Synovial sarcoma of the pleura and its differentiation from other primary pleural tumours: a clinicopathological and immunohistochemical review of three cases

Mesenchymal tumours of the pleura: review and update

Primary mesenchymal tumours of the pleura are uncommon and can be diagnostically challenging due to their overlapping histopathologic and immunophenotypic features. Herein we discuss selected mesenchymal tumours of the pleura, including solitary fibrous tumour, calcifying fibrous tumour, desmoid fibromatosis, synovial sarcoma, schwannoma, malignant peripheral nerve sheath tumour, inflammatory myofibroblastic tumour, follicular dendritic cell sarcoma, epithelioid hemangioendothelioma, and desmoplastic small round cell tumour. We review their clinicopathologic characteristics, along with an update on the relevant immunohistochemical and molecular features.

Primary Pericardial Synovial Sarcoma: A Case Report and Literature Review

We report a case of a 52-year-old woman who was referred to our institution with a superior vena cava syndrome and was investigated through echocardiography, CT and MRI revealing a well-defined, encapsulated pericardial mass. The pathology, correlated with the immunohistochemical analysis, concluded it was an extremely rare primary pericardial synovial sarcoma. The patient underwent surgery and chemotherapy with a 16-month disease-free survival and passed away after a contralateral aggressive relapse. Moreover, we discuss the role of each imaging modality together with their pericardial synovial sarcoma reported features.

Pediatric Primary Pleural Synovial Sarcoma: A Unique Case Report with Brief Review of Literature

Synovial sarcoma (SS) primary to the pleura is an extremely rare tumor. So far, only nine cases have been reported in pediatric patients. However, none of these patients was found to have a conglomeration of tumors. Here, we report a case of 16-year-old female with monophasic SS and synchronous occurrence of left paraspinal ganglioneuroma and a right paraovarian cystadenoma. A next-generation sequencing genetic panel revealed a novel variant of unknown significance in the MET gene. The occurrence of multiple different tumors in a young patient with a novel genetic variant in a known oncogene (MET) may suggest a possibility of a hitherto unknown cancer predisposition syndrome. We also present a brief review of primary pleural SS reported in pediatric patients.

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.

Primary monophasic synovial sarcoma of the pleura: Neoadjuvant chemotherapy followed by complete resection

We describe a rare case of primary pleural synovial sarcoma in a 27-year-old man with a 4-month history of dry cough and left-sided chest pain. A CT scan showed a large cystic mass in the left pleural cavity. The patient underwent two video-assisted thoracoscopic biopsies and the diagnosis of synovial sarcoma of the pleura was established. After neoadjuvant chemotherapy, which resulted in a partial response, the tumor was completely resected with extrapleural pneumonectomy. Pathological findings showed less than 5% of viable cancer and free surgical margins. The patient is clinically well 24 months after surgery, with no evidence of recurrent disease.

Large primary pleural synovial sarcoma with severe dyspnea: a case report

BACKGROUND

Synovial sarcoma is a malignant neoplasm of soft tissues. It occurs mainly in the extremities and is closely related to tendons, tendon sheaths, and bursal structures. Primary synovial sarcoma of the pleura and lungs is extremely rare.

CASE PRESENTATION

We present the case of a 62-year-old man with a large synovial sarcoma of the left pleura. He presented with general fatigue and severe dyspnea. Chest computed tomography (CT) revealed a 20-cm tumor in the left thoracic cavity. We first diagnosed the tumor as a sarcomatoid mesothelioma based on CT-guided needle biopsy. We speculated that his severe dyspnea was because of ventilation-perfusion mismatch due to the left pulmonary collapse. Furthermore, we thought that there was a discrepancy between the CT findings and the pathological findings from the biopsy specimen. We performed pleuropneumonectomy through an anterior approach with median sternotomy and 5th-intercostal thoracotomy. The resected specimen contained a 22-cm pleural tumor with parenchymatous hemorrhage. We diagnosed the tumor as monophasic synovial sarcoma based on its morphologic and immunohistochemical features. We suspected there was microscopic residual tumor in the left diaphragm and therefore performed radiation therapy. After radiotherapy, he received adjuvant chemotherapy with ifosfamide and Adriamycin. One year after surgery, the patient is alive with no signs of tumor recurrence.

CONCLUSIONS

We report a case of a large synovial sarcoma of the pleura in a patient with severe dyspnea. He was treated with pleuropneumonectomy, radiotherapy, and adjuvant chemotherapy. Although the best treatment for this rare condition has not been defined, we thought that tumor resection and adjuvant therapy were appropriate to control the disease in this case.

