Monophasic parapharyngeal synovial sarcoma diagnosed by cytology, immunocytochemistry, and molecular pathology: case report and review of the literature.

Synovial sarcoma (SS) of the head and neck region are rare, accounting for less than 10% of all head and neck soft tissue sarcomas. A limited number of SS have been reported in the parapharyngeal space and these reports have all been based on histological examination of resection material. The diagnosis of monophasic SS on cytology is extremely difficult. We report the first case where a SS was correctly diagnosed on a fine needle aspirate by cytology with the assistance of immunocytochemistry and fluorescence in situ hybridization. We will emphasize the importance of ancillary techniques, such as immunocytochemistry and cytogenetic/molecular pathology, in avoiding diagnostic pitfalls and correctly diagnosing monophasic SS on cytologic material. We will propose an algorithmic approach to accurately diagnose parapharyngeal spindle cell neoplasms with the use of appropriate ancillary studies in conjunction to morphological features.