滑膜肉瘤石蜡包埋组织SYT-SSX融合基因检测的临床病理意义

目的：探讨在石蜡包埋组织中检测SYT－SSX融合基因的可行性及其对滑膜肉瘤的诊断,分型和鉴别诊断的价值。方法：收集滑膜肉瘤标本38例,以恶性周围神经鞘膜瘤,纤维肉瘤,平滑肌肉瘤,尤文肉瘤,血管外皮肉瘤和转移性腺癌作为对照,共40例,均为甲醛固定,石蜡包埋组织,用逆转录－聚合酶链反应（RT－PCR）方法检测SYT－SSX融合基因mRNA表达,以看家基因PBGD作为内对照检测mRNA质量。结果：78例标本中64例（占82．1％）可检出PBGD mRNA表达,38例滑膜肉瘤中33例中可检出SYT－SSX融合基因mRNA表达,对照组无一例检出SYT－SSX基因,去除PBGD及SYT－SSX均阴性病例1例,滑膜肉瘤SYT－SSX融合基因检出率为89．2％（33／37）,33例SYT－SSX阳性滑膜肉中,SYT－SSX1型22例,SYT－SSX2型6例,5例无法区分。融合基因类型与滑膜肉瘤组织学类型有关。10例双相型滑膜肉瘤均为SYT－SSX1型,而18例单相型滑膜肉瘤中SYT－SSX1型12例,SYT－SSX2型6例,二者差异有统计学意义（P＜0．05）,结论：（1）从石蜡包埋组织中检测SYT－SSX融合基因对滑膜肉瘤有较高的敏感性和特异性,可用于滑膜肉瘤的诊断和鉴别诊断;（2）SYT－SSX融合基因类型与滑膜肉瘤组织学类型相关,SYT－SSX2型仅见于单相型。     

Aberrant expression of tight junction-related proteins ZO-1, claudin-1 and occludin in synovial sarcoma: an immunohistochemical study with ultrastructural correlation.

Synovial sarcoma demonstrates epithelial differentiation, either by light microscopy (biphasic synovial sarcoma) or by immunohistochemical/ultrastructural methods only (monophasic) and poorly differentiated synovial sarcoma. Although the glands of synovial sarcoma are known to have tight junction-like structures, far less is known about junction formation in the spindled component of synovial sarcomas. Additionally, it is unknown whether the tight junctions of synovial sarcoma are normally constituted. The tight junction is a multiprotein complex consisting of numerous proteins that include ZO-1, claudin-1 and occludin. A total of 35 cases of synovial sarcoma (13 biphasic, 14 monophasic and eight poorly differentiated) were immunostained for ZO-1, claudin-1 and occludin using commercially available antibodies, heat-induced epitope retrieval and standard avidin-biotin technique. When available, corresponding electron micrographs were reviewed. For five cases, the presence of either an SYT-SSX1 (three cases) or SYT-SSX2 (two cases) gene fusion was known. Positive cases showed particulate membrane staining. The glands of biphasic synovial sarcomas expressed ZO-1 (13/13), claudin-1 (12/13) and occludin (11/13) in a manner identical to normal glandular epithelia, at the apical portion of the lateral membrane. The spindle cells of biphasic synovial sarcomas showed abnormal circumferential membranous expression of ZO-1 (12/13), claudin-1 (6/13) and occludin (3/13). Monophasic synovial sarcomas expressed ZO-1 in a circumferential pattern (13/14) but less often claudin-1 (4/14) or occludin (3/14). Poorly differentiated synovial sarcomas expressed ZO-1 (8/8) and claudin-1 (6/8) but only rarely occludin (2/8). By electron microscopy, recognizable tight junctions were seen only in glands. No correlation was seen between histologic subtype or fusion type and expression of tight junction proteins. We conclude that the glands of biphasic synovial sarcomas show well-organized, true epithelial tight junctions. In contrast, the spindled cells of all synovial sarcomas show significant abnormalities in the expression and localization of tight junction proteins, suggesting partial and/or aberrant epithelial differentiation.     

