Background and Utility: Currently, immunocytochemical markers for glial tumors (such as Glial Fibrillary Acidic Protein) are used to help grade tumors and indicate the dominant cell type in the tumor. However, such markers are poor indicators of tumor growth potential and response to therapy. These markers can be used to classify tumors into general sunsets, but they yield little information about outcome and potential growth rates for specific tumors. The immunocytochemical marker in this invention is thought to label the cytoplasm of cells in areas where there is ongoing cell division or cells that have the potential to divide; the number of cells which are immunopositive within a tumor may be used to predict how fast a tumor is growing or will grow. In addition, the pattern of immunoreactivity may eventually be used to determine if a particular tumor will respond to therapy. This method will provide a useful diagnostic and prognostic tool for oncologists.