Neuroblastoma: biology and staging.

Neuroblastoma is the most common extracranial tumor of childhood, with about 650 new cases each year in the United States. The clinical course of neuroblastoma is variable and depends on age at diagnosis, staging, histology, and specific genetic abnormalities, such as MYCN oncogene amplification or aberrations of chromosome 1p or 11q. A subset of tumors will undergo spontaneous regression, whereas others progress despite aggressive therapy. The varied clinical behavior reflects genetic heterogeneity, with many possible gene candidates identified in studies using comparative genetic hybridization arrays, RNA expression microarrays, and genome-wide association studies. Recent studies implicated the anaplastic lymphoma kinase gene in the tumorigenesis of many familial and some sporadic cases of neuroblastoma. The International Neuroblastoma Risk Group developed a new staging and risk classification, with recommendations for analysis of biological markers in neuroblastoma. This review discusses the biology of these tumors, current and new risk classification, and staging recommendations, with a brief outline of preferred treatment strategies.