Synovial Sarcoma of the Parapharyngeal Space

Parapharyngeal space tumors account for less than 1% of all head and neck neoplasms. ¹ Most are benign, and they are usually of salivary gland or neurogenic origin. ¹ Synovial sarcomas are mesenchymal spindle cell tumors that exhibit variable epithelial differentiation.^2–5 Although they typically occur in the extremities of young adults, approximately 3 to 5% arise in the head and neck region, most commonly in the hypo-pharynx.^1,2,4,5 Parapharyngeal space synovial sarcoma is a rare variant.^1,2

We describe the case of a 17-year-old boy who presented with a sore throat and a feeling of a lump in his throat. A diagnosis of tonsillitis was made, and the patient was prescribed a course of oral antibiotics. A few weeks later, he presented to the emergency department again with a persistent sore throat, dysphonia, worsening snoring, and a globus sensation. There was no dysphagia, airway compromise, or systemic abnormality. He reported an intentional weight loss of 12 kg. His medical history included asthma, and his family history included lymphoma in a second-degree relative.

Examination revealed the presence of a large, smooth swelling in the left tonsil and jugulodigastric lymph nodes bilaterally. Neither tonsil was inflamed, and no parotid lesion was palpable. Findings on flexible nasopharyngolaryngoscopy were unremarkable. Magnetic resonance imaging (MRI) demonstrated enlarged palatine tonsils bilaterally and a large encapsulated mass arising lateral to the left tonsil (figure 1). Bilateral neck level II and III lymph nodes as well as adenoid hypertrophy were also noted. These findings were reported as suspicious for lymphoma.

Figure 1.

A: Axial Tl-weighted MRI shows the parapharyngeal mass mediatizing the left tonsil. B: Axial T2-weighted slice shows the enhancing capsular wall with no infiltration of adjacent soft-tissue planes. C: Coronal T2-weighted section demonstrates the large left-sided mass and the bilateralcervicallymphadenopathy. D: Sagittal image shows additional adenoid hypertrophy.

The patient underwent an urgent transoral excision biopsy of the left parapharyngeal space mass and a bilateral tonsillectomy (figure 2). Intraoperatively, the mass was noted to be soft, friable, and well encapsulated, and it extended into the parapharyngeal space. Histology of the mass and the left tonsil revealed epithelioid and sarcomatoid elements consistent with a biphasic tumor and a diagnosis of synovial sarcoma (figure 3).

Figure 2.

A: Preoperative image shows the medialization of the left tonsil and the large left parapharyngeal mass. B: The soft, friable mass is dissected out. C: Image shows the left tonsil with the parapharyngeal mass (left) next to the normal right tonsil (right). D: The surgical field is seen postoperatively.

Figure 3.

Histology of the parapharyngeal space lesion reveals the biphasic pattern, with epithelioid (black arrow) and sarcomatoid (red arrow) elements.

A review of the case by the multidisciplinary sarcoma head and neck team confirmed locoregional control of the tumor and no distant metastasis. The team recommended adjuvant doxorubicin/ifosfamide chemotherapy (6 cycles) and radiotherapy (60 Gy in 30 fractions). At 11 months of follow-up, the patient was disease-free.

Synovial sarcomas are high-grade soft-tissue tumors that show a predilection for males (male-to-female ratio: 3 to 2); they typically occur in the third decade of life.^3–5 There is often a delay in presentation because of the nonspecific nature of the signs and symptoms.^3,6–8

Histopathologically, synovial sarcomas manifest in two classic forms: biphasic and monophasic. When a biphasic (epithelial and sarcomatoid) pattern is observed, a definitive diagnosis of synovial sarcoma may be possible. Conversely, the monophasic pattern, which is more common, is difficult to diagnose on histology because it can be confused with other mesenchymal or epithelioid neoplasms.^1,9 A definitive diagnosis requires detection of a specific translocation between chromosomes X and 18.^1,8

Because of a paucity of cases and prospective studies, management of patients with synovial sarcoma is not standardized. Combined-modality therapy with wide surgical resection and postoperative radiotherapy has been reported to result in a better prognosis.^3,4,8,9 Treatment of cervical nodal disease, which is found in 10 to 20% of cases, should consist of neck dissection; no research data are available for node-negative patients.^3,8 The role of chemotherapy remains controversial.^3,4,10,11

Patients with synovial sarcoma have a generally poor prognosis (5-year survival: 40 to 75%), particularly in cases of positive excision margins.^3,4 Disease recurrence is a significant problem, with as many as 50% of patients developing a local recurrence and 33% developing a distant metastasis.^1,3,4,9,11 Therefore, long-term follow-up is necessary.^3–5,7,9,11