Neovascular basement membrane and its significance in the biological behavior of astrocytic tumors

The correlation between morphological changes of neovasculature in astrocytic tumors and tumor biological behavior, were studied using anti‐collagen type IV, von Willebrand factor and Ki‐67 (MIB‐1). Forty‐four astrocytic tumors were histologically classified into Grade 1 (G1) to 4 (G4), according to the Daumas‐Duport classification. To evaluate quantitative changes of the basement membranes (BM) of neovasculatures, the most significantly altered location was chosen and four morphological changes were used as morphological criteria: dissociation, fusion, glomeruloid change and thickening. Basement membrane grades were determined according to these criteria as encountered on the sections. If none of the criteria was found (such as in vesssels in the normal brain) a BM grade 1 (BM‐1) was given, BM‐2 was used when one of the four criteria was noted, BM‐3 for two, BM‐4 for three, and a score of BM‐5 was assigned if all four morphological changes were noted. All cases of G1 and G2 corresponded to BM‐1 or BM‐2; all cases of G3 corresponded to BM‐3; and all cases of G4 corresponded to BM‐4 or BM‐5. Microscopic angiogenesis grading system (MAGS) scores and endothelial Ki‐67 labeling index (eKi‐67 LI) were also correlated with histopathological grading. Significant differences between eKi‐67 LI and MAGS scores were identified among each BM grade, but not between BM‐2 and BM‐1. It is important for tumor grading and behavior to evaluate the degree of morphological changes of BM in astrocytic tumors, especially fusion and glomeruloid change.