Synovial sarcoma: ultrastructural and immunohistochemical features of epithelial differentiation in monophasic and biphasic tumors

Treatment of Primary Pulmonary Synovial Sarcoma in a Low-Resource Country: A Case Report

Primary synovial sarcoma of the lung is a rare malignant cancer. The symptoms are nonspecific; they may not appear at all, so it is often diagnosed in the late stages. Moreover, accurate diagnosis requires a combination of the results of clinical evaluation, imaging, and histological examinations, since the results of these methods separately are not very specific and may lead to misdiagnosis. Given the rarity of this diagnosis, the therapy is not standardized. The preferred treatment regimen involves surgery combined with neoadjuvant or adjuvant radio- and chemotherapy. This case report describes a 67-year-old male patient who was diagnosed with pulmonary synovial sarcoma. Diagnosis was confirmed via computed tomography (CT) imaging and immunohistochemical (IHC) examination. After surgical removal, the patient underwent adjuvant radiotherapy.

Ultrastructural differences between synovial sarcoma and solitary fibrous tumor: comparative study in adult patients from the National Cancer Institute of Mexico

Synovial sarcoma (SS) and solitary fibrous tumor (SFT) are entities with considerable morphological and immunohistochemical similarities that sometimes show a non-confirmatory profile (TLE1 negative, CD34 and focal or negative STAT6 and lack of specific fusion IHC markers), in which the utility ultrastructure is unknown. A cross-sectional, retrospective, analytical, nonexperimental study was carried out by the Department of Pathology of the National Cancer Institute of Mexico (INCan) e from January 1, 2009 to December 31, 2018. With 17 SFT cases with diffuse or focal CD34 and STAT6 positivity and 18 cases of SS with positive FISH molecular test t(X:18) breakapart were studied by electron microscopy of fresh glutaraldehyde fixed or paraffin-embedded tissue. The ultrastructural findings with a significant difference present in the SS were tandem tight junctions, desmosomes and abundance of dilated rough endoplasmic reticulum (RER) cisternae (p < 0.001, 0.003, and 0.001, respectively); while in the (SFT) the presence of abundant glycogen, basal lamina, long and slender cytoplasmic processes, pinocytic vesicles, hemidesmosomes, and/or dense plaques, collagen skein, and microvilli-like buds (p = 0.028, 0.005, and <0.001 for the last five). We then infer that the five distinctive markers of the SFT are the collagen skeins intermingled with cellular processes in a shape of "squid can," and the pinocytic vesicles as they were not observed in any case of SS. Conversely, tandem junctions were not found in any SFT case. Although the presence of multivesicular buds in the SFT was not significant, it had not been previously described.

A Practical Approach to Small Round Cell Tumors Involving the Gastrointestinal Tract and Abdomen

Small round cell neoplasms are diagnostically challenging owing to their clinical and pathologic overlap, necessitating use of large immunopanels and molecular analysis. Ewing sarcomas (ES) are the most common, but EWSR1 is translocated in several diverse neoplasms, some with round cell morphology. Molecular advances enable classification of many tumors previously termed 'atypical ES'. The current WHO Classification includes two new undifferentiated round cell sarcomas (with CIC or BCOR alterations), and a group of sarcomas in which EWSR1 partners with non-Ewing family transcription factor genes. This article reviews the spectrum of small round cell sarcomas within the gastrointestinal tract and abdomen.

Primary monophasic synovial sarcoma of the lung: Rare case report

Primary monophasic synovial sarcoma of the lung is an extremely rare malignant mesenchymal tumor that can develop at any anatomic site. Synovial sarcoma is considered a high grade tumor with a poor prognosis. Metastatic pulmonary sarcoma is much more common. Hence primary lesion elsewhere in the body needs exclusion. No clinical or radiological features are specific for pulmonary sarcoma, often it is confused with bronchogenic carcinoma. Therefore biopsy is needed to establish the diagnosis of this rare tumor. We hereby present two cases of histologically proven primary monophasic synovial sarcoma of lung. The imaging features of this rare disease is reviewed.

A Case of Poorly Differentiated Synovial Sarcoma Arising in a Nasal Cavity Radiation Field: An Unusual Tumor in an Unusual Location

Synovial sarcomas are high-grade soft tissue sarcomas of primitive mesenchymal origin which are defined by a pathognomonic t(X;18)(p11,q11) translocation, and which occur in pediatric and adult populations. Herein we report a case of a 33-year-old female with a history of nasopharyngeal carcinoma status post radiotherapy, presenting with a poorly differentiated synovial sarcoma of the nasal cavity arising in the radiation field. While the development of radiation-associated sarcoma is a known complication of radiotherapy, to date only 10 cases of synovial sarcoma have been reported to occur in previously irradiated tissues. Moreover, only 1 case of poorly differentiated synovial sarcoma involving the nasopharynx has been described.

Primary Intraosseous Synovial Sarcoma in the Mandible

Synovial sarcoma (SS) is a rare malignant mesenchymal tumor that mainly occurs in body extremities, being uncommon in the head and neck region. In the present study, we described a case of primary intraosseous SS arising in the mandible of a 22-year-old young male. The patient reported a painful swelling on the left side of the mandible for the last 7 months. Imaging exams showed the presence of an expansive and multilocular radiolucent lesion, extending from the left condyle to the mandibular body. The clinic diagnostic hypotheses were ameloblastoma or malignant neoplasm. Histologically, the lesion was characterized by a proliferation of spindle cells exhibiting vesicular nuclei and evident nucleolus. Neoplastic cells were positive for AE1/AE3, cytokeratin 7, vimentin, CD-99, and TLE-1 and negative for CD-34, S-100, SMA, and HHF-35. A combination of clinical, histologic, and immunohistochemical characteristics supported the diagnosis of SS. The patient was referred for treatment, and preoperative exams did not reveal any other tumor foci in the body of the patient. The final diagnosis was of a primary intraosseous SS of the mandible.

