# Primary Synovial Sarcoma of the Mediastinum : A Case Report

Authors: Gayatri Ravikumar; Shalini Mullick; Anuradha Ananthamurthy; Marjorie Correa
Journal: Case Reports in Surgery
 (2011)

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## Abstract

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


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## Body

## 1. Introduction

Synovial sarcoma is a distinctive malignant soft tissue neoplasm that commonly occurs in the extremities of young adults. Although frequently associated with joints, tendons and bursal structures, it is now believed that this tumour does not originate from synovial cells as originally postulated. In fact, these tumours show epithelial differentiation and are thought to be derived from pluripotent mesenchymal cells  capable of epithelial differentiation [1].Uncommonly, synovial sarcomas have been reported from rare sites such as head and  neck region, abdomen, thoracic cavity, and mediastinum. We have described here a  case of biphasic synovial sarcoma occurring primarily in the mediastinum. The mediastinum is a rare site for occurrence of a primary synovial sarcoma with only a   few case reports and series published in the literature till date. A wide range of  tumours occur in the mediastinum, and the differential diagnosis of these tumours can  be quite challenging.


## 2. Case Report

A 42-year-old man presented with symptoms of right-sided chest pain, not related to    physical activity or exertion. He also complained of shortness of breath on exertion.  There was no history of cough, fever, or weight loss. Physical examination did not  reveal anything significant. His haematological parameters were normal. The chest  radiograph (PA view) showed a well-defined radio opaque shadow with no  calcification or cavitations with its medial border merging with the right border of the  heart, which was suggestive of an anterior mediastinal mass (Figure1(a)).  Lateral view    confirmed the anterior mediastinal location of the mass (Figure 1(b)). An axial CT scan  showed a heterogeneously enhancing right anterior mediastinal mass with areas of  necrosis which was adherent to the pericardium (Figure 2). Bronchoscopic  examination showed extrinsic compression of the trachea and the right main  bronchus. With a provisional clinical diagnosis of a lymphoma versus a teratoma,  surgical excision was planned through an anterolateral approach. Per operatively, a  6 × 7 cm mass was found in the anterior mediastinum which had a smooth surface. The  mass showed plenty of adhesions to the right lung and pleura. The mass was removed  in piecemeal and was sent with a portion of the lung for histopathological evaluation.Chest radiographs, PA (a) and lateral views (b) show a well-defined mass in the anterior mediastinum.
(a)(b)Axial post-contrast CT scan of the chest showing areas of necrosis in the mass with adherence to the pericardium.
(a)(b)The gross specimen consisted of about 250 gm of grey white soft tissue with  extensive areas of necrosis. Also received was a lobe of lung measuring 9 × 9 × 2 cm.   On microscopic examination, a biphasic neoplasm was noted with well formed  glandular epithelial structures admixed with a spindle cell component (Figure3). The  spindle cell component was monomorphous and showed a fascicular arrangement.  The cells showed elongated vesicular nuclei with mild to moderate nuclear atypia.  Mitosis ranged from 3–5 per 10 high power fields. The glandular spaces were lined by  cuboidal cells with vesicular nuclei and moderate cytoplasm and showed eosinophilic  secretions within their lumens which stained positively with the Alcian blue stain  (Figure 4). The toluidine blue stain failed to reveal any mast cells. There were foci of  calcification and also large areas of necrosis and haemorrhage. The lung parenchyma  and pleura showed no evidence of infiltration by tumour.Photomicrographs showing the spindle cell (a) and the epithelial components (b) of the neoplasm (×100, H&E).
(a)(b)Photomicrographs highlighting the glandular features of the tumour (a) with Alcian blue positivity in the lumen (b) (×400, H&E; ×100, Alcian blue, resp.).
(a)(b)On immunohistochemistry, the glandular component showed cytoplasmic positivity  for the epithelial markers cytokeratin and epithelial membrane antigen (EMA). The spindle cell component stained strongly with vimentin and bcl-2 (Figure5). The tumour did not stain with leucocyte common antigen LCA, desmin, S100, smooth muscle actin (SMA), CD34, or CD99. The proliferation marker Ki67 showed nuclear positivity in up to 10% of the tumour cells. With the combination of histopathological features and immunohistochemical findings, a diagnosis of a primary synovial sarcoma of the mediastinum was offered. The patient received adjuvant chemotherapy with Ifosphamide and Doxorubicin. Eight months later, he presented again with distant metastasis.Immunohistochemistry showing positivity for EMA (a) and Bcl-2 (b) (×400 and ×200, resp.).
(a)(b)


