ABSTRACT
The classification and grading of primary tumors of the nervous system have been in flux ever since the first system was introduced. The revised World Health Organization (WHO) Classification (Table 1) (1) may prove to be the most widely accepted classification, but, as it remains morphology based, will likely undergo further refinement. Interobserver variability continues to be a problem and the availability of more objective, prognostically meaningful markers would be desirable. This chapter provides an overview of the current classification system and summarizes the main histological and molecular features of nervous system tumors.
