[Imaging characteristics and diagnosis of primary middle mediastinal tumors].

Objectives: To investigate the proportion of different histological types and CT enhanced imaging features of primary middle mediastinal lesions in order to improve the understanding of these tumors and the accuracy of preoperative diagnosis. Methods: Retrospective analysis was conducted on 84 patients with primary middle mediastinal lesions and clear histological classifications diagnosed and treated at the Cancer Hospital, Chinese Academy of Medical Sciences from January 2012 to December 2022. Clinical, imaging, and pathological data were collected and classified according to tumor histological classifications. CT imaging manifestations such as tumor location, size, morphology, edge, boundary, internal components, enhancement characteristics, and surrounding tissue invasion were evaluated and recorded. Results: The histological types of the primary middle mediastinal lesions from the 84 patients included mesenchymal tumors, anterior intestinal cysts, giant lymph node hyperplasia, substernal goiter, neuroendocrine carcinoma, lymphohematopoietic system tumors, and mesothelioma, accounting for 28.6%, 27.4%, 14.3%, 3.6%, 11.9%, 9.5%, and 4.8%, respectively. Mesenchymal tumors included peripheral nerve sheath tumors, vascular tumors, adipogenic tumors, solitary fibrous tumors, and synovial sarcoma, accounting for 54.2%, 20.8%, 12.5%, 8.3%, and 4.2%, respectively. The above tumors had diverse imaging manifestations and specific imaging features. Mature fat were found in 3 cases of liposarcoma; Calcification was observed in 2 cases of thyroid nodules and 7 cases of giant lymph node hyperplasia; Enhanced scanning showed significant enhancement in 2 cases of solitary fibrous tumors, 3 cases of thyroid nodules, and 11 cases of giant lymph node hyperplasia; Mediastinal large lymph nodes was observed in 6 cases of lymphoma and 3 cases of mesothelioma; High invasiveness was observed in 4 cases of mesothelioma and 9 cases of neuroendocrine carcinoma. Conclusion: Mediastinal tumors have low incidence rate and rich histological types, and their imaging manifestations are diverse. Preoperative differential diagnosis can be made according to their specific imaging characteristics.

A giant synovial sarcoma of the left lung.

Primary pulmonary synovial sarcoma is an extremely rare and aggressive neoplasm that primarily affects young people and has a poor prognosis. Establishing this diagnosis requires the exclusion of a wide number of other neoplasms with multimodal clinical, imaging, histological, immunohistochemical, and cytogenetic assessment. We present a case of synovial sarcoma of the left lung in a 44-year-old man, diagnosed immunohistochemically after left lower lobectomy with atypical resection of the 5th segment. Imaging, diagnostic workup, histological and immunohistochemical characteristics, surgical treatment, and prognosis are discussed.

[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.

Complete resection of a giant intrapericardial cardiac synovial sarcoma.

Synovial sarcoma of the heart is a rare tumor. Herein we would like to report a case of giant intrapericardial cardiac synovial sarcoma that originated from the right ventricle and grew outward near the diaphragm. After making adequate preoperative preparation, we performed the surgery as quickly as possible and resected the tumor completely. Based on the identification of the translocation on chromosome 18 rearrangement, the tumor can be diagnosed as a primary cardiac synovial sarcoma. Through this study, we aim to afford more information about cardiac synovial sarcomas as well as a reference for similar cases.

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.

Recurrent Synovial Sarcoma with Breast and Pulmonary Nodule: A Case Report.

Synovial sarcoma is a mesenchymal tumour with partial epithelial differentiation. About 85-90% of SS occur in the extremities. We present a case of a 44-year-old woman diagnosed with recurrent synovial sarcoma with breast and pulmonary nodules. The primary treatment for synovial sarcoma is wide surgical excision, while chemotherapy is reserved for metastatic cases. In the first-line metastatic setting, combination treatment with adriamycin and ifosfamide is administered. Despite the unfavourable prognosis, the patient's extended survival is fortunately not the typical outcome. Keywords: case reports; chemotherapy; immunohistochemistry; synovial sarcoma.

[Renal synovialosarcoma: What about pyelic cytology to make a diagnosis?] / Synovialosarcome primitif du rein : si tout était déjà dans les urines pyéliques ?

Synovialosarcoma is a malignant mesenchymal tumor of young adults that occurs in the deep soft tissues, particularly around large joints. When it occurs in more unusual sites, it could present a significant diagnostic challenge. In this case, a 19-year-old girl was treated for a pyloric mass. A pyelic urine cytology performed simultaneously with a pyloric biopsy proved to be a significant element of orientation and perfectly concordant with the histopathological aspect of the pyelic mass after nephrectomy. We report here the first case of renal synovialosarcoma documented in pyelic urine.

