The differential diagnosis of a posterior mediastinal mass includes neurogenic tumors, esophageal tumors, and neuroenteric cysts. Neurogenic tumors are classified as paragangliomas, nerve cell tumors (eg, neuroblastoma and ganglioneuroma), and nerve sheath tumors (eg, schwannoma and neurofibroma). Neuroblastomas and ganglioneuromas are childhood tumors and are often malignant. In contrast, most neurogenic tumors in adults are benign. Neurogenic tumors are rare but comprise 15 to 25% of all primary mediastinal tumors. A schwannoma is the most common thoracic neurogenic tumor in adults. In one of the largest series of patients with thoracic neurogenic tumors over a 50-year period, 37 of the 86 adults (43%) had a schwannoma. Schwannomas are located predominantly in the posterior mediastinum in the paravertebral sulcus, arising from sheaths of spinal nerve roots and thoracic, intercostal or sympathetic nerves and rarely present as an intrapulmonary mass. There have been rare case reports of schwannomas arising from the phrenic nerve or presenting as an endobronchial lesion. Schwannomas are benign, slow-growing, solitary tumors that rarely undergo malignant transformation. Schwannomas are rarely multiple, and recurrence is uncommon. More than 80% of patients with schwannomas are asymptomatic, and the tumor is often detected incidentally. Patients rarely present with chest pain, back pain, or dyspnea, or with symptoms and signs of spinal cord compression if the tumor extends into the spinal canal. There have been rare reports of thoracic, dumbbell-shaped schwannomas presenting in patient's with Horner syndrome.