Primary Pleuropulmonary Synovial Sarcoma on Fluorodeoxyglucose Positron Emission Tomography-Computed Tomography Scan

Primary pleuropulmonary synovial sarcoma, a mesenchymal tumor of lung and pleura, is very rare and highly aggressive condition among the primary lung malignancies. As role of fluorodeoxyglucose positron emission tomography-computed tomography (FDG PET-CT) has been established in lung malignancies in terms of staging, restaging, biopsy guidance, and treatment response evaluation, there is also role of FDG PET-contrast-enhanced CT (CECT) to raise suspicion or increase confidence in reporting of sarcomatous lung malignancy by studying characteristics of CECT scan features. We present a case of a 57-year-old female patient having large lung mass, who underwent FDG PET-CT scan and findings raised strong suspicious of noncarcinomatous pattern of lung mass and may have sarcomatous primary lung malignancy which was later proven on histopathological and immunohistochemistry report.

Pleural synovial sarcoma patient treated with combined chemotherapy and Endostar, plus sunitinib maintenance therapy: A case report and review of the literature

Synovial sarcoma is a rare, highly malignant soft-tissue tumor that occurs primarily in the extremities. At present, there is no effective clinical treatment for this condition. The present study reports the case of a 49-year-old male who was diagnosed with pleural synovial sarcoma and treated with recombinant human endostatin (Endostar) combined with chemotherapy for a total of six cycles, followed by sunitinib maintenance therapy. To the best of our knowledge, this is the first reported use of sunitinib for maintenance therapy in pleural synovial sarcoma. The patient survived for 25 months after the recurrence of the disease following surgery. The results indicate that this combination therapy was effective in the treatment of pleural synovial sarcoma. The present study also briefly reviews the literature on pleural synovial sarcoma, and the features and treatments for this rare case are discussed.

Primary pulmonary synovial sarcoma requiring differentiation from pulmonary metastasis of tibial adamantinoma: a case report

Background

Primary pulmonary synovial sarcoma (PPSS) is rare. We describe a case of PPSS complicated by tibial adamantinoma that required differentiation from lung metastasis.

Case presentation

A 39-year-old Japanese woman presented with hemoptysis, dyspnea, and a well-defined tumor measuring 3.0 cm in greatest diameter in the right lower lobe on chest computed tomography (CT). Positron emission tomography/CT with fluorodeoxyglucose (FDG-PET/CT) showed mild uptake of FDG (maximum standardized uptake value of 2.0). Her past history included surgery for adamantinoma of the right tibia at age 25 years. We considered the possibility of pulmonary metastasis from the adamantinoma and performed fluoroscopy-assisted thoracoscopic resection of the tumor after CT-guided Lipiodol marking. Histologically, the tumor was composed mainly of a dense proliferation of spindle cells. Immunohistochemical studies were positive for epithelial membrane antigen, B cell lymphoma 2, and transducing-like enhancer of split 1. They were negative for CD34. The synovial sarcoma, X breakpoint 1 gene-fusion transcript was detected by reverse transcription-polymerase chain reaction. It is diagnostic of PPSS. Resection margins were negative. The patient was well without evidence of recurrence or metastasis of the PPSS or adamantinoma at the 30-month and 15-year follow-ups.

Conclusion

Clinical and radiological manifestations of PPSS overlap with those of other lung tumors. The solitary pulmonary nodule in this case was indistinguishable from pulmonary metastases of the adamantinoma based on clinical symptoms, epidemiology, chest radiography, CT, and FDG-PET/CT. PPSS was diagnosed only after evaluating gross pathology, histology, immunohistochemistry, and cytogenetics. PPSS should be included in the differential diagnosis of a well-defined homogeneous round or oval lung mass. To our knowledge, this is the first report of PPSS complicated by adamantinoma.

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.

Tumors that mimic asbestos-related mesothelioma: time to consider a genetics-based tumor registry?

The diagnosis of mesothelioma is not always straightforward, despite known immunohistochemical markers and other diagnostic techniques. One reason for the difficulty is that extrapleural tumors resembling mesothelioma may have several possible etiologies, especially in cases with no meaningful history of amphibole asbestos exposure. When the diagnosis of mesothelioma is based on histologic features alone, primary mesotheliomas may resemble various primary or metastatic cancers that have directly invaded the serosal membranes. Some of these metastatic malignancies, particularly carcinomas and sarcomas of the pleura, pericardium and peritoneum, may undergo desmoplastic reaction in the pleura, thereby mimicking mesothelioma, rather than the primary tumor. Encasement of the lung by direct spread or metastasis, termed pseudomesotheliomatous spread, occurs with several other primary cancer types, including certain late-stage tumors from genetic cancer syndromes exhibiting chromosomal instability. Although immunohistochemical staining patterns differentiate most carcinomas, lymphomas, and mestastatic sarcomas from mesotheliomas, specific genetic markers in tumor or somatic tissues have been recently identified that may also distinguish these tumor types from asbestos-related mesothelioma. A registry for genetic screening of mesothelioma cases would help lead to improvements in diagnostic criteria, prognostic accuracy and treatment efficacy, as well as improved estimates of primary mesothelioma incidence and of background rates of cancers unrelated to asbestos that might be otherwise mistaken for mesothelioma. This information would also help better define the dose-response relationships for mesothelioma and asbestos exposure, as well as other risk factors for mesothelioma and other mesenchymal or advanced metastatic tumors that may be indistinguishable by histology and staining characteristics.

