Solution: Ganglioneuromas is a benign tumor that arises from the neural crest cells of the central nervous system. Ganglioneuromas can arise anywhere there is sympathetic nervous tissue, but the most common locations are the adrenal gland, paraspinal retroperitoneum, posterior mediastinum, head, and neck. The malignant variant of this tumor (ganglioneuroblastoma) has essentially identical radiographic features, so biopsy and/or excision is required. The prognosis for these patients is favorable and a reasonable differential diagnosis would include other neural tumors, lymphangioma, hemangioma, and a retroperitoneal sarcoma.