Mediastinal schwannoma diagnosed by endoscopic ultrasonography-guided fine needle aspiration cytology.

Schwannoma is the most common neurogenic tumor that is derived from the peripheral nerve sheath. There are no specific serologic markers or characteristic imaging abnormalities associated with schwannoma. Tissue diagnosis and immunohistochemistry are required to diagnose this lesion. We describe a 65-year-old male with a finding of three mass lesions in the superior and middle mediastinum on computed tomography of the chest. The largest lesion measured 4.6 × 5 cm. The patient subsequently underwent endoscopic ultrasonography-guided fine needle aspiration (EUS-FNA) of the lesion and cytology was consistent with spindle cell neoplasm. Immunohistochemical staining of the cytologic specimen was positive for S-100 and negative for pan-cytokeratin, CD34, CD117, calcitonin, smooth muscle actin and desmin. These findings were consistent with schwannoma. This is the second reported case of a mediastinal schwannoma diagnosed by EUS-FNA.