Cell proliferation and tumors of the central nervous system. Part 1: Evaluation of mitotic activity.

Evaluation of cell proliferation has been long recognized in pathology as a mainstay of diagnosis and important in the prognostication of a variety of neoplasms. Routine light microscopic evaluation of mitotic activity has long served as a reasonable assessment of cell proliferation. Counting mitotic figures has the advantage of being inexpensive and relatively quick. The main objections leveled against utilization of mitosis counts in diagnostic decision making are related to the instability of mitotic figures due to prefixation and fixation issues and problems with interobserver reproducibility of counts. This paper reviews factors that affect the identification of mitotic figures and the determination of mitosis counts. The role mitosis evaluation plays in the evaluation of certain neoplasms of the central nervous system is discussed.