Urinary Catecholamine Metabolites: Urinary levels of catecholamine metabolites vanillylmandelic acid (VMA) and homovanillic acid (HVA) are elevated in 90% to 95% of neuroblastomas. These markers are used in the initial diagnosis, to monitor therapeutic response, as well as to detect disease relapse. Tumor Biopsy: Tumor tissue is obtained for diagnosis and to classify the tumor according to the International Neuroblastoma Pathology Classification. In addition, the tissue is evaluated for prognostic markers such as MYCN copy number, DNA index, and loss of heterozygosity at 11q and 1p. Bone Marrow Biopsy: Bone marrow evaluation is a routine part of clinical staging and in monitoring disease activity. All of the information gathered from these tests is used to assign the patient to appropriate risk group for planning treatment according to Children’s Oncology Group protocols. The image shows an undifferentiated neuroblastoma composed of a uniform population of undifferentiated neuroblasts without clearly identifiable neuropil or rosettes. The neuroblasts are arranged in sheets or lobules which are incompletely partitioned off by thin fibrovascular septa.