Volume 3, Issue 3 , Pages 105-108, September 2008
Pediatric synovial sarcoma of the right masseter muscle: A case report
Article Outline
Summary
Synovial sarcoma is a rare malignant non-rhabdomyosarcomatous soft-tissue sarcoma in children and adolescents. Only 4% of synovial sarcoma cases develop in the head and neck. Herein, we described a 10-year-old girl with synovial sarcoma of her right masseter muscle. The diagnosis of synovial sarcoma was confirmed by the existence of SYT-SSX fusion gene transcripts, and she was treated with neoadjuvant and adjuvant chemotherapy, surgical resection and postoperative radiotherapy, though standard treatment for synovial sarcoma is complete surgical resection. She remains free of disease 12 months after treatment, and her right masseter muscle has been normal cosmetically and functionally.
Keywords: Synovial sarcoma, Neoadjuvant chemotherapy, Treatment, Diagnosis, SYT-SSX fusion gene
1. Introduction
Synovial sarcoma is a rare malignant non-rhabdomyosarcomatous soft-tissue sarcoma in children and adolescents. Typically, this sarcoma occurs in the extremities of adults in their fourth decade of life, but one half of the reported cases were children and/or adolescents. This sarcoma does not originate from the synovial membrane but rather from primitive mesenchymal cells, and has been classically described as occurring in the soft tissues of the extremities, especially near large joints, but it can occur anywhere in the body in locations distant from joint spaces [1]. In addition, this sarcoma usually presents as a slow-growing mass that may cause symptoms related to compression or infiltration of surrounding structures [2].
Histologically, this sarcoma is characterized by the presence of epithelial and spindle cells, probably derived from a primitive mesenchymal precursor, and by a pattern of different histological subtypes: (a) the biphasic type with distinctive spindle and epithelial cell components, (b) the monophasic fibrous type, (c) the monophasic epithelial type, and (d) the poorly differentiated type [3], [4].
Herein, we described a 10-year-old girl with synovial sarcoma of the monophasic fibrous type in the lateral aspect of her right masseter muscle, which was detected by molecular genetic analysis based on reverse transcription-polymerase chain reaction (RT-PCR) of SYT-SSX fusion transcripts. She was treated with multimodality therapy including neoadjuvant and adjuvant chemotherapy, surgical resection and postoperative radiotherapy, and remains free of disease 12 months after treatment.
2. Case report
A 10-year-old girl was referred to us with a tumor in her right masseter muscle. She had no history of local trauma or systemic disease. The dolor compressionis in the right masseter muscle had first been noted 2 years previously, however, no mass had been detected. She was observed with no specific treatment. A swelling was later found, gradually increased and she was referred to a neighboring hospital. The maximum diameter of the mass measured about 30
mm, and contrast-enhanced computed tomography (CT) showed a mass with a dimension of 24mm×14mm in the right masseter muscle (Fig. 1A). She was then referred to our hospital for multimodality therapy. On referral to us, she exhibited a tumor with tenderness, hard on palpation, in the right masseter muscle. The lesion was hyperintense in T2-weighted magnetic resonance imaging (MRI). Thallium scanning revealed pooling around it, but with no metastatic signs. Prior to surgery, a biopsy was performed with intraoral approach for diagnosis. Histological examination showed a monophasic fibrous sarcoma containing high-grade spindle cells (Fig. 2). Immunohistochemical examination showed the spindle cells to be positive for MIC2 and bcl-2, but negative for vimentin, epithelial membrane antigen, cytokeratin, desmin and alpha smooth muscle actin. We diagnosed her as having extraskeletal Ewing's sarcoma or synovial sarcoma. Then, molecular analysis was successfully performed by RT-PCR examination, using RNA extracted from frozen materials and archival paraffin-embedded specimens, and was confirmed in the presence of SYT-SSX fusion gene transcripts (date not shown). The result of the PCR analysis indicated that she had synovial sarcoma. Initially, we used modified Ewing's sarcoma regimen as the protocol for her. The initial courses of chemotherapy consisted of vincristine (2mg/m2) for 1 day weekly for weeks 1–3, doxorubicin (40mg/m2) daily for 2 days, and cyclophosphamide (2200mg/m2) for 1 day followed by mesna, given to prevent hemorrhagic cystitis caused by cyclophosphamide. The next courses consisted of ifosfamide (2800mg/m2) daily for 5 consecutive days, given with mesna, and etoposide (120mg/m2) daily for the same 5 days. After the same chemotherapy of vincristine, doxorubicin and cyclophosphamide as the third course, the maximum diameter of the mass reduced to 15mm, followed by contrast-enhanced CT (Fig. 1B). Then definitive surgical resection procedure was performed through a parotid-type and S-shaped incision around the angle of the mandible. The marginal mandibular branch, buccal branch and zygomatic branch of the facial nerve were identified and dissected with surrounding connective tissues, and were gently retracted with rubber bands. The tumor was removed en block with a surrounding margin of normal muscle and a periosteum of the mandible (Fig. 3). Postoperatively, a total dose of 50Gy (1.8Gy per fraction per day) was irradiated for a total of 25 days (five times a week) with cyclophosphamide (600mg/m2) and actinomycin D (600μg/m2) weekly for 5 weeks. Irradiation was performed on the region of the right masseter muscle. Subsequently, she received the same multiagent regimen containing vincristine, doxorubicin and cyclophosphamide or ifosfamide and etoposide (Fig. 4).
