Journal of Cancer Research and Therapeutics Medknow Publications on behalf of the Association of Radiation Oncologists of India (AROI) ISSN: 0973-1482 EISSN: 1998-4138 Vol. 6, Num. 4, 2010, pp. 564-566

Journal of Cancer Research and Therapeutics, Vol. 6, No. 4, October-December, 2010, pp. 564-566

Case Report

Posterior mediastinal biphasic synovial sarcoma in a 12 year-old boy: A case report and review of literature

Madhumay Pal¹, Bidisha Naskar Ghosh¹, Chhaya Roy¹, Asim Kumar Manna²

¹ Department of Radiotherapy, Institute of Post Graduate Medical Education and Research, and S.S.K.M. Hospital, 244, A.J.C. Bose Road, Kolkata - 700 020, West Bengal, India
² Department of Pathology, Institute of Post Graduate Medical Education and Research, and S.S.K.M. Hospital, 244, A.J.C. Bose Road, Kolkata - 700 020, West Bengal, India

Correspondence Address: Madhumay Pal, 21/1A, R. K. Ghosal Road, Kasba, Kolkata - 700 042, India, madhumay@hotmail.com

Code Number: cr10139

PMID: 21358103

DOI: 10.4103/0973-1482.77075

Abstract

Keywords: Biphasic, mediastinum, synovial sarcoma

Introduction

Synovial sarcoma comprises about 5-10% of all soft tissue sarcomas. Its occurrence as a primary mediastinal neoplasm is very rare. ^[1] Classical synovial sarcoma is a distinctive soft tissue malignant neoplasm of mesenchymal origin, which combines the histological features of both a carcinoma and a sarcoma. ^[2] It may have epithelial cells, mimicking carcinoma, intimately admixed with spindled sarcoma cell. These tumors are seen to occur in adolescents and young adults of 15-40 years of age and more than 85% of synovial sarcomas arise in the extremities, mainly in the lower limbs around the knee. ^[3]

Although this type of tumor has been reported in areas like head and neck, lower back, pleura and peritoneum, synovial sarcoma of the mediastinum is very rare. Reported number of cases of primary synovial sarcoma arising exclusively from mediastinum vary from 4 to 15. ^[1],[2],[4] We report here a case of primary mediastinal biphasic synovial sarcoma along with a review of literature.

Case Report

A boy of 12 years of age presented with left-sided chest pain of about 3 years duration. Chest X-ray [[Figure - 1]a] showed left-sided opacity with loss of cardiac silhouette and mediastinum deviated to the opposite side. Contrast-enhanced computed tomography (CECT) axial scan of thorax [Figure - 2] revealed a large, well-defined, patchily enhancing, heterogeneous mass with smooth margin in the left side of posterior mediastinum, and extending into middle mediastinum. Patchy areas of necrosis and calcification were noted within the mass. Trachea and heart were deviated to the right. No mediastinal lymphadenopathy was seen. Crowding and stretching of vessels were seen in left lung adjacent to the mass. Right lung appeared normal with no focal space occupying lesion (SOL) seen. Mild left-sided pleural effusion with pleural thickening along with mild rib crowding on left upper hemithorax was noted. The impression of computed tomography (CT) scan was a suspicion of teratodermoid. CT guided fine needle aspiration cytology (FNAC) from the mass reported it as spindle cell variant of adenocarcinoma. Ultrasonography (USG) of the whole abdomen revealed no abnormality. His hemogram and blood biochemistry were within normal limits.

The mediastinal tumor was resected by left thorarocotomy. The gross pathology of the tumor on excision was that of a well-circumscribed, encapsulated tumor measuring 14 cm in its greatest axis. The cut surface was grayish and fleshy. Three pathologists opined, in a double-blind histopathological examination, the tumor to be a biphasic synovial sarcoma having a spindle cell component and an epithelial component [[Figure - 3]a and b]. Cleft-like spaces lined by epithelial cells were present. Pseudoglandular structures along with focal areas of calcification were found. Capsule was infiltrated by tumor at places. The mean mitotic count was 7 per 10 high power field (hpf).

Three cycles of combination chemotherapy with ifosfamide and doxorubicin were given. Radiation therapy to the posterior mediastinum is now being given by AP (Antero Posterior)-PA (Postero Anterior) and lateral thoracic wall portals and the patient is now disease free [[Figure - 1]b], 4 months after surgery. We plan to administer three more cycles of chemotherapy with the hope of a long disease free survival.

