Immunohistochemical Study of Ki-67 Labelling Index in Neoplasms of Central Nervous System

Introduction: The central nervous system tumours show a varied histopathological spectrum. The cell proliferation index may provide an objective method for assessing tumour biology. The Ki-67 is considered to be the most reliable proliferative marker predicting the tumour behaviour of various systemic and intracranial neoplasms. As it reflects tumour proliferating potential, it helps in determining the grade and hence the likelihood of recurrence. This study was carried out considering that very few studies of Ki-67 Labelling Index (LI) is seen in Central Nervous System (CNS) neoplasms collectively. Aim: To study the Ki-67 LI in CNS neoplasms and the association of Ki-67 LI with different parameters like age, sex, World Health Organisation (WHO) grading and histological types. Materials and Methods: The present descriptive analytical study was conducted at Department of Pathology, Mahadevappa Rampure Medical College, Karnataka, India, attached to a tertiary care hospital, Kalaburagi, for a period of five years between 1st Aug 2013 to 31st July 2018 after approval from the Institutional Ethics Committee. The formalin-fixed and paraffin-embedded tissue sections were stained with haematoxylin and eosin. Immunohistochemistry (IHC) was carried out with Ki-67 antibody using standard protocol. The data was analysed using IBM SPSS software version 19.0. The descriptive statistics frequency and percentages were calculated. The morphological grading of CNS tumours was done and the distribution of Ki-67 LI values were analysed. Results: A total of 102 histopathologically diagnosed primary CNS tumours were included in the study. High incidence of CNS neoplasms was seen in 3rd to 4th decade with slight male preponderance. This study included 40 meningioma cases. Mean percentages of Ki-67 LI for grade I and grade II meningiomas were 3.3% and 4%, respectively. The Ki-67 mean value for Astrocytomas grade I was 5.6% and grade II was 8.7%. Grade IV Glioblastoma and Gliosarcoma showed mean value of 18% and 18.8%, respectively. It was observed that LI increased with increase in grade of the tumour. Schwannoma and Dysembryoplastic Neuroepethelial Tumour (DNET) showed Ki-67 LI of 2.9% and 2.6%, respectively. Mean value of Ki-67 LI of other primary CNS neoplasms were as follows: Medulloblastoma 53%, Atypical Teratoid/Rhabdoid Tumour (ATRT) 32%, Haemangiopericytoma 8%, Neurocytoma 4%, Malignant Peripheral Nerve Sheath Tumour (MPNST) 3%, Ganglioglioma 4% and Haemangioblastoma 4%. Conclusion: The Ki-67 LI is the simplest and the most reliable method for evaluating the cell proliferation. It has a great value in designating the exact grade of the tumour when used in combination with histopathological features. It can also be used for planning of adjuvant therapy in primary CNS neoplasms.