Fig. 1.
(A) Contrast-enhanced computed tomography (CT) showed a hyperdence tumor in the right masseter muscle (arrow). (B) It after neoadjuvant chemotherapy showed a decrease in hyperdence lesion at the same site (arrow).
Fig. 2.
Histological examination showed spindle cells. A diagnosis of monophasic synovial sarcoma was made. (Hematoxylin and eosin stain, 200×.)
Fig. 3.
Intraoperative photograph showed that the tumor of the right masseter muscle was completely resected.
Fig. 4.
Passage of treatment with multimodality therapy including neoadjuvant and adjuvant chemotherapy, surgical resection and postoperative radiotherapy.
One year after treatment, she was followed up by MRI and remains free of disease. The right jaw joint looked very good, and the function was normal in terms of range of motion and activity.
3. Discussion
Synovial sarcoma is a rare, but one of the most common malignant non-rhabdomyosarcomatous soft-tissue sarcoma types. The incidence rate of synovial sarcoma is approximately 8% of all soft tissue sarcoma cases. Although 85% of synovial sarcoma arises in the extremities, sites in the head and neck, trunk, abdomen–pelvis, mediastinum and lung can rarely be involved. Approximately, 3.7% of patients with synovial sarcoma of all ages had it occurring in the head and neck [5]. In this report, we presented a rare case of synovial sarcoma occurring in the lateral aspect of the right masseter muscle that was successfully treated with multimodality therapy including neoadjuvant chemotherapy.
The reported 5-year progression-free survival and overall survival rates of children younger than 17 years old with synovial sarcoma were 66.3–75.6% and 78.5–87.7%, respectively [3], [5], [6]. The most important and accurate prognostic factors in synovial sarcoma are the extent of tumor resection, and the presence of metastatic disease, the most common site of which is the lung and regional lymph node [6]. The other prognostic factors associated with synovial sarcoma are conflicting. Previously reported favorable prognostic factors include age below 20–25 years, tumor size smaller than 5cm, distal extremity location, and biphasic histological type. However, some studies have shown that age, location of tumor, and histology type is not significantly associated with prognosis [7]. A recent report of multivariate analyses examined the following parameters for their potential prognostic value: age at diagnosis, sex, tumor site, size, histology, mitotic count, necrosis, histological grade, stage, surgical margin status, and fusion type. It showed that the presence of poorly differentiated areas was the strongest prognostic factor associated with local recurrence, metastases, and tumor-related death [7], [8].
In molecular analysis for diagnosis, synovial sarcoma is characterized by the translocation t (X; 18)(p11.2; q11.2), resulting in a fusion between the SYT gene on chromosome 18 and SSX1 or SSX2 on the X chromosome, leading to the formation of new chimeric genes SYT-SSX1 or SYT-SSX2. These SYT-SSX fusion transcripts have been able to be detected in more than 90% of the cases by RT-PCR [4]. Therefore, there are considered to be useful diagnostic markers for synovial sarcoma, especially in the case of poorly differentiated tumors or lesions arising at uncommon sites, as in our case.
The most suitable treatment approach for synovial sarcoma is still controversial. Standard treatment is complete surgical resection, but synovial sarcoma is no longer regarded as unresponsive to chemotherapy and irradiation [3]. Pappo et al. revealed that 9 (56%) of 16 patients with advanced-stage synovial sarcoma achieved complete remission or partial remission by neoadjuvant chemotherapy [9]. In our case, we resected the tumor completely after neoadjuvant chemotherapy, because we wanted to prevent surgery from inflicting damage on the beauty and function of the right masseter muscle. This neoadjuvant chemotherapy in our case was thought to induce successful treatment; namely, this patient had a good appearance and function of the right masseter muscle, although treatment of pediatric sarcoma arising in the head and neck is difficult cosmetically and functionally. To the best of our knowledge, it is rare to undergo neoadjuvant chemotherapy in the treatment of synovial sarcoma arising in the head and neck. However, the benefit of neoadjuvant chemotherapy in the treatment of synovial sarcoma needs to be evaluated in further studies.
4. Conclusion
We presented a pediatric case with synovial sarcoma, which was diagnosed by SYT-SSX fusion gene transcripts, and was successfully treated with neoadjuvant and adjuvant chemotherapy, surgical resection and postoperative radiotherapy.
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PII: S1871-4048(07)00094-9
doi:10.1016/j.pedex.2007.12.001
© 2007 Elsevier Ireland Ltd. All rights reserved.
Volume 3, Issue 3 , Pages 105-108, September 2008
