One-fifth of all neuroblastomas are diagnosed either antenatally or in the first 3 months of life. Over the past two decades, routine prenatal ultrasound has significantly increased the rate of diagnosis of fetal neuroblastoma. More than 90% of these tumors arise in the adrenal gland, suggesting a link between perinatal tumors and the nodular collections of neuroblasts that are part of normal adrenal development. In fact, there is compelling evidence that the cystic variant of perinatal neuroblastoma is caused by a perturbation of the involution program of these neuroblastic nodules. The vast majority of these cases are localized tumors with favorable biological features, which correlates with a 4-year survival of greater than 95%. The high rate of spontaneous regression of these tumors, coupled with the significant risks of resectional surgery in small neonates, has prompted the development of a prospective clinical trail of expectant observation as primary therapy for infants with small, localized tumors. The ultimate goal of such studies is to define an ultra-low-risk group of neuroblastoma patients who do not require invasive procedures or chemotherapy to achieve an excellent outcome.
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