[Primary cardiac synovial sarcoma: a clinicopathological analysis of five cases].

Objective: To assess the clinicopathological features, immunophenotype, molecular characteristics and differential diagnosis of primary cardiac synovial sarcoma (PCSS). Methods: Five cases of PCSS were collected at Guangdong Provincial People's Hospital from 2008 to 2023, and their clinicopathological features were summarized. Immunohistochemical staining, fluorescence in-situ hybridization (FISH) and next-generation sequencing (NGS) were performed, and relevant literatures were reviewed. Results: The cases were found in four males and one female, ranging in ages from 16 to 51 years (median 30 years). Two cases were located in the pericardium, two in the right ventricle, and one in the left ventricle. Follow-up data were available in four cases. All the four patients died of disease at 3, 7, 13 and 26 months, respectively, after diagnosis. The tumor maximum diameter ranged from 6.0 to 14.0 cm in (mean 10.0 cm). Microscopically, three cases were monophasic and two cases were biphasic. Immunohistochemically, all cases were immunoreactive for EMA, vimentin, bcl-2 and CD56. The tumor cells were variably positive for pan-cytokeratin, SS18-SSX, SOX2, TLE1, CD99, synaptophysin, calretinin and calponin. FISH showed the presence of SS18 rearrangement in all the cases. NGS detected SS18-SSX gene fusion in three cases (SS18-SSX1 in one and SS18-SSX2 in two). Conclusions: PCSS is an exceedingly rare neoplasm, and should be distinguished from other various malignant epithelial and mesenchymal tumors. The clinical history, histopathological and immunohistochemical features, and molecular findings are all essential to the definitive diagnosis of PCSS.

Synovial sarcoma of the viscera (lung and jejunum): a case report.

We report the case of a woman nearing 70 years old who was admitted to the hospital with a complaint of "epigastric distension for 1 month". Her main signs and symptoms were progressive abdominal distension and occasional abdominal pain. Computed tomography suggested an abdominal mass. She had a surgical history of synovial sarcoma (SS) of the lungs. After admission, she was diagnosed with jejunal SS following a puncture biopsy and laparoscopic surgery. This disease usually occurs in the soft tissues of the limbs, and it is extremely rare for SS to originate in the jejunum. The morphologic heterogeneity of SS overlaps with other tumors and makes the diagnosis particularly difficult. Imaging studies usually lack specificity; however, measuring multiple immunohistochemical markers can greatly assist in the diagnosis and differential diagnosis of SS. This case not only enriches our understanding of SS and describes a rare site of origin, but also emphasizes the importance and challenges of achieving an accurate diagnosis. Immunohistochemical and molecular biological testing have important roles in the definitive diagnosis, highlighting the need for precise and innovative diagnostic and therapeutic approaches in SS.

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.

[Two Cases of Retroperitoneal Synovial Sarcoma].

We experienced two cases of renal primary synovial sarcoma. Case 1: A 29-year-old man underwent laparoscopic radical nephrectomy and was originally diagnosed with renal cell carcinoma. Case 2: A 25-year-old man was treated by open radical nephrectomy since radiographical findings indicated tumor invasion to the ureter causing hydronephrosis. Both cases were pathologically diagnosed as renal synovial sarcomas, and were followed using computed tomography. Recurrence was observed within a year in both cases.

Biphasic synovial sarcoma with epithelial predominance reminiscent of adenocarcinoma: a diagnostic challenge.

Synovial sarcoma (SS) is a rare tumour of unknown origin with peak incidence between 10 and 35 years. Although it arises in juxta-articular location, SS is a misnomer and has no true relationship with synovium. In this case report, we present an elderly female patient with a long-standing history of thigh mass which was initially misdiagnosed as metastatic adenocarcinoma deposits on fine needle aspiration cytology, and again misdiagnosed as malignant adnexal skin tumour on core needle biopsy and referred for further management. Here, we discuss the challenges faced in the diagnosis of SS on a small biopsy and ways to differentiate it from other morphological mimickers. Therefore, we aim to increase the awareness of soft tissue tumours that microscopically appear like adenocarcinoma, which is a potential diagnostic pitfall. We also highlight the importance of morphological diagnosis and the utility of molecular testing using fluorescence in situ hybridisation, to arrive at the correct diagnosis of SS.

