Biomarkers are small molecules that can be detected in the body fluids of patients; they often correlate with the presence of a cancer. MicroRNAs and proteins are small molecules which have recently been discovered in cells. They are known to be responsible for the normal development of cells and when they are disrupted can contribute to the development of cancer. Many previous studies have been done evaluating the expression of microRNAs and proteins in normal tissues as well as a wide variety of cancers. Recently, microRNAs and proteins from tumor cells have been detected circulating in the blood of patients with cancer. This presents a novel opportunity to use microRNAs and proteins in the blood as an early predictor of cancer as well as a marker of response to therapy. Previous work in our labs have identified miRNAs and proteins in the blood and cerebrospinal fluid (CSF) of pediatric patients with brain tumors. To determine a longitudinal evaluation of the presence of microRNAs and proteins in the blood, cerebrospinal fluid and urine of patients with central nervous system tumors from diagnosis through the course of their treatment. Though the duration of active treatment varies significantly based upon the diagnosis, patients will be followed for up to 24 months after enrollment onto the study).