The Biology of Synovial Sarcoma: State-of-the-Art and Future Perspectives

New molecular insights are being achieved in synovial sarcoma (SS) that can provide new potential diagnostic and prognostic markers as well as therapeutic targets. In particular, the advancement of research on epigenomics and gene regulation is promising. The concrete hypothesis that the pathogenesis of SS might mainly depend on the disruption of the balance of the complex interaction between epigenomic regulatory complexes and the consequences on gene expression opens interesting new perspectives. The standard of care for primary SS is wide surgical resection combined with radiation in selected cases. The role of chemotherapy is still under refinement and can be considered in patients at high risk of metastasis or in those with advanced disease. Cytotoxic chemotherapy (anthracyclines, ifosfamide, trabectedin, and pazopanib) is the treatment of choice, despite several possible side effects. Many possible drug-able targets have been identified. However, the impact of these strategies in improving SS outcome is still limited, thus making current and future research strongly needed to improve the survival of patients with SS.

Primary synovial sarcomas in the paediatric and young adult population: A pictorial review

PURPOSE

To present a pictorial essay of paediatric primary synovial sarcomas from common and less documented anatomical locations. To review the literature for the imaging characteristics and prognostic factors of this rare but important childhood malignancy.

METHOD

24 primary synovial sarcoma cases (17 male, 7 female with an age range 4-21 years) were reviewed in a collaborative effort between St Jude Children's Research Hospital and Great Ormond Street Hospital for Children. Images from 19 cases were selected for inclusion, to demonstrate the spectrum of appearances across imaging modalities, in a range of different anatomical locations (upper limb, lower limb, chest/abdomen/pelvis, and head and neck). A literature review depicting the typical radiological features and the prognostic significance of these features, was also conducted.

RESULTS AND CONCLUSIONS

Primary synovial sarcoma can occur in any anatomical location, but typically within the extremities and often in close association with joints. Rarer anatomical locations described in our essay include the gastrohepatic ligament and femoral nerve sheath. We detail the salient imaging characteristics, including the T2 'triple signal' pattern which is believed to be highly specific for this particular sarcoma and in many cases predicts a poor outcome. Other poor prognostic factors include haemorrhage, lack of calcification and tumour size >10 cm. A broad range of radiological appearances are described, and in some cases related to anatomical position and size, however the presence of a soft tissue mass close to a joint in a young patient are suggestive of this diagnosis.

Primary superficial synovial sarcoma: clinical and histopathological characteristics in eight cases with molecular confirmation

BACKGROUND AND AIMS

Synovial sarcoma (SS) is a spindled cell sarcoma demonstrating varying degrees of epithelial differentiation and characterized by a pathognomonic t(X;18) translocation. SS most frequently involves deep soft tissue of the extremities in young adults. Superficial SS involving dermis and/or subcutaneous tissue is exceedingly rare.

METHODS AND RESULTS

We identified eight cases of primary superficial synovial sarcomas across three tertiary institutions. All cases were confined to the dermis/subcutis based on imaging or gross and microscopic examination. The average patient age was 36 years (range 14-50). The average tumor size was 2.4 cm (range 0.9-3.9 cm) and lesions showed classic monophasic (n = 4) or biphasic (n = 4) morphology. All tumors expressed keratin AE1/AE3 and/or epithelial membrane antigen (EMA), but were negative for CD34. The diagnosis for each case was confirmed by molecular detection of t(X;18). Six of the eight cases were treated with curative excision while the other two received additional radiotherapy. Follow-up was available for six patients (mean 68 months, range 2-108 months) and no patient experienced recurrence or metastatic disease.

CONCLUSIONS

We present the largest series to date of primary superficial SS with molecular confirmation for all cases. SS should be considered when evaluating a cutaneous monomorphic spindle cell neoplasm.

Primary intramucosal synovial sarcoma of the sigmoid colon in a patient with a germline mutation in the MSH2 gene: A case report

Synovial sarcoma is a high-grade soft tissue sarcoma that occurs primarily in the deep soft tissue of extremities, and primary colorectal synovial sarcoma is extremely rare. In this report, we present a synovial sarcoma mostly located within the mucosa of the sigmoid colon. The patient was a man in his forties with a germline deletion in the MSH2 gene. He had experienced undifferentiated pleomorphic sarcoma of the left forearm 7 years before and adenocarcinoma of the transverse colon 6 years before, both of which were successfully treated and exhibited no recurrence to date. A surveillance colonoscopy for Lynch syndrome revealed the tumor which had a submucosal tumor-like appearance with central erosion and endoscopic resection was performed. Histologically, it was composed of monotonous proliferation of spindle cells arranged in cellular fascicles; these findings were compatible with monophasic fibrous synovial sarcoma. In the tumor cells, the presence of the SS18-SSX1 fusion gene was confirmed. Protein expression of mismatch repair genes was intact in the tumor cells, indicating the association between microsatellite instability and synovial sarcoma was weak. The present case highlights a rare primary site of synovial sarcoma in a patient with Lynch syndrome.

