Histopathological Spectrum of Meningiomas with Emphasis on Prognostic Role of Ki67 Labelling Index

Background & Objective: Meningiomas are the most frequently encountered primary non-glial tumors of the central nervous system (CNS). The Ki67 labelling index (Ki67LI) is a proliferation marker that may prove useful in determining the histological grade. This study aims at: 1) Studying the frequency, grade and histomorphological spectrum of meningiomas, 2) Evaluating 20 histological parameters and determining its utility in grading meningiomas and 3) Comparing the Ki67LI in the various subtypes and WHO grades. Methods: The cases of meningiomas diagnosed in our Department from June 2009 to May 2014 were included. The clinical details, grade and 20 histological parameters: mitosis, vesicular nuclei, macronucleoli, nuclear pleomorphism, scattered bizarre nuclei, hypercellularity, sheeting, lymphocytes, small cell change, foam cells, ossification, necrosis, papillary change, lipidization, psammoma bodies, vascularization, brain invasion, dural invasion, bone invasion and other soft tissue invasion were recorded for each case. The average and highest Ki67LI was recorded as percentage and number per high power field. Results: A total of 175 cases of meningioma were included: grade I (145), grade II (30). Atypical histological features like hypercellularity, sheeting, etc. were common in grade II tumors. Increased vascularity, lymphocytes and psammoma bodies were common in grade I tumors. Ki67LI (highest) ranged from 1-6% in grade I and 5-12% in grade II tumors. Conclusion: Among different methods showing mitotic activity, Ki67% (highest) was the most statistically significant LI in differentiating grade I and grade II tumors. The median Ki67% (highest) was 4% for grade I and 7% for grade II tumors.