Proliferation Potentials of Human Intracranial Neoplasms Assessed with Ki-67 (MIB-1) Labeling Index and Argyrophilic Nucleolar Organizer Regions

To evaluate the accuracy of the Ki-67 labeling index (LI) as an index of brain tumor proliferation, specimens of 303 intracranial neoplasms were examined for tumor proliferation potentials as assessed by MIB-1 (Ki-67 antigen) immunostaining and/or counting the argyrophilic nucleolar organizer regions (Ag-NORs). The Ki-67 LIs were higher in the histologically high grade tumors, i.e., the metastatic carcinomas, malignant lymphomas, glioblastomas, medulloblastomas, anaplastic astrocytomas, anaplastic oligodendrogliomas, anaplastic ependymomas, and anaplastic meningiomas compared to the histologically low grade tumors, i.e., the pilocytic astrocytomas, grade II astrocytomas, oligodendrogliomas, ependymomas, meningiomas other than those of the anaplastic variety, and pituitary adenomas. The number of Ag-NORs was not correlated with the tumor grade, and was inconsistent with the growth potential in some tumors. Moreover, in the consecutive sections of 87 tumors stained for both Ki-67 and Ag-NORs, the number of Ag-NORs did not correlate with the tumor Ki-67 LI in a regression analysis (r = 0.139). The patients with a high grade astrocytoma (anaplastic astrocytoma and glioblastoma) and a tumor Ki-67 LI > 10 had significantly shorter survival periods than those of the patients with a Ki-67 LI < 10 (p = 0.029). Our results thus suggest that Ki-67 is a potential marker of tumor growth activity and that the Ki-67 LI may be of use as an indicator of the prognosis of patients with brain tumor. The number of Ag-NORs may not always reflect the growth potential of some tumors