Intraneural Synovial Sarcoma of the Digital Nerve in a Hand

Synovial sarcoma is a mesenchymal spindle cell tumor with variable epithelial differentiation; it usually occurs in adolescents and young adults. Synovial sarcomas, which account for 5% to 10% of soft-tissue sarcomas, may occur at any site; however, they are believed to arise initially from the synovium1. With the advancement of molecular genetics, synovial sarcomas now can be diagnosed by molecular genetic studies with the identification of the SYT and SSX novel genes2,3. Despite the advancement of diagnostic tools, intraneural synovial sarcomas arising in the peripheral nerves of the upper limb are very rare. To the best of our knowledge, only twenty-seven cases of intraneural synovial sarcomas previously have been reported4-20. Among these, only nine cases have noted the involvement of the peripheral nerves of the upper limb4-6,9,13,15,16,18. This case report describes a twenty-six-year-old man who presented with a painless mass on the volar-radial aspect of the index finger. Eighteen months prior, the patient had undergone excisional biopsy at a different hospital, and the mass had been diagnosed as a schwannoma. When the patient presented to us, we initially believed that the tumor had recurred; however, the final diagnosis, as shown by histology, immunohistochemistry, and molecular genetics, was an intraneural synovial sarcoma. The patient was informed that data concerning the case would be submitted for publication, and he provided consent. A twenty-six-year-old man visited our clinic because of a painless mass that was located on the volar side of the metacarpophalangeal joint of the right index finger. Eighteen months prior, he had visited another hospital because of the same lesion. At that time, magnetic resonance imaging (MRI) had revealed a schwannoma of the radial digital nerve in …