a diagnosis of synovial sarcoma arising from the left lateral pericardial surface. The patient is now receiving chemotherapy.
Crew AJ, Clark J, Fisher C, et al. Fusion of SYT to two genes, SSX1 and SSX2, encoding proteins with homology to the Kruppel-associated box in human synovial sarcoma. EMBO J. 1995; 14(10):2333-40 [PubMed] Article available free on PMC after 01/04/2017 Related Publications
We demonstrate that the cytogenetically defined translocation t(X;18)(p11.2;q11.2) found in human synovial sarcoma results in the fusion of the chromosome 18 SYT gene to either of two distinct genes, SSX1 or SSX2, at Xp11.2. The SSX1 and SSX2 genes encode closely related proteins (81% identity) of 188 amino acids that are rich in charged amino acids. The N-terminal portion of each SSX protein exhibits homology to the Kruppel-associated box (KRAB), a transcriptional repressor domain previously found only in Kruppel-type zinc finger proteins. PCR analysis demonstrates the presence of SYT-SSX1 or SYT-SSX2 fusion transcripts in 29 of 32 of the synovial sarcomas examined, indicating that the detection of these hybrid transcripts by PCR may represent a very useful diagnostic method. Sequence analysis has demonstrated heterogeneity in the fusion transcripts with the formation of two distinct SYT-SSX1 fusion junctions and two distinct SYT-SSX2 fusion junctions.
de Leeuw B, Balemans M, Olde Weghuis D, Geurts van Kessel A Identification of two alternative fusion genes, SYT-SSX1 and SYT-SSX2, in t(X;18)(p11.2;q11.2)-positive synovial sarcomas. Hum Mol Genet. 1995; 4(6):1097-9 [PubMed] Related Publications
Kawai A, Woodruff J, Healey JH, et al. SYT-SSX gene fusion as a determinant of morphology and prognosis in synovial sarcoma. N Engl J Med. 1998; 338(3):153-60 [PubMed] Related Publications
BACKGROUND: Synovial sarcomas account for up to 10 percent of soft-tissue sarcomas and include two major histologic subtypes, biphasic and monophasic, defined respectively by the presence and absence of glandular epithelial differentiation in a background of spindle tumor cells. A characteristic SYT-SSX fusion gene resulting from the chromosomal translocation t(X;18)(p11;q11) is detectable in almost all synovial sarcomas. The translocation fuses the SYT gene from chromosome 18 to either of two highly homologous genes at Xp11, SSX1 or SSX2. SYT-SSX1 and SYT-SSX2 are thought to tunction as aberrant transcriptional regulators. We attempted to determine the influence of the two alternative forms of the SYT-SSX fusion gene on tumor morphology and clinical outcome in patients with this sarcoma. METHODS: We analyzed SYT-SSX fusion transcripts in 45 synovial sarcomas (33 monophasic and 12 biphasic) by the reverse-transcriptase polymerase chain reaction and compared the results with relevant clinical and pathological data. RESULTS: The SYT-SSX1 and SYT-SSX2 fusion transcripts were detected in 29 (64 percent) and 16 (36 percent) of the tumors, respectively. There was a significant relation (P=0.003) between histologic subtype (monophasic vs. biphasic) and SSX1 or SSX2 involvement in the fusion transcript: all 12 biphasic synovial sarcomas had a SYT-SSX1 fusion transcript, and all 16 tumors that were positive for SYT-SSX2 were monophasic. Kaplan-Meier analysis of 39 patients with localized tumors showed that the 15 patients with SYT-SSX2 had significantly better metastasis-free survival than the 24 patients with SYT-SSX1 (P=0.03 by multivariate analysis; relative risk, 3.0). There were no significant correlations between the type of SYT-SSX transcript and age, sex, tumor location and size, whether there were metastases at diagnosis, or whether patients underwent chemotherapy. Histologic subtype alone was not prognostically important. CONCLUSIONS: The type of SYT-SSX fusion transcript correlates with both the histologic subtype and the clinical behavior of synovial sarcoma. SYT-SSX fusion transcripts are a defining diagnostic marker of synovial sarcomas and may also yield important independent prognostic information.