Synovial sarcoma of the pharynx causing airway obstruction

A 29-year-old man presented to the emergency department with stridor and a background of progressive globus sensation, loud snoring and worsening dysphagia over 2 years. He had not suffered weight loss, and past medical history was otherwise unremarkable.

Flexible endoscopy examination revealed a well circumscribed, encapsulated tumour arising from the left lower lateral wall of the oropharynx and hypopharynx, and from the left arytenoid on its posterior aspect (Box 1). Computed tomography (CT) scanning revealed a 3 × 4.1 cm soft tissue mass arising from the left pharyngeal wall just inferior to the tonsillar fossa (Box 2).

Endoscopic laser resection (microlaryngoscopy) was carried out with several scopes, including a bivalved speculum and a Boyle–Davis gag to gain full exposure. The capsule was broken at its deep aspect; however, macroscopic clearance was achieved with dissection down to healthy muscle. The patient made an uneventful recovery and was discharged on Day 3.

Histopathological analysis revealed a well circumscribed tumour that measured 8 × 4 × 3 cm and was composed of relatively uniform spindle cells showing frequent mitotic activity. The tumour showed focal necrosis and focal calcification. The posterior surface was raw, suggesting incomplete margins. The cells stained positively for vimentin and CD99, and occasional cells stained positively for cytokeratin AE1/AE3 and epithelial membrane antigen (EMA). Fluorescent in-situ hybridisation (FISH) identified an extra copy of the 5′SS18 signal, suggesting the presence of an unbalanced translocation of the SS18 gene at the 18q11 region.

Based on the histological features and FISH results, a diagnosis of monophasic synovial sarcoma was made. Repeat microlaryngoscopy was performed and biopsies of the tumour bed were taken, and histopathological analysis revealed no evidence of residual tumour.

Positron emission tomography (PET) and CT staging scans revealed no evidence of regional or metastatic disease. Postoperative radiotherapy was administered to the surgical bed, delivering 60 Gy in 30 fractions over 6 weeks, with bilateral prophylactic nodal irradiation to 50 Gy. After discussion at the multidisciplinary clinic, the patient was administered four cycles of doxorubicin and ifosfamide chemotherapy. Twelve months after the initial diagnosis, there was no evidence of recurrence on endoscopy or PET scan.

Synovial sarcomas are high-grade soft tissue sarcomas that are thought to arise from pluripotential mesenchymal stem cells.1,2 They account for 10% of all soft tissue sarcomas, and less than 10% occur in the head and neck region.2,3 Since the first case of head and neck synovial sarcoma was described in 1954, there have been fewer than 200 cases reported in the world literature.4 Published cases of synovial sarcoma of the pharynx are rare,5-9 and to our knowledge, this is the first reported case in Australia.

There is a male predominance, with a male-to-female ratio of 3 : 2, and although synovial sarcomas can occur at any age, they are most commonly found in patients aged between 25 and 35 years.5,9,10 The neck is the most commonly reported site for primary synovial sarcoma within the head and neck, followed by the upper aerodigestive tract.4 The most typical presentation is a painless mass;2 however, pain, odynophagia, otalgia, bleeding and, in rare cases, pulmonary metastases have also been described.

Our patient presented with non-specific upper aerodigestive symptoms, which highlights the importance of a thorough clinical examination. Case reports of pharyngeal synovial sarcomas have found that most patients present within 3 months of the onset of symptoms.5-7 This is in contrast with our patient, who presented after years of loud snoring, progressive globus sensation and eventually stridor. This resulted in a very large tumour almost completely occluding the airway.

There are two types of synovial sarcoma, monophasic and biphasic.11 Two-thirds are biphasic, comprising a mixture of elongated basophilic spindle cells and glandular structures made of columnar epithelial cells. Monophasic forms are composed solely of spindle cells or, very rarely, epithelial cells. Monophasic forms are easier to misdiagnose as fibrosarcomas or malignant peripheral nerve sheath tumours, and immunohistochemistry that shows positive reactions for keratin and EMA and FISH can help differentiate these from other sarcomas.1,11

Work-up should include PET and CT scanning of the head, neck and chest to determine the extent of local disease and to search for metastases. The treatment of choice is complete surgical excision with clear margins and adjuvant radiotherapy.4,12-14 For soft tissue sarcomas in general, clear margins have been associated with reduced recurrence and improved survival.12,14 The issue of margin status is particularly important for pharyngeal disease, where attaining wide margins is technically more difficult, and postoperative function for speech and swallowing are important considerations.

Postoperative radiotherapy is increasingly recommended as it is associated with reduced local recurrence;4,13,14 however, a survival advantage is yet to be demonstrated. Treatment of the cervical lymph nodes in patients with nodal disease should comprise therapeutic lymph node dissection. There have been no studies on the roles of elective lymph node dissection and prophylactic regional radiotherapy in node-negative patients, and this is an area for future research.

The role of neoadjuvant or adjuvant chemotherapy for synovial sarcoma is inconclusive. In a meta-analysis of 14 randomised controlled trials,15 doxorubicin-based chemotherapy was associated with improved recurrence-free survival but not overall survival. A more recent study on ifosfamide-based chemotherapy for synovial sarcomas of the extremities showed an improvement in disease-specific survival.16 As always, the benefits of chemotherapy need to be weighed against the potential significant side effects.

Synovial sarcoma is an aggressive disease with a 5-year survival rate of less than 75%.17 There are conflicting conclusions regarding survival among patients with head and neck disease, with some authors reporting a better prognosis for synovial sarcomas of the head and neck compared with the extremities,18 and others reporting a worse prognosis.19 Favourable prognostic indicators include younger age (< 20 years), monophasic subtype, wide excision and, most significantly, smaller tumour size (< 5 cm).3,4

Disease recurrence is a significant problem, with up to 45% of patients with head and neck synovial sarcoma developing a local recurrence and 33% developing distant metastatic disease.4 Further, recurrences occur late, with a mean time to local recurrence of 3.6 years and a mean time to distant recurrence of 5.7 years reported for whole-body synovial sarcoma.17 This highlights the importance of long-term follow-up for these usually younger patients. All patients should initially undergo monthly review, with thorough clinical examination including nasoendoscopy of the pharynx. Where resources permit, patients should also be offered follow-up PET scanning, as this is a sensitive test for detecting recurrent disease.

This case represents a rare example of a monophasic synovial sarcoma of the pharynx. Diagnosis and treatment of this disease is difficult, and recurrence is common and occurs late. Prospective studies are required to further elucidate the roles of adjuvant and neoadjuvant radiation treatment and chemotherapy.

1 Endoscopic view of the oropharynx and piriform region

There is severe narrowing of the airway at the level of the epiglottis.

2 Sagittal computed tomography image

The synovial sarcoma almost completely occludes the laryngeal inlet.