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.

Small gastric synovial sarcoma diagnosed and treatment by laparoscopic-endoscopic cooperative surgery: a case report.

We report a case of small gastric synovial sarcoma (SS) finally diagnosed after laparoscopic-endoscopic cooperative surgery (LECS). A 50 year-old male underwent medical examination for a chief complaint of epigastric pain. Endoscopic examination showed a 20 mm submucosal tumor (SMT) located in the anterior wall which extended to the lesser curvature of the middle stomach. The biopsy tissue did not yield a definitive diagnosis. During 6 months of follow-up for this lesion suspected to be an inflammatory tumor, neither the shape nor the size of the tumor changed. We performed LECS for both diagnosis and treatment. Histologically, the tumor was composed of fascicles of spindle cells. Immunohistochemically, the tumor cells were focally positive for epithelial membrane antigen, cytokeratin (AE1/AE3) and S100 protein, while being negative for desmin, α-smooth muscle actin, CD34, c-kit and DOG1. The expression of INI1 was reduced. Fluorescence in situ hybridization (FISH) detected SS18 rearrangement. The SMT was diagnosed as primary SS. A SMT measuring < 20 mm might be malignant potential tumor such as SS even if there are no typical malignant findings by endoscopy. Surgical resection should be considered for SMT measuring < 20 mm with atypical findings even in the absence of definitive high-risk features.

Synovial Sarcoma of the Gastrointestinal Tract.

We report the clinicopathologic and immunohistochemical features of 18 cases of confirmed primary synovial sarcoma of the gastrointestinal tract. The neoplasms arose in 10 women and 8 men ranging in age from 23 to 81 years (mean: 50; median: 57.5 years). The tumors for which size was known ranged from 1.8 to 15.0 cm (mean: 5.2; median: 5.1 cm). Microscopically, 14 synovial sarcomas were of the monophasic type, 2 were biphasic, and 2 were poorly differentiated. Immunohistochemical analysis of 4 cases showed strong, diffuse staining for SS18::SSX (4/4 cases). Pancytokeratin and EMA immunohistochemistry were performed on 13 and 9 tumors, respectively, and each showed patchy-to-diffuse staining. By reverse-transcription PCR, 3 cases were positive for the SS18::SSX1, and 2 cases were positive for the SS18::SSX2 gene fusion. Six cases contained an SS18 gene rearrangement by fluorescence in situ hybridization, and next-generation sequencing identified an SS18::SSX2 gene fusion in one case. Clinical follow-up information was available for 9 patients (4 months to 4.6 years; mean, 2.8 y; median: 29 months), and one patient had a recent diagnosis. Three patients died of disease within 41 to 72 months (mean, 56 months) of their diagnosis. Five patients were alive without evidence of disease 4 to 52 months (mean, 17.6 months) after surgery; of whom 1 of the patients received additional chemotherapy treatment after surgery because of recurrence of the disease. A single patient was alive with intraabdominal recurrence 13 months after surgery. We conclude that synovial sarcoma of the gastrointestinal tract is an aggressive tumor, similar to its soft tissue counterpart, with adverse patient outcomes. It is important to distinguish it from morphologically similar gastrointestinal tract lesions that may have different treatment regimens and prognoses.

Diagnostic Utility of GATA3 and ISL1 in Differentiating Neuroblastoma From Other Pediatric Malignant Small Round Blue Cell Tumors.