Discussion

Synovial sarcoma is named so due to its resemblance to developing synovial tissue under light microscopy. ^[2],[3] It arises from the pluripotential mesenchymal cells near joint surfaces, tendons, tendon sheaths, juxta-articular membranes and fascial aponeurosis. The tumors comprise up to 5-10% of all soft tissue sarcomas and are most common in young adults, occurring in second to fourth decades of life.

More than 85% of synovial sarcomas arise in the extremities, mainly in the lower limbs around the knee. Though they can arise in joint cavities, they may also arise anywhere unassociated with a joint cavity such as head and neck, lower back, abdominal wall, genitourinary tract, thoracic wall and intrathoracic and other much rarer sites. ^[2] Thoracic synovial sarcoma arises often in the chest wall and occasionally in the pleura and lungs. But the numbers of documented primary mediastinal synovial sarcoma is less.

The differential diagnosis of mediastinal synovial sarcomas include other neoplasms of the mediastinum such as sarcomatous mesothelioma, localized fibrous tumors, fibrosarcoma, smooth muscle tumors, spindle cell sarcoma, pleuro pulmonary blastoma and thymoma. ^[1],[5]

Gross specimens are usually well-circumscribed, pink, fleshy mass with a heterogeneous appearance and may display solid, hemorrhagic or cystic components on section. Calcification foci are occasionally found.

Histolgically, classical synovial sarcoma is a mixture of epithelial and spindle cell components exhibiting a biphasic pattern. ^[2],[3],[5] If this tumor shows only one cell type, it can be classified as monophasic spindle cell type or monophasic epithelial cell type synovial sarcoma. Another histological subtype of synovial sarcoma is a poorly differentiated form. Jemstrom defined synovial sarcoma as a biphasic tumor that is histologically composed of two sharply contrasted types of tissues: one type reproduces features of synovial structure, the other type consists of fibromatous element. Therefore, biphasic synovial sarcoma can be easily diagnosed by characteristic histopathologic findings. ^[3],[4] The cytogenetic hallmark of synovial sarcoma is the translocation (x;18) (p 11-q 11) which is found in near 90% of all synovial sarcoma subtypes. ^[2] This chromosomal study is helpful particularly in differentiating between monophasic fibrous types and poorly differentiated forms of synovial sarcoma from other types of spindle cell tumors. Immunohistochemistry is essential to differentiate between monophasic synovial sarcoma from other spindle cell tumors in the absence of molecular tests for diagnosis.

Complete surgical excision of the tumor mass with good margin is the preferred treatment which is often not possible due to the proximity of tumor to large joints and other vital structures. In these situations, conservative surgery and adjuvant radiotherapy is the favored treatment. ^[2] The synovial sarcoma is thought to be generally chemosensitive though this is not translated into survival benefit. But two non-randomized studies suggested that high dose ifosfamide, cisplatin and doxorubicin based chemotherapy may increase disease free and overall survival rates. ^{[6],[7],[8],[9],[10]} Postoperative radiotherapy for synovial sarcoma has not been found to increase survival rate although it is found to improve local control rates, more so when margins of resection were not free of tumor. ^[3],[10]

The reported 5-, 10- and 15-year survival rates with conservative surgery and adjuvant radiotherapy are 76, 63 and 57%, respectively. ^[2] The clinical and histological features signifying good prognosis in synovial sarcoma are i) younger age (<15 years), ii) tumor size < 5 cm, iii) distal extremity location, iv) low tumor stage, and v) the biphasic type. An extensively calcified synovial sarcoma appears to have a more indolent course and better prognosis, while the poorly differentiated tumors have a poor outcome. ^[2] Some investigators did not recognize histologic subtypes and tumor site to be of any prognostic significance. They accepted only primary tumor size, margin of resection and mean mitotic activity as the prognostic factors for survival in synovial sarcoma. Mean mitotic activity of ≤10 per 10 hpf is reported to confer a 10-year cancer-specific survival rate of 46%, compared with a rate of 14% when the mean mitotic activity is greater than 10 per 10 hpf. ^[7] As most of the synovial sarcomas of the mediastinum are large at diagnosis and tend to recur, prognosis of synovial sarcoma of the mediastinum is usually poorer than that of synovial sarcomas of the extremities. ^[1]

Acknowledgment

The authors acknowledge the cooperation of patient′s father for supplying the reports, etc., for our work.

References

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