Calcifying synovial sarcoma of the tongue with SS18 rearrangement: a rare variant in a rare location

Synovial sarcoma is a soft tissue malignancy harboring t(X;18) resulting in fusion of two genes SS8 (at 18q11) and SSX (1, 2 or 4 at Xp11) forming the gene fusion product SS18-SSX. It affects adults in their 3rd-4th decades, most frequently in the para-articular regions of the extremities. Less than 10% of the cases occur within the head and neck region and of these, 60% occur in the neck and only 10% occur in the oral cavity. We report a synovial sarcoma of the tongue in a 14-year-old female patient with unusual histology. The patient presented with a mass occupying most of the tongue with extension into the floor of mouth and the lingual gingiva of the anterior mandibular teeth. The tumor was composed of a highly cellular proliferation of spindle cells in a herringbone pattern with many small vessels but without glandular structures, and with extensive calcifications throughout the tumor. Tumor cells were positive for epithelial membrane antigen and transducin-like enhancer of split-1, and fluorescence in situ hybridization studies identified SS18 gene rearrangement. The patient was managed with two debulking procedures followed by chemoradiation and is currently alive with disease.

Synovial Sarcoma of the Nerve-Clinical and Pathological Features: Case Series and Systematic Review

BACKGROUND

Synovial sarcoma of the nerve is a rare entity with several cases and case series reported in the literature. Despite an improved understanding of the biology, the clinical course is difficult to predict.

OBJECTIVE

To compile a series of patients with synovial sarcoma of the peripheral nerve (SSPN) and assess clinical and pathological factors and their contribution to survival and recurrence.

METHODS

Cases from 2 institutions collected in patients undergoing surgical intervention for SSPN. Systematic review including PubMed and Scopus databases were searched for related articles published from 1970 to December 2018. Eligibility criteria: (1) case reports or case series reporting on SSPN, (2) clinical course and/or pathological features of the tumor reported, and (3) articles published in English.

RESULTS

From patients treated at our institutions (13) the average follow-up period was 3.2 yr. Tumor recurrence was seen in 4 cases and death in 3. Systematic review of the literature yielded 44 additional cases with an average follow-up period of 3.6 yr. From pooled data, there were 10 recurrences and 7 deaths (20% and 14%, respectively). Adjuvant treatment used in 62.5% of cases. Immunohistochemical markers used in diagnosis varied widely; the most common are the following: Epithelial membrane antigen (EMA), cytokeratin, vimentin, cluster of differentiation (CD34), and transducin-like enhancer of split 1 (TLE1). Statistical analysis illustrated tumor size and use of chemotherapy to be negative predictors of survival. No other factors, clinically or from pathologist review, were correlated with recurrence or survival.

CONCLUSION

By combining cases from our institution with historical data and performing statistical analysis we show correlation between tumor size and death.

PRAME and HLA Class I expression patterns make synovial sarcoma a suitable target for PRAME specific T-cell receptor gene therapy

Synovial sarcoma expresses multiple cancer testis antigens that could potentially be targeted by T-cell receptor (TCR) gene therapy. In this study we investigated whether PRAME-TCR-gene therapy could be an effective treatment for synovial sarcoma by investigating the potential of PRAME-specific T-cells to recognize sarcoma cells and by evaluating the expression patterns of PRAME and HLA class I (HLA-I) in synovial sarcoma tumor samples. All PRAME expressing sarcoma cell lines, including 2 primary synovial sarcoma cell cultures (passage < 3), were efficiently recognized by PRAME-specific T-cells. mRNA FISH demonstrated that PRAME was expressed in all synovial sarcoma samples, mostly in an homogeneous pattern. Immunohistochemistry demonstrated low HLA-I baseline expression in synovial sarcoma, but its expression was elevated in specific areas of the tumors, especially in biphasic components of biphasic synovial sarcoma. In 5/11 biphasic synovial sarcoma patients and in 1/17 monophasic synovial sarcoma patients, elevated HLA-I on tumor cells was correlated with infiltration of T-cells in these specific areas. In conclusion, low-baseline expression of HLA-I in synovial sarcoma is elevated in biphasic areas and in areas with densely infiltrating T-cells, which, in combination with homogeneous and high PRAME expression, makes synovial sarcoma potentially a suitable candidate for PRAME-specific TCR-gene therapy.

Pleural malignant mesothelioma versus pleuropulmonary synovial sarcoma: a clinicopathological study of 22 cases with molecular analysis and survival data

The aim of this study was to carry out a comparative analysis by transducin-like enhancer of split 1 (TLE1) immunohistochemistry and molecular analysis of SYT-SSX, for 16 pleural predominantly sarcomatoid mesotheliomas and six cases of pleuropulmonary synovial sarcoma (five pleural in distribution only, with one case of a predominantly subpleural upper lobe synovial sarcoma), all of which were solely or predominantly monophasic. Our comparison included survival and some clinical data. We consider that the following points emerged from this study.

Synovial Sarcoma With a Predominant Epithelial Component

A case of synovial sarcoma of the lower leg in a 59-year-old woman with a predomi nant epithelial component is reported. Histologically, the tumor showed a well-devel oped epithelial component with a sheet-like and cribriform pattern with a sparsely distributed spindle cell component. Immunohistochemically, the epithelial component was positive for cytokeratins and epithelial membrane antigen, while the spindle cell component was positive for cytokeratins, epithelial membrane antigen, and vimentin. The epithelial component of synovial sarcoma is indistinguishable from carcinoma morphologically and immunohistochemically, therefore the presence of a biphasic pattern, even with a paucity of spindle cell component, is a crucial finding to establish a diagnosis of synovial sarcoma. The recognition and subclassification of this type of synovial sarcoma is important in arriving at a correct prognosis. Int J Surg Pathol 1(4): 261-268, 1994