Accurate diagnosis of neuroblastoma may be challenging, especially with limited or inadequate specimen and at the metastatic sites due to overlapping imaging, histopathologic, and immunohistochemical (immunohistochemistry [IHC]; infidelity among various lineage-associated transcription factors eg FLI1, transducin-like enhancer 1, etc) features. GATA3 and ISL1 have recently been described as markers of neuroblastic differentiation. This study aims at determining the diagnostic utility of GATA3 and ISL1 in differentiating neuroblastoma from other pediatric malignant small round blue cell tumors.We evaluated GATA3 and ISL1 expression in 74 pediatric small round blue cell tumors that included 23 NMYC-amplified neuroblastomas, 11 EWSR1-rearranged round cell sarcomas, 7 SYT::SSX1-rearranged synovial sarcomas, 5 embryonal rhabdomyosarcomas, 10 Wilms tumors (nephroblastomas), 7 lymphoblastic lymphoma, 7 medulloblastoma, and 4 desmoplastic small round cell tumor.All 23 neuroblastomas (moderate to strong staining in >50% of the tumor cells), 5 T-lymphoblastic lymphomas (moderate to strong staining in 40%-90% of the tumor cells), and 2 desmoplastic small round cell tumors (weak to moderate staining in 20%-30% of the tumor cells) expressed GATA3, while other tumors were negative. ISL1 immunoreactivity was observed in 22 (96%) neuroblastomas (strong staining in in >50% of the tumor cells, n = 17; moderate to strong staining in 26%-50% of the tumor cells, n = 5), 3 embryonal rhabdomyosarcoma (moderate to strong staining in 30%-85% of the tumor cells), 1 synovial sarcoma (weak staining in 20% of the tumor cells), and 7 medulloblastoma (strong staining in 60%-90% of the tumor cells). Other tumors were negative. Overall, GATA3 showed 86% specificity, 100% sensitivity, and 90% accuracy for neuroblastoma, with a positive predictive value (PPV) and negative predictive value (NPV) of 77% and 100%, respectively. ISLI showed 72% specificity, 96% sensitivity, and 81% accuracy for neuroblastoma, with a PPV and NPV of 67% and 97%, respectively. After the exclusion of T-lymphoblastic lymphoma and desmoplastic small round cell tumors, GATA3 had 100% specificity, sensitivity, accuracy, and PPV and NPV for neuroblastoma. Similarly, in pediatric small round blue cell tumors, ISL1 had 100% specificity, sensitivity, accuracy, PPV, and NPV for neuroblastoma, after embryonal rhabdomyosarcoma, synovial sarcoma, and medulloblastoma were excluded. CONCLUSIONS: GATA3 and ISL1 may be valuable in the diagnostic work-up of neuroblastoma and may reliably be used to support the neuroblastic lineage of pediatric small round blue cell tumors. Furthermore, dual positivity helps in challenging scenarios, when there is equivocal imaging, overlapping IHC features, limited specimen, and the lack of facility for a molecular work up.

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.

Team Approach: Extremity Soft Tissue Sarcoma.

¼ Synovial sarcoma is a soft tissue sarcoma that most commonly presents in the extremity in a periarticular location.¼ As the history and physical examination of patients with synovial sarcoma can overlap considerably with those of patients with non-oncologic orthopedic conditions, it is important that orthopedic surgeons maintain a high level of suspicion when caring for patients with extremity masses.¼ Soft tissue sarcomas are best treated using a team approach. Early recognition and referral to a multidisciplinary sarcoma team are crucial to ensure the best clinical outcome for the patient.

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.

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.

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.

[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.

[Primary synovial sarcoma of lung: a clinicopathological analysis of 12 cases].

Objective: To investigate the clinicopathological features, immunophenotype, molecular features and differential diagnosis of primary synovial sarcoma of the lung (PSSL). Methods: Twelve cases of PSSL were collected at Henan Provincial People's Hospital, during May 2010 and April 2021, and their clinicopathological parameters were summarized. SS18-SSX, H3K27Me3, and SOX2 were added to the original immunomarkers to evaluate their diagnostic value for PSSL. Results: The age of 12 patients when diagnosed ranged from 32 to 75 years (mean of 50 years). There were 7 males and 5 females, 2 left lung cases and 10 right lung cases. Of the 6 patients who underwent surgical resection, five cases were confined to lung tissue (T1), one case had mediastinal invasion (T3), two cases had regional lymph node metastasis (N1), and none had distal metastasis. Microscopically, 11 cases showed monophasic spindle cell type and one case showed biphasic type composed of mainly epithelial cells consisting of cuboidal to columnar cells with glandular and cribriform structures. It was difficult to make the diagnosis by using the biopsy specimens. Immunohistochemistry (IHC) showed CKpan expression in 8 of 12 cases; EMA expression in 11 of 12 case; TLE1 expression in 8 of 12 cases; S-100 protein expression in two of 12 cases; various expression of bcl-2 and vimentin in 12 cases, but no expression of SOX10 and CD34 in all the cases. The Ki-67 index was 15%-30%. The expression of SS18-SSX fusion antibody was diffusely and strongly positive in all 12 cases. SOX2 was partially or diffusely expressed in 8 of 12 cases, with strong expression in the epithelial component. H3K27Me3 was absent in 3 of 12 cases. SS18 gene translocation was confirmed by fluorescence in situ hybridization (FISH) test in all 12 samples. Six cases underwent surgery and postoperative chemotherapy, while the other six cases had chemotherapy alone. Ten patients were followed up after 9-114 months, with an average of 41 months and a median of 26 months. Five patients survived and five died of the disease within two years. Conclusions: PSSL is rare and has a broad morphological spectrum. IHC and molecular tests are needed for definitive diagnosis. Compared with current commonly used IHC markers, SS18-SSX fusion antibody has better sensitivity to PSSL, which could be used as an alternative for FISH, reverse transcription-polymerase chain reaction or next generation sequencing in the diagnosis of PSSL.