The relationship between Ki-67 labeling and mitotic index in gliomas and meningiomas: demonstration of the variability of the intermitotic cycle time.

The monoclonal antibody (mAb) Ki-67 is a marker for the growth fraction (GF) of tumor cells. The exact relationship between the Ki-67 labeling index (LI) and the conventional diagnostic criterion of the proliferative activity of brain tumors, the mitotic index (MI), is unknown except for some general references. On serial frozen sections Ki-67 LI and MI were determined in nearly identical areas of 32 glioblastomas, 20 grade III astrocytomas, 21 grade II astrocytomas and 20 selected cases of meningioma. The data not only clearly showed different median values of LI and MI for the various malignancy grades, but also similar regression coefficients for each glioma type. A non-linear relationship between the two indices was found for all glioma cases with high significance and high correlation coefficient; (LI) = 5.6 (MI)0.59. This results from differing intermitotic cycle times, the variability of which can be estimated from the data given.