Determination and Comparison of Ki-67 Index in Astrocytic Tumours: A Tertiary Care Centre Experience

Abstract

Introduction: The proper management of the astrocytic tumours largely depends on its correct diagnosis. But, smaller size and complicated histomorphology makes it difficult for the histopathologist to conclude the diagnosis. Monoclonal antibody Ki-67 {MIB-1/MIB-1 Labelling Index (LI)} plays a role of diagnostic as well as prognostic marker. It is an important marker, since it helps in deciding malignant potential of the astrocytic tumours where histology alone does not suffice. This study promotes the idea of including Ki-67 in routine practice for astrocytic tumours as it helps in quantifying the growth of the tumour which is of utmost importance in predicting the outcome accurately. Aim: The aim of this study was to determine the mean and ranges of Ki-67/MIB-1 LI in astrocytic tumours and comparing between different grades. Materials and Methods: This was a hospital based cross- sectional study with 50 cases of astrocytoma of varying grades over period of six years, retrospective study period started from 1st April 2009 till 30th November 2012 and prospective study period started from 1st December 2012 till 31st March 2014. Immunolabeling was done using Ki-67/MIB-1 antibody. The mean and ranges of Ki-67 was calculated in astrocytic tumours and its correlation with each World Health Organization (WHO) grade of histological diagnosis and clinical presentations were studied. One-way Analysis of Variance (ANOVA) and unpaired t-test were used for statistical analysis. Results: There were 50 astrocytic tumours, Pilocytic Astrocytoma (PA), grade I-5 (10%) cases; Diffuse Astrocytoma (DA), grade II-8 (16%) cases; Anaplastic Astrocytoma (AA), grade III-10 (20%) cases; and Glioblastoma Multiforme (GBM), grade IV-27 (54%) cases, with mean Ki-67 LI as 2.63%, 2.65%, 18.85% and 30.2%, respectively. The difference in mean Ki-67 LI for low grade astrocytoma and high grade astrocytoma was highly significant statistically (p<0.0001). The most common presentation was seizure, which was seen in 26 (52%) cases. Conclusion: Histological grading with Ki-67 LI can work synergistically to reach the diagnosis, as both are subjected to heterogeneity induced diagnostic accuracy. Ki-67 LI increases with increase in the grade of the astrocytic tumours and hence, its quantification can help histopathologists as well as clinicians to agree on a point, especially in those cases where two differ diagnostically and it effects patients’ prognosis.