Increased proliferative activity due to necroses induced by pre-operative embolization in benign meningiomas

The proliferative behaviour of 35 benign intracranial meningiomas was inves tigated which were embolized for devascularization 3 to 268 hours prior to surgical exstirpation. The nuclear proliferation antigen Ki-67 was visualiz ed by means of the monoclonal antibody MIB1 on formalin fixed and paraffin embedded tissue. Tumor cells and inflammatory reactions were recognized by means of conventional staining procedures and by immunohistochemical detect ion of HAM56, LCA, HLA-DR, CD15-epitope and vimentin. Extravasation and pro liferation of granulocytes, macrophages, lymphocytes and the degree of expr ession of MHCII antigens was estimated according to a 7-point ordinal scale . Confirming preliminary observations of others the proliferation index wit hin the perinecrotic tumor rim (PIperinec) exceeded that of intact tissue h ighly significantly. PIperinec peaked at the third to fourth day after embo lization and kept this level until the seventh day. The time course of PIpe rinec was paralleled by that of macrophages, whereas - expectedly - granulo cytes occured earlier and lymphocytes and HLA-D R-positivity somewhat later . The timely relationships suggested that the perinecrotic increase in tumo r cell proliferation was mainly due to macrophage-born mitogens. Perinecrot ic proliferative activity in embolized meningiomas does not reflect genuine tumor proliferation and should not be used for assessment of the presence or degree of malignancy in a given tumor.