Challenges and controversies in the diagnosis of malignant mesothelioma: Part 2. Malignant mesothelioma subtypes, pleural synovial sarcoma, molecular and prognostic aspects of mesothelioma, BAP1, aquaporin-1 and microRNA

Pleural malignant mesothelioma (MM) includes several unusual and even rare but distinctive histological subtypes, in addition to the usual subdivision into epithelioid, biphasic and sarcomatoid MM. Criteria for discrimination between fibrous pleuritis versus desmoplastic mesothelioma include evidence of neoplastic invasion for diagnosis of desmoplastic MM, but this histological assessment is complicated by the recently-described 'fake fat phenomenon' in cases of fibrous pleuritis. The distinction between biphasic and monophasic synovial sarcoma of the pleura versus biphasic and sarcomatoid MM can be problematical and is most cogently based upon molecular detection of the t(X;18) translocation, whereas a clear diagnosis of MM for a pleural tumour histologically resembling synovial sarcoma is favoured by a negative result for this translocation and, probably, microRNA evidence supportive of a diagnosis of MM. Aquaporin-1 (AQP1) is a molecule involved in the growth of MM cells, and yet is a factor reported to correlate with improved survival rates for MM with an epithelioid component, in comparison to AQP1-poor MM, as assessed from AQP1 expression by epithelioid MM cells only (apart from co-expression by stromal endothelial cells in addition to the tumour cells). Recent reports have also focused upon germline mutations in the BRCA1-associated protein 1 (BAP1), not only in cases of familial mesothelioma, but also BAP1 deletion in sporadic MM. Prognostic factors for MM include not only the histological subtypes, but other independent variables that include (among others), AQP1 expression by mesothelioma cells, the clinical status of the patient, the serum neutrophil:lymphocyte ratio and blood thrombocytosis.

Rare pleural tumors

Primary pleural tumors other than mesothelioma account for fewer than 1% of all lung cancers, and consequently they pose diagnostic and management challenges. Their treatment must be targeted toward the specific tumor type and is often quite different from the treatment for mesothelioma or metastases. Despite the best efforts at diagnosing and treating these tumors, the prognosis associated with some of the benign and many of the malignant variants of these tumors remains poor. In this review, we describe the radiologic and pathologic features of the less common primary pleural tumors and propose a diagnostic approach to their evaluation.

Synovial sarcoma of the head and neck: rare case of cervical metastasis

BACKGROUND

Synovial sarcoma is a rarely encountered soft tissue sarcoma. Surgery with a wide surgical margin is the treatment of choice. However, there is no consensus on the treatment of head and neck synovial sarcoma in patients with cervical metastasis.

METHODS

A 20-year-old man was seen with a palpable mass in the right neck. He had been diagnosed with synovial sarcoma of the right tonsil and treated by surgery 1 and a half years before; therefore, the mass detected was thought to be a cervical metastasis of synovial sarcoma. We performed a modified radical neck dissection with no postoperative treatment. The pathological diagnosis was confirmed by detecting the SS-specific fusion gene SYT-SSX1.

RESULTS

The patient remains free of recurrence or metastasis 2 years and 10 months after the surgery.

CONCLUSIONS

We encountered a case of head and neck synovial sarcoma with cervical metastasis that was successfully treated.

Primary 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. Pleuropulmonary synovial sarcoma can 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 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 gadoliniumbased contrast material such as gadopentetate dimeglumine. Current treatment consists of surgical resection followed by chemotherapy, radiation therapy, or both.

Problems in mesothelioma diagnosis

Many centres are now seeing increasing numbers of patients with malignant mesothelioma. This presents pathologists involved in making the diagnosis with a number of problems, which can be divided into those encountered in making the distinction between mesothelioma and benign changes and those experienced in separating mesotheliomas from other types of epithelial and connective tissue tumours. Immunohistochemistry plays a major role in helping to make the diagnosis, but it should be interpreted with due regard to the clinical setting and radiological features, and with a knowledge of the wide morphological variations seen in mesothelioma. This review identifies some of these problems and addresses the uses and limitations of immunohistochemistry in different situations. It includes a discussion of some of the less common variants of mesothelioma and other pleural-based tumours that enter into the differential diagnosis.