Utility of Immunohistochemistry With Antibodies to SS18-SSX Chimeric Proteins and C-Terminus of SSX Protein for Synovial Sarcoma Differential Diagnosis.

Synovial sarcoma is a relatively common soft tissue tumor characterized by highly specific t(X;18)(p11;q11) translocation resulting in the fusion of SS18 with members of SSX gene family. Typically, detection of SS18 locus rearrangement by fluorescence in situ hybridization or SS18 :: SSX fusion transcripts confirms the diagnosis. More recently, immunohistochemistry (IHC) for SS18-SSX chimeric protein (E9X9V) and C-terminus of SSX (E5A2C) showed high specificity and sensitivity for synovial sarcoma. This study screened a cohort of >1000 soft tissue and melanocytic tumors using IHC and E9X9V and E5A2C antibodies. Three percent (6/212) of synovial sarcomas were either negative for SS18-SSX or had scattered positive tumor cells (n=1). In these cases, targeted RNA next-generation sequencing detected variants of SS18 :: SSX chimeric transcripts. DNA methylation profiles of 2 such tumors matched with synovial sarcoma. A few nonsynovial sarcoma tumors (n=6) revealed either focal SS18-SSX positivity (n=1) or scattered positive tumor cells. However, targeted RNA next-generation sequencing failed to detect SS18 :: SSX transcripts in these cases. The nature of this immunopositivity remains elusive and may require single cell sequencing studies. All synovial sarcomas showed positive SSX IHC. However, a mosaic staining pattern or focal loss of expression was noticed in a few cases. Strong and diffuse SSX immunoreactivity was also seen in epithelioid sclerosing osteosarcoma harboring EWSR1 :: SSX1 fusion, while several sarcomas and melanocytic tumors including cellular blue nevus (5/7, 71%) revealed focal to diffuse, mostly weak to intermediate SSX staining. The SS18-SSX and SSX IHC is a useful tool for synovial sarcoma differential diagnosis, but unusual immunophenotype should trigger molecular genetic testing.

Cardiogenic and obstructive shock: primary laryngeal synovial sarcoma with cardiac metastasis.

A man in his 20s with a history of laryngeal synovial sarcoma presented with dyspnoea. Imaging revealed a large right ventricular (RV) mass, which was resected, and histological analysis indicated synovial sarcoma recurrence. Within 1 month of RV mass resection, the tumour progressed with paratracheal metastasis. The lumen was nearly obliterated, and right ventricular outflow tract (RVOT) obstruction led to rapid deterioration with mixed cardiogenic and obstructive shock. We present a rare case of primary laryngeal synovial sarcoma metastasising to the heart.

Primary pulmonary synovial sarcoma with delayed diagnosis in a 69-year-old man: A case report.

