A review of neuroblastoma image-defined risk factors on magnetic resonance imaging.

Neuroblastoma is the most common extracranial solid malignancy in children. Historically, neuroblastoma has been staged using the International Neuroblastoma Staging System (INSS), which relies on surgical staging. This is problematic because surgical resection can vary among surgeons and tumors and occurs at interval times from diagnosis. In 2009 the International Neuroblastoma Risk Group (INRG) created a new staging system that relies on preoperative imaging for staging. The INRG staging system consists of 20 image-defined risk factors (IDRF) across multiple organ systems, which help predict surgical outcomes/adequacy of resection and can be combined with clinical data to provide up-front risk stratification. The purpose of this review is to describe both the INSS and INRG staging systems and their limitations and to illustrate the definitions and IDRFs that comprise the INRG staging system.