Immunohistochemistry of pulmonary and pleural neoplasia

CONTEXT

The use of immunohistochemical stains has several applications in the evaluation of pulmonary and pleural neoplasms. The number of available immunohistochemical stains is continually expanding and, although these stains are an important diagnostic adjunct, their use is not without limitations and pitfalls.

OBJECTIVE

To review and summarize the primary immunohistochemical applications with regard to the most common pulmonary and pleural neoplasms and discuss newly developed markers and common pitfalls.

DATA SOURCES

Pertinent peer-reviewed literature emphasizing immunohistochemical applications in common lung and pleural tumors, unusual and problematic staining patterns in frequently encountered subtypes/histologic variants, and recently developed immunohistochemical stains of potential promise.

CONCLUSIONS

Immunohistochemical stains provide the greatest aid in establishing the site of origin of adenocarcinomas encountered in the lung and in separating epithelioid mesothelioma from adenocarcinoma. Certain subtypes of pulmonary adenocarcinomas may exhibit unusual staining patterns that may be potentially problematic. Immunohistochemistry has a more limited role in separating small cell carcinoma from non-small cell carcinoma, and extreme caution must be used in the situation of crushed biopsy specimens.

Primary pleural neoplasia: entities other than diffuse malignant mesothelioma

CONTEXT

Overwhelmingly, the most common neoplasm involving the pleura is metastatic carcinoma. In contrast, diffuse malignant mesothelioma occurs relatively rarely; however, it is nonetheless the most common neoplasm primary to the pleura. Metastatic carcinoma and diffuse malignant mesothelioma each have their own prognostic and therapeutic characteristics. Other primary pleural neoplasms occur uncommonly or rarely, with their own prognostic and therapeutic characteristics.

OBJECTIVE

To review primary pleural neoplasms other than diffuse malignant mesothelioma, to better ensure correct diagnosis and optimal assessment of prognosis and treatment.

DATA SOURCES

Literature review and primary material from the authors' institutions.

CONCLUSIONS

A nonexhaustive group of uncommon to rare benign and malignant primary pleural neoplasms--other than diffuse malignant mesothelioma--are presented, of which one must be aware in order to maintain an appropriate index of suspicion to include them in the differential diagnosis of a pleural tumor.

The diagnostic value of SYT-SSX detected by reverse transcriptase-polymerase chain reaction (RT-PCR) and fluorescence in situ hybridization (FISH) for synovial sarcoma: a review and prospective study of 255 cases

This study aimed to evaluate the diagnostic value of SYT-SSX detected by reverse transcriptase-polymerase chain reaction (RT-PCR) and fluorescence in situ hybridization (FISH) for synovial sarcoma (SS) in known and potential cases. SYT-SSX was analyzed in formalin-fixed, paraffin-embedded tissues of 62 known SS, 60 non-SS and 133 potential SS by RT-PCR and FISH. FISH was mainly performed on a tissue microarray with some modifications. SYT-SSX was detected in 94.7% (54/57) of known SS and 70.5% (86/122) of potential SS by RT-PCR and in 96.7% (58/60) of known SS and 78.1% (100/128) of potential SS by FISH. Moreover, SYT-SSX was negative in 100% (58/58) of non-SS by RT-PCR and in 100% (59/59) of non-SS by FISH. Accordingly, SYT-SSX was detected in 106 potential SS by RT-PCR or FISH, including 80 cases manifested by both methods, 20 specimens verified only by FISH and 6 samples confirmed only by RT-PCR. Clinical findings and immunohistochemistry data were analyzed in potential SS with final molecular diagnosis. The positive ratio of cytokeratin (CK) and epithelial membrane antigen (EMA) in finally diagnosed SS was 51.9% (55/106) and 61.3% (65/106), respectively. Except EMA, clinical parameters (age, sex, tumor size, tumor sites) and other immunohistochemistry indexes (CK, S-100, neurone specific enolase (NSE), CD99, myoglobin, smooth muscle actin (SMA), cluster of differentiation (CD) 68 and mesothelial cell) had no significant difference between finally diagnosed SS and non-SS. It is indicated that the efficiency of FISH is comparable to or even higher than that of RT-PCR for SYT-SSX detection. The detection of SYT-SSX by RT-PCR or FISH is very useful for the final diagnosis of potential synovial sarcomas.