RATIONALE: Primary pulmonary synovial sarcoma is a rare malignant pulmonary tumor accompanied by calcifications in approximately 15% of cases. These calcifications usually have a fine, stippled appearance; coarse shapes have seldom been reported. Moreover, the presence of coarse calcifications often suggests benign tumors, which vastly differ in treatment. We present a rare case of primary pulmonary sarcoma with coarse intratumoral calcifications, the diagnosis of which was delayed because of its radiologic appearance. PATIENT CONCERNS: A computed tomography (CT) scan of a 69-year-old man with right upper quadrant (RUQ) pain revealed an incidental mass at the base of the right lower lobe, the margin of which was not well described with respect to the liver, and intratumoral coarse calcification was noted. Initially, the lesion was believed to be hepatic, and magnetic resonance imaging (MRI) was performed. Based on its imaging features, the mass was thought to be a pulmonary lesion, and a preliminary diagnosis of a benign lesion, such as a hamartoma or granuloma, was made. Four months after the initial CT scan, the patient's RUQ pain had aggravated; however, no change in the mass was observed on follow-up CT. DIAGNOSIS: The final diagnosis was primary pulmonary sarcoma, proven by surgical biopsy. INTERVENTIONS: Wedge resection of the right lower lobe was performed, and the patient received adjuvant chemotherapy. OUTCOMES: The patient's RUQ pain improved, and no recurrence or metastasis has been reported to date. LESSONS: This case describes a rare presentation of a primary pulmonary synovial sarcoma with coarse intratumoral calcifications and the MRI features of the lesion. Intratumoral coarse calcifications often suggest benign lesions, such as hamartomas or post-inflammatory granulomas; however, as malignant lesions cannot be completely excluded, other radiologic and clinical features should be considered carefully. Focal areas of enhancement and eccentric calcification distribution might suggest malignant lesions such as primary pulmonary synovial sarcoma. Furthermore, despite not being used routinely, MRI scans might be helpful because advanced MRI techniques, such as diffusion-weighted imaging, can help distinguish malignant lesions from benign lesions. If the clinical course of a patient suggests malignancy, a more aggressive biopsy strategy should be considered.

Successful reconstruction using a buccal fat pad flap in misdiagnosed buccinators intramuscular synovial sarcoma: A case report.

INTRODUCTION: Synovial sarcoma (SS) is a subtype of soft tissue sarcoma that primarily usually occurs in the lower extremities but rarely arises in the head and neck areas, including the oral cavity. Due to its variable presentation and similarity to benign masses in terms of age at onset, growth rate, and favorable outcomes, SS is often misdiagnosed as a benign tumor. However, it is a malignant tumor. PATIENT CONCERNS: We report the case of intramuscular SS in the oral cavity. Initially, the lesion was clinically suspected as a benign mass but was ultimately confirmed as malignant SS. DIAGNOSIS: Although histopathological examination is the first step in diagnosing SS, molecular testing to confirm the presence of SYT-SSX fusion can provide a definitive diagnosis when the histopathology is inconclusive. In this patient as well, the postoperative pathological report confirmed the diagnosis of biphasic SS, and molecular testing revealed positive SYT/SSX fusion. THERAPEUTICS INTERVENTIONS: Following the recommendation of multidisciplinary care system, a wide excision was performed including the buccinators muscle, and reconstruction was performed using a buccal fat pad flap to prevent cheek depression. OUTCOMES: On the final pathologic report, SS was removed margin-free, and there were no metastatic lymph nodes. No evidence of cheek dimpling was observed, and follow-up neck CT showed no significant changes in the lymph nodes. As a result of observation up to several months after surgery, there were no functional and aesthetic complications. CONCLUSIONS: We report a successful case of intramuscular SS resection, initially misdiagnosed as a benign mass, using a buccal fat pad flap. We also highlight the importance of correctly diagnosing SS, especially in the craniofacial region where it can be mistaken for benign masses.

Indolent Multinodular Synovial Sarcoma of Peripheral Nerves Mimicking Schwannoma: A Case Report and Literature Review.

BACKGROUND/AIM: Most cases of synovial sarcoma (SS) are aggressive and large-sized; only few show indolent behavior, having a small size. Nerves are rare sites of SS occurrence. An atypical case of SS can lead to its misdiagnosis as a benign tumor and delay its treatment. CASE REPORT: Here, we report a case of primary SS of indolent multinodular synovial sarcoma of peripheral nerves. Considering the clinical and imaging findings at the first visit, we suspected a benign tumor and continued careful follow-up. Three years later, marginal resection was performed and SS was suspected. We then performed an additional wide resection using a free flap. Histopathologically, the proximal tumor showed a diffuse proliferation of spindle cells without pleomorphism, whereas the distal tumor showed a similar histology with more hypercellularity. Additional wide-resection specimens showed remnant tumors derived from the peripheral nerve. Immunohistochemistry (IHC) showed positive staining for SS18:SSX and SSX in both tumors and fluorescence in situ hybridization showed positive staining for the SS18 split in both tumors. Finally, SS of the peripheral nerve was diagnosed. Owing to FNCLCC grade 2 tumor and tumor size, adjuvant chemotherapy was not performed. CONCLUSION: In cases of SS or other sarcomas with atypical clinical courses, with imaging findings mimicking benign tumors, we recommend marginal resection along with pathological examination for correct diagnosis.

