Ganglioneuroma is a benign neuroectodermal tumor composed of ganglion and Schwann cells. There are no immature neuroblastic elements. The most common sites of involvement are along the distribution of sympathetic nervous system and include posterior mediastinum, retroperitoneum, and adrenal gland. Other sites include skin, pharynx, paratesticular region, and gastrointestinal tract. Gastrointestinal ganglioneuromas may be associated with MEN 2B, neurofibromatosis-1, Cowden syndrome, tuberous sclerosis, and familial adenomatous polyposis. Retroperitoneal and posterior mediastinal tumors occur in young adults. Adrenal ganglioneuromas involve adults in their 4th or 5th decade. Most patients are asymptomatic. Some develop sweating and hypertension (elevated catecholamines), abdominal cramping and diarrhea (vasoactive intestinal peptide) or virilizing symptoms in female patients (testosterone-producing Leydig cells). The tumor is well-circumscribed with a homogenous grayish-white cut surface. It is composed of intersecting bundles of Schwann cells and scattered nests and clusters of ganglion cells in a myxoid or hyalinized stroma. The ganglion cells are not fully mature and lack satellite cells and Nissl bodies. They may be multinucleated and may show mild to moderate atypia. Ganglioneuromas pursue a benign course. They can grow extremely large and encase vessels. Rare cases may undergo sarcomatous transformation to a malignant peripheral nerve sheath tumor. Composite tumors of pheochromocytoma and ganglioneuroma have been reported. Reference: Enzinger & Weiss’s Soft Tissue Tumors, Sixth Edition, 2014; p. 791-792.