Primary pulmonary and mediastinal synovial sarcoma: a clinicopathologic study of 60 cases and comparison with five prior series

Primary pulmonary and mediastinal synovial sarcoma is rare and poses a diagnostic challenge particularly when unusual histological features are present. We present 60 cases of primary pulmonary and mediastinal synovial sarcoma (29 male and 27 female subjects; mean age, 42 years) and compare our results with five prior series to better define unusual histological features. Clinically, patients with mediastinal synovial sarcoma were younger with a male gender bias. Radiologically, tumors were well delineated with distinctive magnetic resonance imaging features and little vascular enhancement. In all, 21/46 patients died of disease within 5 years. Histologically, all tumors had dense cellularity, interlacing fascicles, hyalinized stroma, and mast cell influx. Hemangiopericytoma-like vasculature (48/60), focal myxoid change (30/60), and entrapped pneumocytes (23/60) were seen. Calcification was not prevalent (10/60). Unusual histological features included Verocay body-like formations (7/60), vague rosettes (6/60), well-formed papillary structures (3/60), adenomatoid change (3/60), and rhabdoid morphology (2/60). Immunohistochemistry demonstrated expression of pancytokeratin (39/58), epithelial membrane antigen (29/53), cytokeratin 7 (26/40), cytokeratin 5/6 (5/7), calretinin (15/23), CD99 (19/23), bcl-2 (24/24), CD56 (11/11), S-100 (9/51), and smooth muscle actin (8/32). In total, 92% (36/39) of primary pulmonary and mediastinal synovial sarcomas studied were positive for t(x;18). In conclusion, our study confirms the clinical, histological, immunohistochemical, and molecular data from previous large series of primary pulmonary and mediastinal synovial sarcoma. Compared with soft tissue synovial sarcoma, primary pulmonary and mediastinal synovial sarcoma has less calcification, less obvious mast cell influx, and less radiologic vascularity, but similar magnetic resonance imaging features, percentage of poorly differentiated tumors, and number of t(x;18)-positive tumors. Awareness of focal unusual histology can prevent misdiagnosis particularly in t(x;18)-negative tumors.

SYT-SSX fusion is absent in sarcomatoid mesothelioma allowing its distinction from synovial sarcoma of the pleura

The diagnosis of sarcomatoid mesothelioma is still a worldwide challenge and it is often difficult, both clinically and by morphological analysis, to differentiate sarcomatoid mesothelioma from synovial sarcoma, the most frequent intrathoracic sarcoma. To confirm the absence of the synovial sarcoma translocation t(X; 18) (SYT-SSX) in sarcomatoid mesothelioma, and to test its usefulness differentiating sarcomatoid mesothelioma from synovial sarcoma, 28 tumours were examined using the reverse transcriptase-polymerase chain reaction. RNA was extracted from paraffin blocks using standard methods, reverse-transcribed and PCR performed. Molecular analysis completed in two independent laboratories showed that sarcomatoid mesothelioma samples were negative for the t(X-18). This result confirms the usefulness of this analysis in differentiating sarcomatoid mesothelioma from synovial sarcoma.

Applications and limitations of immunohistochemistry in the diagnosis of malignant mesothelioma

Malignant mesothelioma is an uncommon malignant epithelial neoplasm originating from the serosal surface of body cavities. Because serosal surfaces are a common site of metastatic spread for a variety of malignant neoplasms originating from internal organs, separating malignant mesothelioma from metastatic tumors is of clinical importance. The diagnosis of malignant mesothelioma is complex and usually requires a multimodal approach that includes careful clinical history and physical examination, imaging studies, and tissue sampling for multimodal evaluation including routine histology, histochemistry, electron microscopy, and immunohistochemical tests. Of these, immunohistochemistry has emerged as the most valuable and readily available modality for the routine evaluation of these tumors. Unfortunately, no specific antibodies have yet been developed that can be accepted as exclusive for these tumors. The immunohistochemical diagnosis of malignant mesothelioma therefore depends on the use of a panel of stains that includes markers that are commonly expected to react with these tumors ("positive" markers) and markers that are not commonly expected to react with these tumors ("negative" markers). Additionally, the selection and utility of these various markers can vary considerably based on a constellation of circumstances, including patient sex, histologic appearance of the tumor (ie, epithelioid vs. sarcomatoid, etc), and various other clinical circumstances. Herein, we will review the currently available immunohistochemical markers used for the diagnosis of malignant mesothelioma and offer suggestions for the use of appropriate panels of stains based on specific morphologic types and clinical circumstances.