Primary Synovial Sarcoma of the Lung

We describe a case of primary pulmonary synovial sarcoma. A 19-year-old man presented with low-grade fever, dyspnea, chest pain and left arm numbness. Chest radiographs revealed a large, well-circumscribed left perihilar mass and a small ipsilateral pleural effusion. Chest computed tomography (CT) revealed a large well-defined, heterogeneous lung mass. Magnetic resonance imaging (MRI) demonstrated a mass of heterogeneous signal intensity on T1-weighted and proton density images, and high signal intensity on short tau inversion recovery (STIR) images. Whole-body bone scintigraphy showed no evidence of skeletal involvement. Abdominal and pelvic CT showed no intra-abominal or pelvic metastases. A CT-guided biopsy provided the diagnosis of monophasic synovial sarcoma. Following four cycles of chemotherapy, integrated F-18 fluorodeoxyglucose positron emission tomography-computed tomography (18F FDG PET/CT) was performed, which demonstrated interval decrease in the size of the lesion and no significant metabolic activity. Surgical resection was then undertaken. Microscopically, the lesion was a high-grade spindle cell sarcoma consistent with monophasic synovial sarcoma. A variant X;18 translocation was identified by cytogenetic analysis and confirmed with metaphase in situ hybridization. The imaging and pathological features of this rare lesion are reviewed.

A rare synovial sarcoma of the spine in the thoracic vertebral body

INTRODUCTION

Synovial sarcomas of the spine are very rare, most rare of which was occurring in the thoracic vertebral body. The diagnosis of synovial sarcomas was very difficult. It depends on the radiological examination, immunohistochemical examination and gene examination. The best treatment to them was completely surgical resection with negative margins. Other treatments such as radiation therapy and chemotherapy were just adjuvant. The prognosis of synovial sarcomas was disappointing.

CASE PRESENTATION

A 26-year-old male patient had low back pain. The radiological examination showed bony erosion of the T7 vertebral body and no soft tissue mass around the spine. He underwent T7 resection en bloc and internal fixation with two levels above T7 and two levels below T7. Then histopathological and gene examination revealed high malignant synovial sarcoma. So he was treated by chemotherapy and external beam radiation therapy after surgery.

CONCLUSION

Primary vertebral body synovial sarcoma is very rare and difficult to diagnose and treat.

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.

Use of immunohistochemical staining and electron microscopy to aid in diagnosis of soft tissue sarcomas associated with the fetlock joint in two horses

Soft tissue sarcomas of the equine distal limb associated with joints, sheaths, or bursae have rarely been reported. Accurate diagnosis of these tumors is challenging in both human beings and veterinary species. Immunohistochemical staining and transmission electron microscopy have been used in human beings to reduce misdiagnosis. The current report describes 2 mature horses presenting with lameness and swelling associated with the dorsal aspect of the metacarpo(tarso)phalangeal joint. In both cases, surgical excision was performed with subsequent histological analysis of the masses to determine the tissue of origin. In both cases, immunohistochemical staining and transmission electron microscopy aided the definitive diagnosis of fibrosarcoma associated with the fetlock joints of 2 horses.

Novel pathways and molecular targets for the treatment of sarcoma

Sarcomas collectively represent over 100 different subtypes of bone and soft tissue tumors of mesenchymal origin. The low response rate to cytotoxic chemotherapies has necessitated the need for development of either histologically driven or pathway-specific targeted therapies. As our understanding of the molecular mechanisms driving certain subtypes is rapidly advancing, the number of targeted therapies is also increasing. Recently identified novel druggable targets include the MDM2 amplifications in well-differentiated and dedifferentiated liposarcomas, the new translocation NAB2:STAT6 of solitary fibrous tumors, the angiopoeitin-TIE2 pathway in angiosarcoma, the suppression of Mcl1 in X:18/synovial sarcomas, the mTOR pathway in malignant peripheral nerve sheath tumors, CDK4 in alveolar rhabdomyosarcoma, cMET regulation in alveolar soft parts sarcoma, the metabolic abnormalities in wild-type/SHD GIST, and the lack of argininosuccinate synthetase 1 expression seen in most sarcomas. It is through a fundamental understanding of sarcoma biology that clinical trials based on molecular targets can be developed.

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.

Malignant small round cell tumors

Malignant small round cell tumors are characterised by small, round, relatively undifferentiated cells. They generally include Ewing's sarcoma, peripheral neuroectodermal tumor, rhabdomyosarcoma, synovial sarcoma, non-Hodgkin's lymphoma, retinoblastoma, neuroblastoma, hepatoblastoma, and nephroblastoma or Wilms’ tumor. Other differential diagnoses of small round cell tumors include small cell osteogenic sarcoma, undifferentiated hepatoblastoma, granulocytic sarcoma, and intraabdominal desmoplastic small round cell tumor. Differential diagnosis of small round cell tumors is particularly difficult due to their undifferentiated or primitive character. Tumors that show good differentiation are generally easy to diagnose, but when a tumor is poorly differentiated, identification of the diagnostic, morphological features is difficult and therefore, no definitive diagnosis may be possible. As seen in several study reports, fine needle aspiration cytology (FNAC) has become an important modality of diagnosis for these tumors. The technique yields adequate numbers of dissociated, viable cells, making it ideally suitable for ancillary techniques. Typically, a multimodal approach is employed and the principal ancillary techniques that have been found to be useful in classification are immunohistochemistry and immunophenotyping by flow cytometry, reverse transcriptase polymerase chain reaction (RT-PCR), fluorescence in situ hybridization (FISH), and electron microscopy. However, the recent characterization of chromosomal breakpoints and the corresponding genes involved in malignant small round cell tumors means that it is possible to use molecular genetic approaches for detection.

