Epidemiology:
• Ganglioneuroma is a rare benign differentiated ganglionic tumor that contains no immature neuroblastic elements.
• Most ganglioneuromas are diagnosed in patients older than 10 years and are most often located in the posterior mediastinum followed by the retroperitoneum
• Can be found at other sites, including the skin, retropharynx or parapharynx, paratesticular region and in the gastrointestinal tract where has been reported in association with several inherited diseases (Cowden syndrome, tuberous sclerosis, and juvenile polyposis)
• Ganglioneuromatous polyposis has been described in patients with type 1 neurofibromatosis and multiple endocrine neoplasia type 2b (MEN-2b).
Clinical presentation:
• Present as large masses in the retroperitoneum or mediastinum and most patients have normal levels of urinary catecholamine metabolites
• Clinically, patients may present with sweating, hypertension, virilization, and diarrhea (due to the presence of vasoactive intestinal peptide, which can be localized to the cytoplasm of the ganglion cells).

Histopathology:
• Grossly, usually is a well-circumscribed tumor with a fibrous capsule. On a cut section, it is gray to yellow and sometimes displays a whorled pattern.
• Histologically, it has a uniform appearance with a background consisting of Schwann cells that crisscross each other with scattered mature ganglion cells which can be present in isolated fashion, or more commonly in small clusters or nests.
• Ganglion cells cytoplasm is typically bright pink and contains one to three nuclei, which may exhibit a mild to moderate degree of atypia. Pigment is sometimes present in the ganglion cells and is believed to represent catecholamine products that undergo auto-oxidation to a melanin-like substance (neuromelanin).
• Immunohistochemistry: Schwann cells are positive for S100 and the ganglion cells are positive for neuronal markers (Synaptophysin, chromogranin, neurofilament protein and Neuron specific Enolase)
 

Prognosis:
• Ganglioneuromas are benign tumors.
• If a metastatic focus of ganglioneuroma is encountered in a lymph node adjacent to the main tumor mass or at a more distant site, then these lesions represent neuroblastomas in which the metastasis of the primary tumor underwent maturation.
• Rarely ganglioneuromas undergo malignant transformation, including de novo ganglioneuromas as well as those derived from maturation in a neuroblastoma.
• Most commonly, the malignant component resembles a malignant peripheral nerve sheath tumor (MPNST).