Resected case of synovial sarcoma in the pleural cavity

A 29-year-old female was admitted to our hospital complaining of severe dry cough and low-grade fever. A chest roentgenogram and a chest computed tomographic scan revealed a huge tumor and massive pleural effusion in the left pleural cavity. Pathological examination revealed spindle shaped malignant cells. SYT-SSX fusion gene transcripts were detected, so we diagnosed the tumor as a synovial sarcoma in the pleural cavity. After neoadjuvant chemotherapy we resected the tumor completely. A synovial sarcoma in the pleural cavity is extremely rare. To the best of our knowledge, this is the thirteenth case, and the first case to undergo neoadjuvant chemotherapy and complete resection. Because a synovial sarcoma in the pleural cavity has a poor prognosis and is characterized by a high incidence of recurrence, we must carefully follow up this patient.

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.

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.

Review and update of uncommon primary pleural tumors: a practical approach to diagnosis

OBJECTIVE

We address the current classifications and new changes regarding uncommon primary pleural tumors. Primary pleural tumors are divided according to their behavior and are discussed separately as benign tumors, tumors of low malignant potential, and malignant neoplasms.

DATA SOURCES

Current literature concerning primary pleural neoplasms was collected and reviewed.

STUDY SELECTION

Studies emphasizing clinical, radiological, or pathologic findings of primary pleural neoplasms were obtained.

DATA EXTRACTION

Data deemed helpful to the general surgical pathologist when confronted with an uncommon primary pleural tumor was included in this review.

DATA SYNTHESIS

Tumors are discussed in 3 broad categories: (1) benign, (2) low malignant potential, and (3) malignant. A practical approach to the diagnosis of these neoplasms in surgical pathology specimens is offered. The differential diagnosis, including metastatic pleural neoplasms, is also briefly addressed.

CONCLUSIONS

Uncommon primary pleural neoplasms may mimic each other, as well as mimic metastatic cancers to the pleura and diffuse malignant mesothelioma. Correct diagnosis is important because of different prognosis and treatment implications for the various neoplasms.

Radiofrequency thermal ablation of primary pleural synovial sarcoma

Percutaneous radiofrequency (RF) thermal ablation has received attention as an effective minimally invasive approach for the treatment of a variety of neoplasms. However, the therapeutic efficacy of RF thermal ablation on primary pleural synovial sarcoma has not yet been reported. A 76-year-old man with a primary pleural synovial sarcoma who was medically inoperable received RF thermal ablation to achieve local control. Therefore, an RF electrode was inserted into the lesion and connected to an RF generator. In this report, a case of successful treatment of a primary pleural synovial sarcoma using RF ablation without complication is presented.

Primary Intrathoracic Synovial Sarcoma

Synovial sarcoma (SS), an aggressive neoplasm accounting for up to 14% of soft tissue sarcomas, was recently recognized as a primary tumor in the lung and pleura. SS is characterized by the chromosomal translocation t(X;18)(SYT-SSX) found in more than 95% of the tumors. We report a cooperative study from the French Sarcoma Group and the Mesopath Group on 40 t(X;18)(SYT-SSX)-positive primary intrathoracic SS. There were 22 males and 18 females, whose age ranged from 16 to 79 years (median, 47 years). Neoplasms were mostly circumscribed and of large size (median, 7.5 cm; range, 2-16 cm). Thirty-nine tumors were monophasic SS, including 24 (60%) monophasic fibrous and 15 (37.5%) poorly differentiated cases, and one lesion was a biphasic SS. A larger proportion of poorly differentiated tumors were observed among intrathoracic SS as compared with soft tissue SS. Immunohistochemically, 90% of the cases reacted with at least one epithelial marker. CD34 was focally expressed in 3 cases. SYT-SSX1 fusion transcripts were detected in 22 cases (56.4%) and SYT-SSX2 fusion transcripts in 17 cases. Median and 5-year disease-specific survival in 33 patients was 50 months and 31.6%. Median and 5-year disease-free survival was 24 months and 20.9%. Patient sex, age, tumor size, histologic subtype, grade, and SYS-SSX fusion type had no significant impact on outcome. In conclusion, intrathoracic SS are rare but aggressive tumors with poor prognosis. In this unusual location, the detection of SYT-SSX fusion transcripts is a valuable diagnostic adjunct.

Primary synovial sarcoma of the pleura: beware of misdiagnosis

Primary synovial sarcoma of the pleura is an uncommon entity in the present medical literature. However, the paucity of documented cases may be due to misdiagnoses as a malignant mesothelioma in the past. Early diagnosis with new molecular techniques may improve the outcome of this tumour, which is believed to have a grave prognosis at present.

Pathology of mesothelioma

In this article, progress in distinguishing mesothelioma from mesothelial hyperplasia and fibrosing pleuritis was discussed. Advances in the immunohistochemical characterization of mesothelioma, in the recognition of entities that mimic mesothelioma, and in their distinction from mesothelioma were reviewed. Cytogenetic and molecular genetic contributions to the diagnosis of pleural synovial sarcoma were briefly summarized. The diagnosis of epithelial type mesothelioma can be established in most cases. Several mesotheliomas, however, especially rare subtypes, and sarcomatoid, desmoplastic, and poorly differentiated mesotheliomas continue to present diagnostic challenges.

