Solitary fibrous tumor of the middle ear: Immunoexpression of NAB2-STAT6 fusion gene

Abstract Objective To describe the clinical and pathological findings of a rare case of a solitary fibrous tumor (SFT) arising in the left middle ear, treated with middle ear surgery. Patient A 51-year-old woman presented with a 5-month history of left hearing loss and otalgia. Preoperative otoscopic findings revealed a pulsating blue mass, leading us to the diagnosis of a glomus tympanicum tumor. The tumor was completely resected with mastoidectomy using the facial recess approach. Histopathology showed cells with a low nuclear-to-cytoplasm ratio, having a uniform short spindle-shaped and circular, densely stained nucleus. By immunostaining, the cells were bcl-2 and STAT6-positive. Using a chimeric gene search of the surgically resected specimen, the NAB2-STAT6 fusion gene was detected. The patient was finally diagnosed with SFT. No recurrence was found in the 36-month computed tomography follow-up. Conclusions Extrapleural SFTs have often been reported but no SFT arising in the middle ear have ever been reported in the literature. The SFT of the middle ear had similar clinical manifestations as the glomus tumor in that they are hypervascular neoplastic lesions. Immunoexpression of the NAB2-STAT6 fusion gene were useful for the diagonosis of SFT.