Synovial Sarcoma of the Tongue Confirmed by Molecular Detection of the SYT-SSX2 Fusion Gene Transcript

Involvement of the tongue by a synovial sarcoma (SS) is an extremely rare event; there have only been 13 cases previously reported. The authors present herein a case of monophasic SS arising in the tongue in a 32-year-old woman. The neoplasm expressed cytokeratins AE1-3, OSCAR, and EMA as well as Bcl-2 and TLE1. Molecular analysis indicated that the patient tested positive for the SYT/SS2 fusion transcript.

Primary synovial sarcoma of the mediastinum : a case report

Synovial sarcomas commonly occur in the extremities of young adults. A primary occurrence in the mediastinum is very rare with only a few reported cases in the world literature. This paper is about a 42-year-old male who presented with chest pain and dyspnoea on exertion. Imaging showed an anterior mediastinal mass with adhesions to the lung. Pathological examination of the resected mass showed a biphasic neoplasm with a spindle cell component admixed with gland-like elements. The tumour showed positive staining with cytokeratin, epithelial membrane antigen, and Bcl-2 confirming the diagnosis of a biphasic synovial sarcoma. A wide range of neoplasms, both primary and metastatic, occur in the mediastinum, which pose considerable diagnostic difficulties. A synovial sarcoma should always be considered in the differential diagnosis, and immunohistochemistry is an important adjuvant tool in this situation. This paper highlights the importance of recognizing an unusual presentation of this aggressive neoplasm to aid appropriate clinical management.

Gene expression profiling of synovial sarcoma: distinct signature of poorly differentiated type

Poorly differentiated type synovial sarcoma (PDSS) is a variant of synovial sarcoma characterized by predominantly round or short-spindled cell morphology. Although accumulating evidence from clinicopathologic studies suggests a strong association between this variant of synovial sarcoma and poor prognosis, little has been reported on the molecular basis of PDSS. To gain insights into the mechanism(s) that underlie the emergence of PDSS, we analyzed the gene expression profiles of 34 synovial sarcoma clinical samples, including 5 cases of PDSS, using an oligonucleotide microarray. In an unsupervised analysis, the 34 samples fell into 3 groups that correlate closely with histologic subtypes: monophasic, biphasic, and poorly differentiated types. PDSS was characterized by down-regulation of genes associated with neuronal and skeletal development and cell adhesion. Moreover, upregulation of genes on a specific chromosomal locus, 8q21.11, was identified. This locus-specific transcriptional activation in PDSS was confirmed by reverse transcriptase-PCR analysis of 9 additional synovial sarcoma samples. Our results indicate that PDSS tumors constitute a distinct group based on expression profiles.

Synovial sarcoma of the thoracic spine

BACKGROUND CONTEXT

Synovial sarcoma is an uncommon malignant neoplasm occurring chiefly in young adults. It often presents as a solid well-circumscribed soft-tissue mass in the extremities of young adults. Despite its proximity to joints, it has been well established that the tumor cells do not display features of synovial differentiation but instead appear to have a primitive epithelial phenotype. There is no report of a lower thoracic paravertebral synovial sarcoma in an adult male.

PURPOSE

To describe our management in a patient with a synovial sarcoma of the thoracic spine and to review previously published cases.

STUDY DESIGN

Case report.

METHODS

A 60-year-old man presented with a 5-month history of right upper quadrant abdominal pain radiating to his back in a band-like fashion; shortness of breath on exertion; and increasing pain when standing, sitting, or walking. Magnetic resonance imaging (MRI) demonstrated a large right-sided paraspinal mass sitting on the eighth and ninth ribs, pressing on the T9 vertebrae and abutting the T7 and T8 vertebral level exhibiting "Triple Intensity." Plain films demonstrated a right-sided paraspinal mass extending from the T7-T8 level to T10. Bone scintigraphy showed increased uptake on the right thoracic spine at T7-T8 to T10. Computed tomography (CT) imaging revealed a right paraspinal mass with lytic changes in the T9 vertebral bodies. A right-sided thoracotomy was performed, and the patient underwent subsequent radiation therapy. Absence of the tumor was shown by an MRI scan after the operation.

RESULTS

Complete resolution of the patient's complaints was achieved. The diagnosis is supported by plain radiographs, bone scintigraphy, magnetic resonance and CT imaging studies, and histologic and immunohistochemical evidence.

CONCLUSIONS

Synovial sarcomas are rarely present in the paravertebral region of the thoracic spine. A careful radiographic study of the tumor permitted early preliminary diagnosis, confirmed upon histopathologic analysis. Despite lytic changes, removal of a periosteal layer permitted sparing of the vertebral bodies.

A conditional mouse model of synovial sarcoma: insights into a myogenic origin

Synovial sarcoma is an aggressive soft-tissue malignancy marked by a unique t(X;18) translocation leading to expression of a chimeric SYT-SSX fusion protein. We report here a mouse model of synovial sarcoma based on conditional expression of the human SYT-SSX2. Using this model, we have identified myoblasts as a potential source of synovial sarcoma. Remarkably, within the skeletal muscle lineage, while expression of the oncoprotein in immature myoblasts leads to induction of synovial sarcoma with 100% penetrance, its expression in more differentiated cells induces myopathy without tumor induction. We also show that early widespread expression of the fusion protein disrupts normal embryogenesis, causing lethality.