Primary poorly differentiated monophasic synovial sarcoma of the lung. A case report with immunohistochemical and genetic studies

We describe a case of a poorly differentiated monophasic synovial sarcoma arising in the lung of a 50-year-old man. The tumor, which was located in the right upper lobe, was lobulated, relatively well-circumscribed, and whitish to yellowish in color. Microscopically, it was composed exclusively of ovoid to polygonal or short spindle cells, with a high nuclear to cytoplasmic ratio and relatively scant cytoplasm, arranged in solid sheets or in a hemangiopericytomatous pattern with intervening wiry collagen fibers. At the periphery of the tumor, entrapped benign alveolar epithelium produced a pseudo-biphasic appearance. In some areas, an abundance of keloidal collagen imparted a close resemblance to a solitary fibrous tumor, making it difficult to establish the diagnosis on the initial needle biopsy, although the malignant nature of the tumor was suggested because of nuclear anaplasia. Immunohistochemically, the tumor was positive for cytokeratin AE1/AE3, CAM5.2, EMA, vimentin, bcl-2 protein, calretinin, and CD34. The reverse transcriptase-polymerase chain reaction (RT-PCR), using RNA extracted from fresh-frozen tissue, demonstrated SYT/SSX-1 fusion transcripts, confirming the diagnosis of synovial sarcoma. Microscopic examination demonstrated metastatic deposits in hilar lymph nodes. This case indicates that a primary pulmonary synovial sarcoma, particularly in its poorly differentiated form, is a diagnostically challenging and highly aggressive neoplasm typically found at an advanced stage.

Intraneural synovial sarcoma: two cases

We report two cases of intraneural synovial sarcoma. The first patient is a 46-year-old female who presented for several months with soft-tissue mass in the right infra-auricular region. The second patient is a 11-year-old girl who fell and then presented with pain in the area innervated by the right C7 spinal root and a nodule identified in the nerve root foramina. Both lesions were of small size and presented with features of synovial sarcoma. A biphasic variant was found in case 1 and a monophasic variant was present in case 2. Immunohistochemical studies were performed to confirm the diagnosis, excluding the main differential diagnoses, namely schwannoma and malignant peripheral nerve sheath tumor. Ultrastructural study was performed in case 2 allowing exclusion of other possible diagnoses. Molecular studies were performed on paraffin-embedded tissue in both cases and revealed the known characteristic t(X;18)(SYT-SSX) translocation.

[Primary renal synovial sarcoma. A new entity in the morphological spectrum of spindle cell renal tumors]

We report 2 primary renal synovial sarcoma. These tumors were formerly designated as embryonal cystic sarcoma of the kidney. Most cases are diagnosed between the ages of 20 and 50 years. Some cases show local recurrence after nephrectomy. On gross examination, tumors are large, partially necrotic, and usually contain cysts. Microscopically, tumors are characterized by monomorphic plump spindle cells. The cysts are lined by mitotically inactive epithelial cells without striking cellular atypia. The spindle cells were immunoreactive for EMA, CD56, and sometimes for CD99. They were non-reactive for desmin, actin, S 100, and cytokeratins. The cyst epithelium is cytokeratin positive. The presence of a SYT-SSX gene fusion resulting from the t(X;18) characteristic for synovial sarcoma was demonstrated by reverse transcriptase polymerase chain reaction in both tumors. Primary renal synovial sarcoma is a distinctive tumor entity, which should be considered in renal tumors consisting of spindle cells.

Should molecular testing be required for diagnosing synovial sarcoma?

BACKGROUND

The t(X;18) translocation is a specific marker of synovial sarcomas (SS). Detection of SYT-SSX transcripts by polymerase chain reaction (PCR) was tested on preselected specimens of well-established histologic types, but to our knowledge, the diagnostic utility of molecular assays on a series of potential SS in comparison with conventional tools has never been reported.

METHODS

Two hundred four consecutive cases of potential SS submitted for a second opinion were studied prospectively. On the basis of clinical context, histologic aspect, and immunohistochemical profile, the tumors were divided into three categories: 1) diagnosis of SS certain, when the only possible diagnosis was SS; 2) diagnosis of SS probable, when SS was the first diagnosis contemplated, but a differential diagnostic issue was raised by other tumors; 3) diagnosis of SS possible, when the diagnosis of SS was not the first diagnosis considered. Detection of SYT-SSX transcripts was performed using real-time PCR from fixed, embedded tissue as a systematic test.

