Neuroblastoma (NB) is the most common extracranial solid cancer in childhood and the most common cancer in infancy, with an incidence of about six hundred fifty cases per year in the U.S. and a hundred cases per year in the UK. Nearly half of neuroblastoma cases occur in children younger than two years. It is a neuroendocrine tumor, arising from any neural crest element of the sympathetic nervous system (SNS). It most frequently originates in one of the adrenal glands, but can also develop in nerve tissues in the neck, chest, abdomen, or pelvis. Neuroblastoma is one of the few human malignancies known to demonstrate spontaneous regression from an undifferentiated state to a completely benign cellular appearance.
It is a disease exhibiting extreme heterogeneity, and is stratified into three risk categories: low, intermediate, and high risk. Low-risk disease is most common in infants and good outcomes are common with observation only or surgery, whereas high-risk disease is difficult to treat successfully even with the most intensive multi-modal therapies available. Esthesioneuroblastoma, also known as olfactory neuroblastoma, is believed to arise from the olfactory epithelium and its classification remains controversial. However, since it is not a sympathetic nervous system malignancy, esthesioneuroblastoma is a distinct clinical entity and is not to be confused with neuroblastoma.