Primary intra-abdominal synovial sarcoma

We report a case of primary intra-abdominal synovial sarcoma of the omentum in a 66-year-old man hospitalized for intermittent abdominal fullness for 1-2 months and tenesmus for 2 weeks. The patient had a palpable mass that was solid, hard and with well-defined thickness within his abdomen. A huge heterogeneous mass lesion over the middle abdomen that started from S2, S3 of the liver to the transverse colon was shown on abdominal computed tomography. The major cell types of the tissue mass were confirmed to be spindle and epithelial cells, which was consistent with biphasic synovial sarcoma according to pathologic and immunohistochemical findings.

Molecular Diagnosis of Sarcomas: Chromosomal Translocations in Sarcomas

Context.—Sarcomas are rare, numerous in type, and often difficult to definitively classify. Work in the last 2 decades has revealed that a significant subset of sarcomas are associated with specific chromosomal translocations producing chimeric (fusion) genes that play a role in the sarcomas' biology and are helpful in their differential diagnosis.

Objective.—To briefly review the sarcomas associated with specific translocations presenting Ewing sarcoma and synovial sarcoma as archetypes and to further explain how cytogenetic and molecular biologic approaches are being used in the diagnosis of sarcomas.

Data Sources.—This work is based on a selected review of the relevant medical and scientific literature and our extensive experience with molecular testing in sarcomas.

Conclusions.—In addition to, and complementing, the traditional diagnostic methods of examination of hematoxylin-eosin stained slides, immunohistochemistry, and sound clinical-pathologic correlation, additional cytogenetic and molecular biologic methods are being increasingly utilized and relied on in sarcoma pathology. These methods include chromosomal karyotyping, fluorescence in-situ hybridization, spectral karyotyping, and polymerase chain reaction– based methods for demonstrating specific chromosomal translocations and fusion genes. Understanding the basis of these methods and their application is critical to better provide accurate and validated specific diagnoses of sarcomas.

Biphasic synovial sarcoma of the abdominal wall

Synovial sarcoma arising in the abdominal wall is a rare tumor. We report a case of a 38-year-old man who complained of abdominal pain. Physical examination revealed a firm mobile mass, 25 cm in diameter, in the left lower abdominal wall. The tumor was first thought to be a sarcoma arising from the omentum or mesentery. During surgery, a large tumor was found attached to the inner surface of the abdominal wall and compressing the gastrointestinal tract. On microscopic examination the tumor corresponded to a biphasic synovial sarcoma immunoreactive for cytokeratins (AE1/AE3, 7 and 19), epithelial membrane antigen and carcinoembryonic antigen in the epithelial tumor cells, for E-cadherin especially in their glandular structure, vimentin, CD99, and CD56 in the spindle cell component and for bcl-2 protein. The tumor recurred at the same site, and clinical course progressed to death 3 months after the initial diagnosis.

SYT-SSX1 and SYT-SSX2 Interfere with Repression of E-Cadherin by Snail and Slug: A Potential Mechanism for Aberrant Mesenchymal to Epithelial Transition in Human Synovial Sarcoma

Synovial sarcoma is a primitive mesenchymal neoplasm characterized in almost all cases by a t(X;18) fusing the SYT transcriptional coactivator gene with either SSX1 or SSX2, with the resulting fusion gene encoding an aberrant transcriptional regulator. A subset of synovial sarcoma, predominantly cases with the SYT-SSX1 fusion, shows foci of morphologic epithelial differentiation in the form of nests of glandular epithelium. The striking spontaneous mesenchymal to epithelial differentiation in this cancer is reminiscent of a developmental switch, but the only clue to its mechanistic basis has been the observation that most cases of synovial sarcoma with glandular epithelial differentiation (GED) contain SYT-SSX1 instead of SYT-SSX2. We report here that SYT-SSX1 and SYT-SSX2 interact preferentially with Snail or Slug, respectively, and prevent these transcriptional repressors from binding to the proximal E-cadherin promoter as shown by coimmunoprecipitation and chromatin immunoprecipitation. Luciferase reporter assays reveal that SYT-SSX1 and SYT-SSX2 can respectively overcome the Snail- or Slug-mediated repression of E-cadherin transcription. This provides a mechanism by which E-cadherin expression, a prerequisite of epithelial differentiation, is aberrantly derepressed in synovial sarcoma and may also explain the association of GED with the SYT-SSX1 fusion because it interferes with Snail, the stronger repressor of the E-cadherin promoter. Thus, our data provide a mechanistic basis for the observed heterogeneity in the acquisition of epithelial characteristics in synovial sarcoma and highlight the potential role of differential interactions with Snail or Slug in modulating this phenotypic transition.

Pleuropulmonary Synovial Sarcoma

Pleuropulmonary synovial sarcoma (PPSS) is increasingly recognized as a subtype of sarcoma because of the recent identification of a distinctive chromosomal translocation specific to synovial sarcoma. Soft-tissue synovial sarcoma is far more common than PPSS and typically develops in para-articular locations of the extremities; affects young and middle-aged adults, with no difference in distribution between the sexes; and has well-documented radiologic manifestations. PPSS may arise in the chest wall, heart, mediastinum, pleura, or lung, and it shares patient demographics and several imaging features with its soft-tissue counterpart. Patients present with a cough, chest pain, or dyspnea. On chest radiographs, PPSS typically appears as a sharply marginated mass with uniform opacity, based either in the pleura or in the lung, and often accompanied by an ipsilateral pleural effusion. Computed tomographic images show a well-circumscribed heterogeneously enhanced lesion without associated involvement of bone and without calcifications (except in the case of a chest wall primary tumor). Magnetic resonance imaging provides superior demonstration of nodular soft tissue and multilocular fluid-filled internal components of PPSS, in addition to peripheral rim enhancement after the intravenous administration of a gadolinium-based contrast material such as gadopentetate dimeglumine. Current treatment consists of surgical resection followed by chemotherapy, radiation therapy, or both.

