Differentiation between reactive gliosis and astrocytomas by MIB-lIki67 immunostaining

BACKGROUND: Astrocytic tumors are the most common primary tumors of the central nervous system. These tumors have an inherited tendency to progress and recurrence. The histopathological examination and grading do not always identify the subset of these tumors especially when the tumor sample is small or inadequate. This study was undertaken to answer the question whether MIB-I expression could assist in discrimination between low grade and high-grade glioma and gliosis especially when the biopsy sample is small, such as in stereotactic brain biopsy. Methods: This descriptive analytical study was performed on 114 glial and gliotic paraffin-embedded tissues. KI67 immunohistochemistry was also used on paraffin section using the monoclonal antibody MIB-l. The results were analyzed by ANOVA test. Results: Based on light microscopic findings 89 (78.07%) were astrocytomas and 25 (21.9%) were reactive gliosis. The mean Ki67 labeling index (LI) was 25.2% ((PLUS-MINUS)30) for astrocytomas in general and 1.92 ((PLUS-MINUS)1.2) for gliosis. In other words, it was 1.8 ((PLUS-MINUS)I) for grade I, 14.5% ((PLUS-MINUS)4) grade II and 64.5 % (±19.3) for grade IIIIIV astrocytomas. The MIB-l labeling index for astrocytic tumors was significantly higher than that for gliosis (P(LESS THAN)O.OO I) and it increased with increasing tumor grade. However, MIB-I labeling index was the same for pilocytic astrocytoma and gliosis so there was no meaningful difference between grade I astrocytoma and gliosis. CONCLUSIONS: Given the conventional microscopic examination and KI67 (MIB-I) method for grading astrocytomas, MIB-I is more reliable and a complementary method for definitive diagnosis.