Cell proliferation and invasion in malignant gliomas

Cell proliferation and invasion were studied in sixty biopsies of malignant gliomas selected to reproduce the spreading modalities identified in ninety autopsy cases of glioblastoma. Cell proliferation was studied by the immunohistochemical demonstration of PCNA and MIB-I and by the calculation of their labeling indexes (LI). The main finding was that cell proliferation and cell invasion are not necessarily associated. The interface between the solid tumor and the adjacent brain was represented either by a gradient of tumor cell density or by a clearcut demarcation of the tumor. In the first case the LI either did not change in the infiltration area in comparison with solid tumor or it was much lower, whereas in the second case there was a ring with a high density of labeled nuclei at the tumor periphery. Perineuronal satellites were usually positive for proliferation markers. Cells accumulated in the outer cortical layers, from a deeply located tumor were almost negative, whereas those originating from subarachnoidal or subpial invasion showed a high LI. High LIs were also found in subarachnoidal and subpial growths, and in a cell population descending into the brain parenchyma around meningeal penetrating vessels. The relationship between cell proliferation and invasion from in vivo studies is not a direct and a simple one.