## 3. Discussion

Synovial sarcoma is a rare and aggressive malignant soft tissue tumour occurring  most commonly in the extremities of young adults. Other sites from which this  tumour has been reported include the lung, pleura, chest wall and very rarely, the  mediastinum [2–6]. Only a few case reports, and series of  primary mediastinal synovial  sarcoma are described in the literature so far. A vast array of tumours occur in the  mediastinum, both primary and secondary, and the diagnosis of a primary mediastinal  synovial sarcoma can be challenging.Witkin et al. for the first time in 1989 reported 4 cases of biphasic synovial sarcomas  of the mediastinum [4]. The patients were all adult males, and the tumours were  frequently adherent to the adjacent pleura or pericardium but none were arising from  them. Keratin positivity was seen in the epithelial elements and vimentin positivity in  the spindle cell elements of these tumours. Adherence to the pleura was a feature  noted in our case also. In addition to immunohistochemistry, molecular genetic  analysis may be performed to demonstrate the t(x;18) translocation [6]. A series of 15 cases  of primary synovial sarcomas were reported by Suster and Moran. They described the clinicopathological, immunohistochemical, and ultrastructural features  of these tumours. Nine of their cases presented with anterior mediastinal masses with  chest pain and shortness of breath, in a way similar to our case. The rest showed a  posterior mediastinal location. Five of their cases showed a biphasic appearance, the  rest being monophasic. Immunohistochemistry done on 10 cases showed focal  positivity for cytokeratin and/or epithelial membrane antigen (EMA) and strong  positivity for vimentin and bcl-2 in the spindle cells. Our case also showed strong  positivity for vimentin and bcl-2 in the spindle cell areas with focal cytokeratin and  EMA positivity in the glandular elements.The differential diagnosis of a primary synovial sarcoma in the mediastinum is  complex as a wide array of primary and metastatic tumours occur in this site. The  biphasic synovial sarcoma must be distinguished from metastatic sarcomatoid  carcinoma and biphasic malignant mesothelioma. In a sarcomatoid carcinoma, the  spindle cells as well as the epithelial elements show atypical features. The glandular  structures in a synovial sarcoma do not exhibit much pleomorphism. Biphasic  mesothelioma can show morphological features very similar to a biphasic synovial  sarcoma. However grossly, a mesothelioma presents as diffuse plaque like tumour  masses on the pleural or pericardial surfaces, whereas a synovial sarcoma presents as a discrete mass in the mediastinum. Our case presented as a discrete mass in the   mediastinum and showed adhesions to the pleura. Other spindle cell tumours that  commonly occur in the mediastinum like solitary fibrous tumour and malignant  peripheral nerve sheath tumour (MPNST) were excluded in this case, as the tumour  cells were negative for CD34 and S100 respectively. The gross findings in  combination with the morphological and immunohistochemical profile confirmed the  diagnosis of a synovial sarcoma in our case.Bcl-2 is the product of a mitochondrial oncogene which inhibits apoptosis. This  oncoprotein is  found to be expressed in a variety of benign and malignant spindle cell  tumours of the skin and soft tissue [7]. Its greatest diagnostic usefulness, however,  seems to be in synovial sarcoma and solitary fibrous tumour. However, the latter also  shows positivity for CD34 which is not seen in synovial sarcoma.Synovial sarcomas are highly aggressive tumours, and complete surgical excision  remains the mainstay of treatment. Radiotherapy is often required to obtain local  control of the disease with adjuvant chemotherapy. Adequate pre operative work up such as a fine needle aspirate (FNA) or a needle biopsy might have offered a clue to the diagnosis in this case perhaps leading to better preoperative planning anden bloc resection of the mass.In conclusion, synovial sarcoma must be entertained in the differential diagnosis of  spindle cell as well as biphasic tumours arising in the mediastinum. This case report  emphasizes the importance of prompt clinical suspicion, accurate histopathological  diagnosis, and use of appropriate immunohistochemical markers in the diagnosis of  this unusual tumour in an unusual site.



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*Source: 602853-2011-09-07.xml*