Primary synovial sarcoma and acinar adenocarcinoma of prostate rarely occur simultaneously: A case report.

RATIONALE: Primary synovial sarcoma of the prostate is an extremely rare mesenchymal malignant soft tissue tumor with unique morphological features. Synovial sarcoma often occurs in the pararticular tissues of limbs in young people, but rarely occurs in prostate. Because it is very rare, it is easily misdiagnosed as benign prostatic hyperplasia or prostate cancer clinically. A case of synchronous acinar adenocarcinoma of the prostate has not been reported. In this article, we report a unique case of primary prostatic synovial sarcoma with acinar adenocarcinoma. PATIENT CONCERNS: A 58-year-old male patient was found to have a prostate mass during physical examination. Prostate ultrasound examination showed an increase in prostate volume of 5.2 × 3.3 × 3.3 cm, mixed echo mass can be seen on the left side of the prostate, with a size of approximately 4.9 × 4.3 cm, left seminal vesicle compressed. DIAGNOSES: Prostatic synovial sarcoma (biphasic type) combined with prostatic acinar adenocarcinoma (Gleason 3 + 3). INTERVENTION: The patient received radical prostatectomy, followed by adjuvant chemotherapy and radiotherapy. OUTCOME: After 2 months of follow-up, at the time of writing this article, the patient received a comprehensive treatment plan of adjuvant chemotherapy and radiotherapy for 2 months, and no recurrence or metastasis was found. LESSONS: Primary prostatic synovial sarcoma (biphasic type) combined with prostatic acinar adenocarcinoma is a very unique and rare case, and effective treatment guidelines are not yet clear, posing new challenges to clinical treatment. Making full use of pathological and imaging examinations, early diagnosis and radical surgery combined with multidisciplinary treatment seem to be still a positive method.

[Oncological outcomes and prognostic factors in surgically treated patients with synovial sarcoma]. / Resultados oncológicos y factores pronósticos en pacientes con sarcoma sinovial tratados quirúrgicamente.

INTRODUCTION: Synovial sarcoma is an unusual tumor with an incidence of 1-3 cases per million. It is more frequent in teenagers and young adults under 30. It develops anywhere, but the extremities are the most frequent place of appearance (80% extremities, 20% other locations: 8% trunk, 7% retroperitoneal/abdominal, 5% head and neck). Oncological results are different depending on the study. Survival rate free of local recurrence, survival rate free of events and global survival rate vary upon published studies. The same happens with the disease's prognostic factors. METHODS: The objective was to analyze a group of 43 patients with diagnosis of synovial sarcoma of the extremities treated surgically and determine (1) global survival rate, (2) survival rate free of events, (3) local recurrence rate and (4) oncological risk factors. RESULTS: The global survival rate at 2 years was 90% (IC95%: 76 - 96%) and 67% (IC95%: 49-80%) at 5 years. The survival rate free of events at 2 years was 68% (IC95% 51-80%) and 48% (IC95% 32-52%) at 5 years. The recurrence rate at 2 years was 9% (IC95% 3-25%) and 25% (IC95% 13-46%) at 5 years. The histological grade and metastatic presence were bad prognostic factors. DISCUSSION: We can conclude that our oncological results are in line with those published in previous series and that there were two factors associated with poor prognosis.