RESULTS

Sufficient RNA samples were recovered for PCR from 177 specimens (87%). One hundred four specimens (51%) were positive for SYT-SSX transcripts. Tumor sites of SS included the extremities (n = 57), lung (n = 13), trunk wall (n = 12), head and neck (n = 6), and other sites (n = 16). There were 61 monophasic, 22 poorly differentiated, 17 biphasic, and 4 predominantly epithelial SS. For 58 tumor specimens (29%), diagnosis of SS was certain before molecular testing; 49 (84.5%) of these 58 contained SYT-SSX transcripts. For 39 tumor specimens (19%), diagnosis of SS was probable; 29 (74.4%) of these 39 contained SYT-SSX transcripts. For 107 tumor specimens (52%), diagnosis of SS was only possible and strongly challenged by another histologic type. The issue consisted mainly of making the distinction between an SS and a poorly differentiated spindle cell sarcoma (n = 49), a poorly differentiated round cell sarcoma (n = 34), a carcinoma (n = 11), a myoepithelioma (n = 8), or an epithelioid fibrosarcoma (n = 5).Twenty-six tumor specimens (24.3%) contained SYT-SSX transcripts-10, 7, 5, 3, and 1 in the spindle cell tumor, round cell tumor, carcinomalike tumor, myoepitheliomalike tumor, and epithelioid-fibrosarcoma-like tumor categories, respectively.

CONCLUSIONS

Molecular testing was not required if the diagnosis of SS was certain or probable on the basis of clinical, histologic, and immunohistochemical evaluation. However, it proved to be very helpful or necessary when the diagnosis of SS was only possible and was challenged by other tumor types, mainly other spindle cell sarcomas, round cell sarcomas, carcinomas, myoepitheliomas, and epithelioid fibrosarcomas.

Synovial sarcoma in older patients: clinicopathological analysis of 32 cases with emphasis on unusual histological features

AIMS

To analyse the clinicopathological features of synovial sarcoma presenting in patients over 60 years of age, an uncommon subset which have not been specifically studied.

METHODS AND RESULTS

Thirty-two cases of primary synovial sarcoma in patients aged > or =60 years were retrieved from the authors' consultation files. These were analysed histologically and immunohistochemically and clinical follow-up was obtained in 26 cases (median duration 41 months). Mean age at diagnosis was 71.6 years (range 60-84) with 19 females and 13 males. Anatomical sites were lower limb (n = 13), upper limb (n = 5), lung/pleura (n = 5), trunk (n = 4), head/neck (n = 3), mediastinum (n = 1) and scrotum (n = 1). Histologically, 23 were monophasic and nine were biphasic; 14 were poorly differentiated, of which five showed focally marked pleomorphism. Unusual features in two cases each included organoid nodules, granular cell change, squamous metaplasia and papillary architecture. Ten patients developed local recurrence and 11 developed metastases, of whom seven died. Large tumour size, poorly differentiated morphology and high mitotic rate correlated with poor outcome.

CONCLUSIONS

Less than 10% of synovial sarcomas occur in patients over 60, in which age group this diagnosis is often not considered. Despite inevitable bias in consultation material, it seems that these cases, when compared with younger age groups, more often show poorly differentiated histology and more often develop at unusual locations.

Primary synovial sarcoma of the chest: radiographic and clinicopathologic correlation

Primary synovial sarcoma of the thorax is rare. Origin of thoracic synovial sarcoma in the pleura or lung was first described only 7 years ago. Radiologic characteristics of this disease have not yet been studied in a formal series. The authors sought to define the radiologic features of primary thoracic synovial sarcoma and to correlate the findings with clinical and pathologic features. They examined clinical, radiologic, and pathologic features of five patients with primary synovial sarcoma of the chest. Radiologic evaluation included conventional radiographs, computed tomographic scans, and magnetic resonance images of the chest. Patients included three men and two women who ranged in age from 28 to 40 years. Primary tumors involved the chest wall (n = 2), lung (n = 1), or both (n = 2). Chest pain was the most common presenting symptom. Although conventional radiographs often showed the lesions to be ill defined, computed tomographic scans showed well-defined masses in every case. Heterogeneous enhancement and an absence of calcification were also seen. Pathologic evaluation demonstrated synovial sarcoma with equal distribution between the monophasic and biphasic variants. The chromosomal translocation X;18 was demonstrated in four of four cases tested. All patients were treated by resection. Recurrence was demonstrated radiologically in four patients at 2 to 14 months. All patients were alive at 9 to 58 months of follow-up. The authors conclude that primary synovial sarcoma of the chest occurs in young adults, most commonly presenting with chest pain. It is characterized radiologically by a heterogeneously enhancing well-defined mass without calcifications.