- This study will review the molecular pathological alterations of archived human CNS tumor specimens at initial presentation and at subsequent relapse. We will request archived brain tumor tissue samples from the NCI CCR Laboratory of Pathology at multiple time points to determine the expression of cellular proteins and surrogate markers involved in growth, proliferation, differentiation, invasion, and survival of brain tumor cells. Such information will be pooled with imaging data (MRI, PET, etc.) to identify potential surrogate markers of disease resistance.