滑膜肉瘤的融合基因检测分析

目的：基于存在染色体易位所致特异的SYT－SSX融合基因,证实可在滑膜肉瘤组织石蜡切片上检测出并探讨其在诊断中的价值。方法：采用逆转录－聚合酶链反应,检测并分析20例滑膜肉瘤（组织学亚型15例单相,5例双相）的SYT－SSX转录物,并对照相应病理学所见,结果：所检20例滑膜肉瘤中,有19例（95％）出现特异SYT－SSX逆转录聚酶链反应产物,其中13例具有SYT－SSX2融合基因的肿瘤有10例呈组织学单相分化。结论：SYT－SSX融合基因转录物可在石蜡切片和组织块中获得满意结果。具有较好的灵敏性,是滑膜肉瘤所特有的诊断标志物,它的亚类分型（SYT－SSX1和SYT－SSX2）,可能成为预后推测指征。     

Dual colour fluorescence in situ hybridization to paraffin-embedded samples to deduce the presence of the der(X)t(X;18)(p11.2;q11.2) and involvement of either the SSX1 or SSX2 gene: a diagnostic and prognostic aid for synovial sarcoma

Identification of the t(X;18)(p11.2;q11.2) and the fusion gene products, SYT–SSX1 and SYT–SSX2, associated with a high proportion of synovial sarcomas, has been shown to be a useful diagnostic aid. This study demonstrates the application of dual colour fluorescence in situ hybridization to paraffin-embedded samples to deduce the presence of the derivative X chromosome and also the position of the breakpoint on chromosome X at either the SSX1 or the SSX2 gene. This used region specific markers from chromosomes X and 18 and an optimized protocol involving microwave exposure. Novel and rapid scoring criteria were validated which circumvented potential problems of nuclear truncation and defining cell boundaries. This involved blind analysis of two negative sarcoma samples and three synovial sarcomas in which corresponding frozen material had been previously shown to have the translocation involving different SSX genes. Six new cases diagnosed as synovial sarcoma were also analysed; two monophasic and two biphasic case were deduced to have a breakpoint in the SSX1 gene, one monophasic case an SSX2 breakpoint, and one case did not show rearrangement of the region. The ability to analyse formalin-fixed, paraffin-embedded samples in this way has practical implications for aiding the diagnosis of difficult cases, recently ascribed prognostic relevance, and allows further retrospective studies to be carried out. The methodology is also applicable to the identification of other tumour specific translocations in paraffin-embedded material. Copyright © 1999 John Wiley & Sons, Ltd.     

34例滑膜肉瘤分子遗传学改变的诊断学意义

目的 探讨石蜡包埋滑膜肉瘤组织中t(x；18)(p11．2；q11．2)染色体易位融合基因SYT-SSX mRNA表达的诊断学意义和应用价值。方法 收集滑膜肉瘤标本34例，以14例梭形细胞肉瘤和小圆细胞肉瘤做对照(包括2例纤维肉瘤、2例平滑肌肉瘤、1例恶性神经鞘膜瘤、4例Ewing肉瘤、2例腺泡型横纹肌肉瘤、2例恶性黑色素瘤、1例血管外皮瘤)。在进行免疫组织化学指标检测的基础上，用一步法逆转录-聚合酶链反应(RT-PCR)技术检测34例石蜡包埋滑膜肉瘤组织中SYT-SSX的表达。结果 34例滑膜肉瘤中30例获得有效RNA，28例(93．3％)检出SYT-SSX融合基因表达。其中14例表达SYT-SSXl型者中10例为双相型，9例表达SYT-SSX2型者中5例为单相分化型，5例SYT-SSXl／2均未检出。对照组均未检出SYT-SSX基因的表达。结论 SYT-SSX融合基因表达可作为诊断滑膜肉瘤新的分子诊断指标。一步法RT-PCR是一种理想而可行的用于石蜡包埋滑膜肉瘤组织SYT-SSX融合基因检测的分子诊断技术。     