Synovial sarcoma of the mandible

The term synovial sarcoma was first proposed for the histologically well defined entity by Knox in 1936. The name was proposed due to the fact that at least the cases reported in the early part showed some resemblance of the tumour to normal synovial tissue histologically. Thereafter, tumours have been diagnosed from areas without synovial tissue. The diagnosis of monophasic tumours can be difficult and immunostains appear to be a good diagnostic tool in those cases. The occurrence in the mandible is extremely rare. This is a case of synovial sarcoma arising in the condyle involving most of the ramus. The tumour was diagnosed as synovial sarcoma with predominant spindle cell component by correlation of histopathology with immunostains (cytokeratin, epithelial membrane antigen, actin and desmin). The patient has been treated with surgery and radiotherapy.

The comparative roles of electron microscopy and immunohistochemistry in the diagnosis of soft tissue tumours

Electron microscopy has contributed to the diagnosis of soft tissue tumours for four decades, and immunohistochemistry for two. Because of its relative ease of use and interpretation, the latter technique has become extensively and routinely applied to identify lines of differentiation in benign soft tissue tumours and in sarcomas. The use of electron microscopy has declined but retains a role because few antibodies are wholly specific or fully sensitive, some tumours are polyphenotypic or divergent in differentiation, and others have no specific antigens. Immunohistochemistry is superior in diagnosis of smooth muscle tumours, small round cell tumours, sarcomas with epithelioid morphology, and most synovial sarcomas. Electron microscopy is of particular value for peripheral nerve sheath tumours, marker-negative synovial sarcomas, pleomorphic sarcomas and mesotheliomas. As with all adjunctive techniques, immunohistochemistry and electron microscopy should be used in a complementary fashion according to the nature of the diagnostic problem.

Primary Synovial Sarcomas of the Mediastinum

A series of 15 cases of primary mediastinal neoplasms displaying histopathologic, immunohistochemical, and ultrastructural features of synovial sarcoma is presented. The patients' ages ranged from 3 to 83 years, with a male-to-female ratio of 2:1. Nine cases presented as anterior mediastinal masses with chest pain, shortness of breath, and pleural effusion, and 6 cases were in paravertebral location in the posterior mediastinum and presented with neck or back pain and pleural effusion. The tumors measured from 5 to 20 cm in greatest diameter and showed a tan white, soft to rubbery cut surface with areas of hemorrhage and necrosis and foci of gelatinous material. Four cases showed areas of cystic degeneration. In 7 cases, the tumors were well circumscribed; in 6 cases, the tumors grossly invaded the pleura, pericardium, heart, great vessels, chest wall, rib, and vertebra. Histologically, 5 cases displayed a biphasic growth pattern, with well-formed glandular elements admixed with a monotonous spindle cell population. Ten cases were exclusively composed of a monotonous atypical spindle cell proliferation. Immunohistochemical studies showed focal positivity of the tumor cells for cytokeratin and/or epithelial membrane antigen, and strong positivity for vimentin and bcl-2 in the spindle cells in all cases studied (10 of 10). Eight cases also showed focal positivity for CD99. Electron microscopic examination in 5 cases showed oval to spindle tumor cells with closely apposed cell membranes, abundant cytoplasmic intermediate filaments and rough endoplasmic reticulum, and immature desmosome-type cell junctions. Ten patients were treated by complete surgical excision and two by partial excision followed by radiation therapy. In 4 patients, the tumors were inoperable and treated with radiation therapy only. Clinical follow-up was available in 5 patients and showed local recurrence with metastases to lung, lymph nodes, and epidural space from 1 to 3 years in 4 cases and liver metastases and death due to tumor after 6 month in 1 case. Synovial sarcoma should be considered in the differential diagnosis of biphasic and monophasic spindle cell neoplasms of the mediastinum.

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.

Osteosarcoma with cytokeratin expression: a clinicopathological study of six cases with an emphasis on differential diagnosis from metastatic cancer

AIMS

To clarify the clinicopathological profile of osteosarcomas showing an intensely positive immunoreaction for cytokeratin.

METHODS

Clinicopathological and immunohistochemical features were analysed in 131 patients with non-metastatic, conventional osteosarcoma, treated in Akita University and National Cancer Centre in Tokyo between 1972 and 1999.

RESULTS

Six patients (4.5%; mean age, 32 years; four men, two women) had osteosarcomas showing intense cytokeratin expression. Tumours were located on the long bones of the extremities in five patients and the ilium in one. Osteoid formations were found in biopsied specimens in all cases. Three tumours were classified as osteoblastic osteosarcoma, two as fibroblastic, and one as chondroblastic. In three tumours classified as the osteoblastic subtype, epithelioid features were prominent, and four tumours showed pronounced cellular pleomorphism. In contrast to the expression of cytokeratin, epithelial membrane antigen was negative in all cases. Surgery with a wide excisional margin was performed in six patients. Preoperative and postoperative chemotherapy was given to five of the six patients, but the effects of these agents were negligible. Three of the six patients developed lung metastases, whereas the other three patients have remained well with no evidence of local recurrence or distant metastasis.

CONCLUSIONS

Osteosarcoma with intense immunoreaction for cytokeratin was rare. The clinicopathological features were similar to those of patients with conventional osteosarcoma, except for a higher age, chemotherapy resistance, histological epithelioid features, and pleomorphism. This study indicates that osteoid formation and negative expression of epithelial membrane antigen are key features in the differentiation from metastatic carcinoma.

