Synovial sarcoma of the suboccipital region of the neck.

A synovial sarcoma (SS) is an uncommon malignant soft-tissue tumor, which in spite of its name does not arise from synovial tissue. It is so named because of its histologic similarity to synovium. An SS originates from mesenchyme, not from synoviocytes and usually manifests as a biphasic tumor with both malignant-epithelial and spindle-cell components. Monophasic epithelial and spindle-cell presentations may cause a diagnostic dilemma. Diagnosis should include immunocytochemistry using cytokeratin and/or epithelial membrane antigen; vimentin further helps to eliminate any histologic confusion. These tumors are most commonly found in the extremities. When located near a joint, invasion occurs only by secondary extension. Rarely are SSs found in the neck, especially in the posterior aspect, as reported here.