Synovial sarcoma (SS): new perspectives supported by modern technology

Based upon the experience of 256 cases of synovial sarcoma (SS), the present review analyzes structural, biological and molecular pathology of this poorly known sarcoma. The histology displays a multiphenotype with two major components: biphasic and monophasic SS. In addition, a number of variants have been described: undifferentiated Ewing's like, myoxid and predominantly epithelial (monophasic epithelial sarcoma). Microcalcifications and squamous metaplasia are often seen in the tumor. Immunohistochemistry with EMA and cytokeratin in the epithelial or epithelioid component is diagnostic for SS together with vimentin positivity in the spindle cells. Several other epitopes are also expressed (CD99, CD56, C-MET, HGF/SF, CD44). The ultrastructure confirms the variegated pattern of the neoplasm demonstrating the epithelial component and the epithelioid or spindle cell type closely associated with each other. Transition of epithelial cells to epithelioid and spindle-like mesenchymal component is seen. Nude-mice xenografts and cell lines after in vitro culture confirm heterogeneity of this sarcoma. Molecular histology of the SS has provided high utility not only for their differential diagnosis due to a specific chromosomal translocation: t(X;18)(p11.2;q11.2) but also after cloning these breakpoints resulting in the fusion of two genes: SYT at 18q11 and SSX at Xp11. Further observations have lead to distinguish the existence of two related genes: SSX1 and SSX2, that provide a highly specific and sensitive diagnostic marker for SS. Moreover, clinical correlations have demonstrated that SYT-SSX1 leads to a poor clinical outcome while the fusion SYT-SSX2 provides survival advantages to the patients.     

Immunostaining for SYT protein discriminates synovial sarcoma from other soft tissue tumors: analysis of 146 cases.

Synovial sarcoma in its classic biphasic form can be distinguished readily from other soft tissue lesions; however, monophasic and poorly differentiated forms are diagnostically more problematic. For this reason, we assessed the efficacy of immunostaining for SYT and SSX1 proteins, the gene products resulting from unique synovial sarcoma translocation, to distinguish synovial sarcoma from other soft tissue lesions. A total number of 146 cases were analyzed, including 47 synovial sarcoma cases (all of which were verified by FISH to have t(X; 18) translocation and SYT-SSX fusion gene) and 99 soft tissue tumors of various types. A polyclonal IgG antibody against SYT was used to stain formalin-fixed paraffin embedded tissues. Forty-one out of 47 (87%) synovial sarcoma displayed strong positive nuclear staining (ranging from 80 to 90% of the tumor cells) for SYT antibody. Nineteen of 99 (19%) non-synovial sarcoma cases showed variable nuclear and cytoplasmic staining with SYT, which ranged from 20 to 60% of tumor nuclei, and included malignant peripheral nerve sheath tumor (5/25), solitary fibrous tumor (2/14), Ewing sarcoma (2/6), low grade fibromyxoid tumor (2/4), extraskeletal mesenchymal chondrosarcoma (2/6), gastrointestinal tumor (4/17), epithelioid sarcoma (2/2). The remaining non-synovial sarcomas were negative. This is the first study demonstrating SYT protein expression in tissue sections of synovial sarcoma. This method could provide an easy, rapid and widely applicable means of assisting in the diagnosis of synovial sarcoma, particularly when material and/or resources are unavailable for PCR or FISH-based testing. However, as variable weak staining for SYT may be encountered in a small percentage of non-synovial sarcoma sarcomas, a positive interpretation should be made only when the staining is strong, nuclear and present in the majority of cells.     

Clinical importance of genomic imbalances in synovial sarcoma evaluated by comparative genomic hybridization

The t(X;18)(p11.2;q11.2) (SYT/SSX1 or SSX2) is represented in more than 95% of synovial sarcoma. Even if recent data has implicated that the type of fusion gene (SYT/SSX1 or SYT/SSX2) can be of prognostic importance, the cellular and molecular mechanisms underlying the clinical behavior of synovial sarcoma are still poorly understood. To approach this issue, we investigated whether secondary genetic aberrations may influence the clinical outcome of synovial sarcoma. Clinical outcome with reference to comparative genomic hybridization (CGH) findings (losses or gains of genetic material) were analyzed for a uniquely large modern material of 69 synovial sarcomas. Thirty-five of 69 specimens showed DNA sequence copy number changes. The frequency of aberrations/tumor were higher (mean 4.7) for monophasic tumors than for biphasic tumors (mean 2.1). Gains of the whole or parts, including the long arm, of chromosome 8 were significantly overrepresented in large tumors (> 5 cm), suggesting that tumors with this genetic abnormality have an increased growth rate. No difference regarding metastasis-free or overall survival was seen between patients with or without tumors containing secondary copy number changes. No specific copy number change was linked to a significantly improved or impaired metastasis-free survival.