Introducción: El sarcoma sinovial es un tumor raro (incidencia de 1-3 casos por millón). Es más frecuente en adolescentes y adultos menores de 30 años. Se desarrolla en cualquier parte del cuerpo, siendo, las extremidades el lugar más frecuente de aparición (80% extremidades y 20% otras localizaciones: 8% tronco, retroperitoneal/ abdominal 7%, cabeza y cuello 5%). Los resultados oncológicos de los pacientes con sarcoma sinovial son disímiles. La tasa de supervivencia libre de recurrencia local, la supervivencia libre de eventos y la supervivencia global varían entre las series publicadas. Lo mismo sucede con los factores pronósticos de la enfermedad. Métodos: El objetivo fue analizar un grupo de 43 pacientes con diagnóstico de sarcoma sinovial de las extremidades tratados quirúrgicamente, y determinar (1) tasa de supervivencia global, (2) tasa de supervivencia libre de eventos, (3) tasa de recurrencia local y (4) factores de riesgo oncológicos. Resultados: La supervivencia global a los 2 años fue 90% (IC95%: 76-96%), y 67% (IC95%: 49-80%) a los 5 años. La supervivencia libre de eventos a los 2 años fue 68% (IC95% 51-80%) y a los 5 años 48% (IC95% 32-52%). El riesgo de recurrencia local a 2 años fue 9% (IC95% 3-25%) y a los 5 años 25% (IC95% 13-46%). Los factores de mal pronóstico oncológico fueron el grado histológico y la presencia de metástasis. Discusión: Podemos concluir que nuestros resultados oncológicos se asemejan a las series publicadas y que en nuestra serie hubo dos factores de mal pronóstico.

Synovial sarcoma with ossification and calcification with SS18 immunochemical expression and rearrangement by fluorescent in situ hybridization.

Synovial sarcoma is a soft tissue tumor of uncertain origin. Generally, it is a monophasic spindle cell neoplasm that can have glandular-like structures. Ossification and presence of calcification is a rare phenomenon with only a few reported cases. We present the case of a young male with a synovial sarcoma of the right foot. Histology revealed prominent deposits of tumoral osteoid and coarse calcifications. The diagnosis was confirmed by the expression of SS18 by immunohistochemistry and the demonstration of the rearrangement of the SS18 gene by fluorescent in situ hybridization. We reviewed the literature for synovial sarcoma with prominent ossification or calcification, and to the best of our knowledge, this is the first case with expression of SS18 by immunohistochemistry. The main differential diagnoses are osteosarcoma (both primary of bone and extraosseous) and sclerosing epithelioid fibrosarcoma.

Synovial sarcoma of female urethra: a case report and review of the literature.

Synovial sarcoma (SS) is a rare malignant soft tissue sarcoma that originates from primitive mesenchymal cells with epithelial differentiation potential. It is most commonly found in the limbs and trunk. In the urinary system, it is mostly found in the kidneys. However, synovial sarcomas originating from the external urethra are extremely rare. Only one case of synovial sarcoma arising from the vulvar urethral orifice has been reported previously, and we report a second case of synovial sarcoma of the urethral orifice. In addition, a total of 16 vulvar synovial sarcomas were identified and the literature are analyzed in this report reviews from 1966 to the present.

[Poorly differentiated synovial sarcoma of the chest wall with rhabdoid features]. / Sarcoma sinovial pobremente diferenciado de pared del tórax con características rabdoides.

We report a rare case of a poorly differentiated synovial sarcoma (SS) with rhabdoid features. A 33-year-old woman was referred to our hospital with a chest wall tumor. MRI revealed a diffuse mass that invaded the pleura and extended into the esophagus, aorta, diaphragm and pancreas. Histopathological examination of the neoplasm showed it to be composed of sheets of small/medium cells with rhabdoid morphology, consisting of round, eccentrically localized nuclei, conspicuous nucleoli, and eosinophilic cytoplasm. Immunohistochemical studies demonstrated the tumor cells to be positive for TLE1, Bcl-2, EMA, CAM5.2, CD138 and CD56 and negative for desmin, smooth muscle actin or S100 protein. Fluorescent in-situ hybridization technique, performed on the paraffin section, showed SS18 gene rearrangement in the nuclei of the tumor cells. Poorly differentiated SS with "rhabdoid" features was diagnosed. This is only the 8th case of a SS with "rhabdoid" features reported to date.

