Clinical, pathological and unusual MRI features of five synovial sarcomas in head and neck

OBJECTIVE: Synovial sarcoma (SS) of the head and neck is an unusual malignancy. This article documents five SSs in this region. METHODS: All the patients underwent MR examinations. Four lesions received surgical ablation; one was treated with radiotherapy before surgery. The clinical, pathological and MRI features were reviewed. RESULTS: Four of all five cases were monophasic fibrous-type SS, and the other one was biphasic type that was the fourth documented SS located in the nasopharynx. The symptoms were varied. All the masses were well defined, mainly homogeneous and solid; three of them arose adjacent to the minor joint. The mass parenchyma showed isointense signal on T(1) weighted imaging similar to that of the skeletal muscle and hyperintense signal on T(2) weighted imaging with remarkable enhancement. Two cases were found with fibrous septum, one with haemorrhage and one with cystic degeneration. Epithelial membrane antigens (EMAs) were all positive. The positive rate of cytokeratin (CK), part pan-CK antibody (AE1/3) and vimentin (Vim) were 50%, 75%, 75%, respectively. CONCLUSION: Well-defined head and neck masses frequently arise adjacent to the minor joint, which are mainly homogeneous and solid, with isointense signal on T(1) weighted MRI and hyperintense signal on T(2) weighted MRI, and remarkable enhancement should evoke the diagnosis of SS. The positive staining of Vim\AE1/3\EMA and CK facilitates the final diagnosis. ADVANCES IN KNOWLEDGE: The article documents the fourth SS involving the nasopharynx; other locations were also uncommon; three of them arose adjacent to the minor joint. The clinical, pathology and uncommon MR features of SS in the head and neck are also documented.