MicroRNAs 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 in normal tissues as well as a wide variety of cancers.

Recently, microRNAs from tumor cells have been detected circulating in the blood of patients with cancer. This presents a novel opportunity to use microRNAs in the blood as an early predictor of cancer as well as a marker of response to therapy. No previous studies have been performed evaluating microRNAs in the blood or cerebrospinal fluid of patients with childhood cancers. We propose a feasibility study to evaluate the presence of microRNAs in the blood and cerebrospinal fluid of patients with central nervous system tumors, leukemia and lymphoma who are currently on chemotherapy and undergoing blood draws, lumbar punctures and/or reservoir taps for routine clinical care. If we're able to identify circulating microRNAs in this population of pediatric patients, we will build upon this data in proposing a future study.

Inclusion Criteria:

• All children who are in treatment for leukemia, lymphoblastic lymphoma and central nervous system tumors
• age: greater than 3 years and less than or equal to 21 years of age
• Patients must be in a phase of their treatment during which routine blood draws, lumbar punctures or CSF sampling from Ommaya reservoirs are required for treatment of their cancers.

Exclusion Criteria:

• Patients who have completed treatment and do not require routine blood draws and/or lumbar punctures
• Patients who are considered too ill to participate as determined by their treating physician
• Patients with a known genetic condition that predisposed them to the development of cancer.

All children who are in treatment for leukemia, lymphoblastic lymphoma and central nervous system tumors