SS18-SSX Antibody: A Useful Tool to Save Time and Reduce Costs in Synovial Sarcoma Diagnosis. Proposal of a Novel Diagnostic Algorithm.

Synovial sarcoma is a rare malignant mesenchymal neoplasm mostly affecting young adults, characterized by a specific translocation which results in the fusion of the SS18 gene on chromosome 18 with one of the three highly homologous SSX genes on chromosome X. Its morphological diagnosis, especially in monophasic or poorly differentiated variants, can be challenging because histological features often overlap with other malignant mesenchymal tumors. Until recently, the differential diagnosis mostly relied on the use of cytogenetic or molecular analyses to detect the specific t(X;18)(p11;q11) translocation, thus virtually restricting its correct identification to referral centers with a high histological and molecular pathology workflow. The recently commercialized highly sensitive and fusion-specific SS18-SSX antibody has significantly improved the approach to these tumors, representing a relatively cheap and easy to access tool for synovial sarcoma diagnosis. Through a retrospective analysis of 79 synovial sarcomas and histological mimickers, this study confirms the usefulness of the SS18-SSX antibody in the diagnosis of synovial sarcoma, particularly focusing on its application in the pathological response evaluation after neoadjuvant treatment as well as its time- and cost-saving advantages. Finally, we here propose a new diagnostic algorithm to apply into the routine practice.

Neumotórax espontáneo persistente como manifestación primaria de sarcoma sinovial pleuropulmonar primario: a propósito de un caso / Persistent spontaneous pneumothorax as a primary manifestation of primary synovial sarcoma of the lung: a case report

El sarcoma sinovial pleuropulmonar (SSPP) es un tumor primario de pulmón, maligno, infrecuente en pediatría (prevalencia 0,1-0,5 %) que afecta predominantemente a adolescentes y adultos jóvenes. Se ha descrito una sobrevida global cercana al 30 % a los 5 años. Se reporta el caso de un paciente de 12 años de edad, previamente sano, que presentó tos, dolor torácico y disnea de comienzo súbito, como manifestación inicial de neumotórax izquierdo, el que persistió a los 4 días y requirió resección quirúrgica de lesión bullosa pulmonar. Se realizó diagnóstico histológico de sarcoma sinovial pleuropulmonar confirmado por estudio molecular, que evidenció la translocación cromosómica entre el cromosoma X y el 18: t(X;18) (p11.2;q11.2) de la pieza quirúrgica extirpada. Ante pacientes con neumotórax persistente o recidivante, es importante descartar causas secundarias, entre ellas, sarcoma sinovial pleuropulmonar. Su ominoso pronóstico determina la necesidad de arribar a un diagnóstico temprano e implementar un tratamiento agresivo

Pleuropulmonary synovial sarcoma (PPSS) is a primary malignancy of the lung, uncommon in pediatrics (prevalence: 0.1­0.5%) that predominantly affects adolescents and young adults. Overall survival has been reported to be close to 30% at 5 years. Here we report the case of a previously healthy 12-year-old male patient who presented with cough, chest pain, and dyspnea of sudden onset as initial manifestation of left pneumothorax, which persisted after 4 days and required surgical resection of pulmonary bullous lesion. A histological diagnosis of pleuropulmonary synovial sarcoma was made and confirmed by molecular study, which showed chromosomal translocation between chromosomes X and 18: t(X;18) (p11.2;q11.2) in the surgical specimen removed. In patients with persistent or recurrent pneumothorax, it is important to rule out secondary causes, including pleuropulmonary synovial sarcoma. Such poor prognosis determines the need for early diagnosis and aggressive treatment.

Synovial sarcoma: cytopathology of 51 cases highlighting the application of ancillary molecular testing.

