Neuroblastoma.

Neuroblastoma is a malignant tumor of neural crest origin that may arise anywhere along the sympathetic ganglia or within the adrenal medulla. The median age of diagnosis is 2 years; however occurrence is skewed toward younger children, with nearly 35% of cases occurring under 1 year of age and the remainder under 10 years of age. Seventy-five percent of neuroblastomas originate within the abdomen or pelvis, and half of these occur within the adrenal medulla, whereas 20% originate within the posterior mediastinum and 5% within the neck.