Synovial sarcoma of the head and neck

Clinical History

A 20-year-old man was admitted to hospital because of a growing palpable mass in the right lateral region of the neck, first noticed eight months prior. He referred occasional pain and weight loss. There was no history of trauma, no fever. At physical examination, the mass was hard and elastic.

Imaging Findings

Sonography showed a solid-cystic mass with increased vascularity in the solid portion. Contrast-enhanced axial CT showed a voluminous, well-defined mass. The lesion was heterogeneous with low-attenuation areas and a few intra-tumoral calcifications. The solid mural nodules showed moderate contrast enhancement.
On T1-weighted MR images, the lesion exhibited an intermediate signal intensity.
T2-weighted MR image showed a heterogeneous necrotic mass involving the carotid space, displacing the carotid artery anteriorly, and jugular thrombosis. It produced mass effect on the larynx with mild narrowing of the airway. The left thyroid lobe is displaced cranially.
Contrast-enhanced MR images showed a moderate and heterogeneous enhancement.

Discussion

Synovial sarcoma can occur at all ages but most frequently affects young adults and adolescents. Synovial sarcomas account for 7-10% of all sarcomas and around 6% arise in the head and neck. These tumours do not originate from synovial tissue, but rather from pluripotential mesenchymal cells near or even remote from articular surfaces. In the head and neck, the hypopharynx is the most commonly involved site.
Manifestations of synovial sarcoma vary according to the tumour site. In case of cervical tumour the manifestations include dyspnoea, hoarseness or dysphagia, and palpable mass.
Common imaging findings in this tumour are solid masses on CT or MR images with well-defined smooth margins. Occasionally, the tumour may present cystic or haemorrhagic components and calcifications. Contrast enhancement pattern is variable, but a moderate degree of enhancement is a usual feature [1].
Synovial sarcoma is frequently misclassified as a benign mass because of its smooth margin, cystic components and lack of aggressive infiltration. Schwannoma, neurofibroma with a cystic change and tumour of ectopic minor salivary glands may be considered in the differential diagnosis. Squamous cell carcinoma, although it is the most frequent head and neck tumour, is easily differentiated from synovial sarcomas. The differential diagnosis with other malignant tumours includes sarcomas of the head and neck (most frequently with rhabdomyosarcomas) and Non-Hodgkin's lymphoma.
CT and MR images are useful to define the margins and anatomic relationship.
CT classically displays a multilocular tumour with smooth margins and heterogeneous enhancement after contrast. It is usual to find calcifications, associated with better survival. CT also allows assessment of possible airway compression [2].
MR imaging displays an isointense signal to muscles on T1 weighted sequences, a variable intensity on T2 weighted sequences and heterogeneous enhancement after contrast. Areas of haemorrhage, fluid-fluid levels, and cyst formations are frequent.
The final diagnosis is made with biopsy [3].
The recommended treatment is a wide excision with negative margins, often including surrounding muscle groups. Postoperative radiotherapy is advocated in the head and neck to improve local control rates; adjuvant chemotherapy may prevent or delay the occurrence of distant metastases, although there are insufficient data to support it.
The size of the primary tumour, resection margins, and histological type are the major prognostic factors for survival in the cases of synovial sarcoma described in the literature [4].

Differential Diagnosis List

Final Diagnosis

Synovial sarcoma

URL:	https://www.eurorad.org/case/10417
DOI:	10.1594/EURORAD/CASE.10417
ISSN:	1563-4086