INTRODUCTION: Among sarcomas, synovial sarcoma (SS) is defined by its unique SS18 cytogenetic translocation. Fine needle aspiration (FNA) biopsy is in a key position to exploit this uniqueness for diagnostic purposes. MATERIALS AND METHODS: Our cytopathology files were searched for examples of SS with histopathologic verification. FNA biopsy, imprint smears, and core needle biopsy (CNB) were performed using standard techniques. RESULTS: Fifty-one cases from 49 patients (male/female ratio, 1:1; age range, 12-79 years; mean age, 40 years) met the inclusion criteria. Of the 51 cases, 44 (86%) were FNAs, 6 were cytology imprints, and 1 was pleural fluid. Eleven aspirates had concurrent CNB. All cases had tissue confirmation. The biopsy sites included extremities (n = 24; 47%), trunk (n = 12; 24%), lung (n = 8; 16%), head or neck (n = 6; 12%), and pleural fluid (n = 1; 2%). The aspirates were from primary (n = 36; 71%), metastatic (n = 12; 24%), and recurrent (n = 3; 5%) neoplasms. The cytologic diagnoses were SS (69%), suspicious for SS (12%), malignancy (10%), spindle cell neoplasm (4%), and malignancy other than SS (6%). In general, smears and imprints contained dense cell aggregates and single cells composed of a monotonous population having fusiform, rounded, or ovoid banal nuclei and scant cytoplasm. Poorly differentiated SS showed both large epithelioid cell and small cell cytomorphology. When performed, SS18 immunohistochemical and genetic testing was positive in all 19 FNA and 3 CNB cases. CONCLUSIONS: When coupled with appropriate ancillary testing, FNA biopsy allows for a specific, accurate diagnosis of SS in most cases.

Novel characteristics for immunophenotype, FISH pattern and molecular cytogenetics in synovial sarcoma.

As a rare and highly aggressive soft tissue sarcoma, the new immunophenotype, atypical FISH pattern and relevant molecular cytogenetics of synovial sarcoma (SS) remain less known, although it is characteristically represented by a pathognomonic chromosomal translocation t (X; 18) (p11.2; q11.2). Methodologically, the morphology was retrospectively analysed by using H&E staining, and immunohistochemical features were investigated by using markers that have been recently applied in other soft tissue tumors. Moreover, FISH signals for SS18 and EWSR-1 break-apart probes were examined. Finally, cytogenetic characteristics were analysed via RT-PCR and Sanger sequencing. Consequently, nine out of thirteen cases that were histologically highly suspected as SS were finally identified as SS via molecular analysis. Histologically, nine SS cases were divided into monophasic fibrous SS (4/9), biphasic SS (4/9) and poorly differentiated SS (1/9). Immunohistochemically, SOX-2 immunostaining was positive in eight cases (8/9) and PAX-7 immunostaining was diffusely positive in the epithelial component of biphasic SS (4/4). Nine cases showed negative immunostaining for NKX3.1 and reduced or absent immunostaining for INI-1. Eight cases showed typically positive FISH signalling for the SS18 break-apart probe, whereas one case exhibited an atypical FISH pattern (complete loss of green signalling, case 2). Furthermore, the SS18-SSX1 and SS18-SSX2 fusion genes were identified in seven cases and two cases, respectively. The fusion site in 8 out of 9 cases was common in the literature, whereas the fusion site in case 2 was involved in exon 10 codon 404 in SS18 and exon 7 codon 119 in SSX1 (which has not been previously reported), which notably corresponded to the complete loss of green signalling in the FISH pattern. Additionally, FISH analysis of the EWSR-1 gene in nine SS cases demonstrated aberrant signalling in three cases that were recognized as a monoallelic loss of EWSR-1 (1/9), an amplification of EWSR-1 (1/9) and a translocation of EWSR-1 (1/9). In conclusion, SS18-SSX fusion gene sequencing is obligatory for a precise diagnosis of SS when dealing with a confusing immunophenotype and atypical or aberrant FISH signalling for SS18 and EWSR-1 detection.