Annals of Case Reports Case Report Primary Synovial Sarcoma of the Mandible: Report of a Case

Synovial sarcomas of the head and neck region are uncommon, accounting less than 10% of all head and neck soft tissue sarcomas. The most frequent sites are hypopharynx and parapharyngeal space. Synovial sarcomas are extremely rare in the oral cavity and may increase the potential for misdiagnosis. Only a few intraoral synovial sarcomas have been well documented. In this report we present a case of a primary synovial sarcoma of the mandible of a 15-year-old male. The histological features are described and diagnostic, prognostic and therapeutic problems are discussed. Special immunohistochemical stains and cytogenetic studies can help in confirming the diagnosis. Therapeutic standards are lacking due to the rarity of synovial sarcomas in the oral cavity. Combined modality therapy of this aggressive tumor better results; however the 5 year survival rate of these patients is poor.


Introduction
Synovial Sarcoma (SS) is a rare and highly malignant soft tissue tumor with a predilection to the lower extremities of adolescents and young adults. More usually the tumor is "Parasynovial" or adjacent to joint capsules, tendon sheaths or bursae, although an increasing number of SSs are found to arise in areas remote from any articular or periarticular structure [1]. Although almost any site can be affected, a distinct region of involvement is the head and neck, especially the hypopharynx, the postpharyngeal region and the parapharyngeal space [1,2]. It was eventually realized that SS did not arise from synovial cells, but was presumed to differentiate from an undefined mesenchymal cell.
SS has been reported only rarely in the oral cavity. There have been reported only few cases of synovial sarcomas of the mandible. The aim of this article is to report one additional case in a 15-year-old male and discuss the related diagnostic, prognostic and therapeutic challenges.

Case Report
A 15-year old male was referred to our department for evaluation and treatment of recurrence of an intraoral biphasic synovial sarcoma of the mandible. There was a painless mass of soft constitution, without ulceration at the right sight of the mandible, extending from the canine to the premolar region. There was no paresthesia of the right inferior alveolar nerve. The patient's medical history was unremarkable. On examination, his general health appeared well.
The patient underwent 7 months earlier in another hospital, a surgery for an intraoral lesion that revealed glandular biphasic synovial sarcoma. He did not receive any postoperative adjuvant therapy. At presentation, MRI control showed a mass of 1.27 X 0.75 cm in the right side of the mandible. In T1 gadolinium contrast  The tumor was widely excised through a marginal mandibulectomy and a simultaneously performed selective neck dissection. Grossly, the specimen contained a 2.0 cm in greatest dimension, fleshy and red-gray mass. The surgical margins of the specimen were negative and in a safe distance of more than 1 cm. There were no cervical metastases. Histologically the tumor contained spindle cells. Some epithelioid cell and no glandular formations were found (Figure 3).

Discussion
Synovial Sarcoma (SS) is a rare, malignant soft tissue tumor of children and adults representing 5.6% to 10% of all soft tissue sarcomas [3]. Almost 60% of the patients are between 15 and 40 years of age. It can occur in almost any part of the body [1,4], with approximately 9% occurring in the head and neck region. The first description of SS was by Pack and Ariel in 1950 [5]. There are only 7 cases affected the mandible reported in the literature (Table  1).  The cell of origin for this tumor is believed to be an uncommitted mesemchymal cell that undergoes synovioblastic differentiation [3,10]. Histological, the following subtypes can be distinguished: a) monophasic SS containing spindle cells, b) biphasic SS, containing both epithelial and spindle cell components, c) a poorly differentiated type of SS (20% of SS) and d) a rare form of monophasic SS, containing only epithelial-like cells [11]. Nearly 90 to 95% of SS demonstrates specific t (x; 18) (p11.2-q11.2) chromosomal translocation that forms the SYT-SSX fusion gene [8]. In some cases, the cytogenetic analysis of the tumor cells can be of great help in clarifying the histogenesis. Histological differential diagnosis varies with the sub-type of synovial sarcoma. It can include low-grade fibrosarcoma, undifferentiated spindle cell carcinoma, malignant schwannomas and carcinosarcomas.
Wide surgical resection and local control should be the primary surgical goal [11]. SS was noted to have increased sensitivity to high-dose ifosfamide-based chemotherapy with encouraging results [12]. SS has been long recognized as a high grade soft tissue sarcoma with a high metastatic propensity. Late distant metastases particularly to the lungs may occur up to 10 years after initial treatment [13]. Tumors greater than 5 cm seem to have a significantly poorer 10-year patient survival (49%) than tumors of 5 cm or less (77%). The 5-cm criterion has been verified as a useful prognostic factor in this disease by several investigators [12]. In conclusion, radical surgical intervention and long-time follow-up are necessary for patients with synovial sarcoma.