Mediastinal Schwannoma Masquerading as a Cystic Lesion: A Case Report and Review of the Literature

Abstract

Endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) is a safe and minimally invasive diagnostic technique for the analysis of mediastinal lesions. This approach, however, may result in life-threatening mediastinitis. Here we report a rare case of mediastinal schwannoma presenting as a cystic lesion and pose an important question of risk versus benefit of aspiration of cystic lesions. A 39-year-old man developed persistent non-productive cough and dysphasia to solids for several months. A computed tomography (CT) of the chest revealed a large posterior upper mediastinal mass measuring 6.3 x 4.5 x 8.0 cm displacing the esophagus to the right and the trachea anteriorly, with a standardized uptake value (SUV) of 2.8. The patient then had a bronchoscopy, which showed marked extrinsic compression of the mid trachea without endobronchial disease. An esophagoduodenoscopy (EGD) and EUS were performed and were notable for an 8 cm oval, well-demarcated anechoic lesion with both solid and cystic components adjacent to the esophagus. FNA was intentionally not performed due to the risk of mediastinitis. The patient had a subsequent magnetic resonance imaging (MRI) of the chest showing the 9.3 x 4.1 x 6.0 cm midline retrotracheal superior mediastinal mass. He ultimately underwent posterolateral thoracotomy with excision of the lesion. A frozen section was consistent with a neurogenic tumor. Final pathology revealed a schwannoma. Diagnosis of mediastinal masses poses a significant challenge. The differential diagnosis for a posterior mediastinal mass alone includes neurogenic tumor, neuroblastic tumor, non-neurogenic tumor, paraspinal abscess, hernia, lymphadenopathy or lymphoma, foreget duplication cysts, and thoracic meningocele. EUS-FNA is a minimally invasive and a safe procedure with a complication rate (i.e. infection, bleeding, acute pancreatitis) of approximately 1%. This rate, however, increases when the lesion contains a cystic component rather than a purely solid lesion. Several case reports have described cystic infection and mediastinitis despite accepted techniques including prophylactic antibiotics. Schwannomas generally appear as solid lesions when imaged by either CT or MRI. In 23-30% of cases, this subtype of neurofibromas may be cystic and performing a FNA may result in serious consequences. More data are needed to accurately provide the risks and benefits of EUS-FNA of mediastinal cystic lesions and to validate the use of prophylactic antibiotics for aspiration of cystic lesions.