Splicing isoform of SYT-SSX fusion protein accelerates transcriptional activity and cell proliferation

The human SYT-SSX gene has two splicing isoforms (type N and I), the latter of which contains an additional insertion of 93 bases. In the present study, we found increased transcriptional activity of the SYT-SSX type I protein in luciferase assay. When the SYT-SSX cDNAs were transfected to NIH3T3 cells, the type I transformant grew faster than the type N transformant. Furthermore, we evaluated the isoform ratio of the SYT or SYT-SSX transcripts in various tissues. Our results suggest that the SYT-SSX type I protein plays a critical role in the tumorigenesis of synovial sarcomas through increased transcriptional activity.

Oral synovial sarcoma: a report of 2 cases and a review of the literature

The head and neck region constitutes the second most common site of involvement for synovial sarcoma, accounting for up to 10% of all cases. Intraoral synovial sarcoma is rare; in fact, only 29 cases have been reported. We describe 2 additional cases occurring in the floor of the mouth and the retromolar area. In addition, we have reviewed the clinicopathologic features of the previously reported cases. Our findings indicate that intraoral lesions differ from lesions occurring in other sites only in that intraoral cases show a greater male predilection and a generally painless initial presentation. In the oral cavity, the possible earlier detection, easy accessibility, and small size render these tumors more likely to be amenable to surgical excision, but their biologic behavior remains aggressive, with a poor long-term prognosis. Awareness of the potential for the occurrence of this neoplasm in the oral cavity is important for effective histopathologic diagnosis of intraoral spindle cell malignancies.

Immunohistochemistry in the diagnosis of soft tissue tumours

Immunohistochemistry is particularly important in the field of soft tissue tumours because of their variety and the frequent difficulty of diagnosis. The first part of this paper discusses useful or new antibodies, together with others that are no longer of use. The second part is devoted to the role of immunohistochemistry in the diagnosis of soft tissue tumours: identification of some rare or atypical benign lesions, identification of non-mesenchymal malignant tumours, and classification of sarcomas. The respective roles of immunohistochemistry and molecular biology are underlined.

Calponin and h-caldesmon expression in synovial sarcoma; the use of calponin in diagnosis

AIMS

To assess the frequency of expression and potential diagnostic utility of calponin and caldesmon in synovial sarcomas.

METHODS AND RESULTS

Immunohistochemistry with antibodies to calponin and h-caldesmon was undertaken in paraffin sections from 50 synovial sarcomas (19 biphasic and 31 monophasic, of which one biphasic and eight monophasic tumours had poorly differentiated areas), 10 each of malignant peripheral nerve sheath tumour (MPNST), solitary fibrous tumour (SFT), dermatofibrosarcoma (DFSP), Ewing's sarcoma (ES/PNET), and neuroblastoma, eight alveolar rhabdomyosarcomas, five adult fibrosarcomas and five carcinosarcomas. Nine of 19 biphasic synovial sarcomas were positive for calponin in spindle and glandular areas, nine in spindle cells only, and one in glands only. All monophasic synovial sarcomas and poorly differentiated areas expressed calponin; in monophasic tumours this was focally (29% of cases), moderately (39%), or diffusely (32%) positive and the poorly differentiated areas were usually moderately or diffusely positive. Four synovial sarcomas showed focal reactivity for h-caldesmon. Calponin was found in 4/10 MPNST, 7/10 SFT, 4/10 DFSP, 3/5 fibrosarcomas and the spindle component of the carcinosarcomas. H-caldesmon was weakly positive in 1/10 MPNST, 4/10 SFT, 0/10 DFSP, 0/5 fibrosarcomas and 1/5 carcinosarcomas (glands only). Both markers were negative in the other small round cell tumours.

CONCLUSIONS

Calponin can be used as an additional marker for synovial sarcoma. Its absence argues against the diagnosis. The presence of calponin might be useful in distinguishing poorly differentiated synovial sarcoma from other small round cell tumours. H-caldesmon is not helpful in diagnosis of synovial sarcoma.

Fine-needle aspiration of synovial sarcoma: criteria for diagnosis: retrospective reexamination of 37 cases, including ancillary diagnostics. A Scandinavian Sarcoma Group study

The cytologic criteria of synovial sarcoma in fine-needle aspirates were defined by a retrospective examination of 37 primary tumors. Irrespective of subtype, a typical pattern at low power was found, provided the yield was rich. The typical pattern was a mixture of dispersed cells with the presence of striped nuclei and cell-tight tumor tissue fragments with irregular borders. Often a branching network of vessels was present in the fragments, imitating a true vascular tumor. Except in poorly differentiated synovial sarcomas, the tumor cells were, small to medium in size, with rounded, ovoid, or fusiform bland nuclei with inconspicuous nucleoli. In the biphasic variant, small glandular- or acinar-like structures were present, although not in all cases. In the poorly differentiated type, however, the cellular pleomorphism was marked with the presence of cells with irregular nuclei and rhabdomyoblast-like cells, corresponding to the pleomorphic variant. The Ewing's sarcoma-like and the atypical spindle cell variants of poorly differentiated synovial sarcoma were not diagnosed in the material. An unequivocal diagnosis of sarcoma is possible when the yield is rich. However, ancillary diagnostics are necessary for a correct diagnosis, to avoid important pitfalls, such as other sarcomas with bland tumor cells and vessel-rich tumor fragments, in particular, solitary fibrous tumor and true hemangiopericytoma. Electron microscopic and/or molecular genetic analyses were better diagnostic adjuncts than immunocytochemistry.