Evaluation of Nuclear Morphometry and Ki-67 Proliferative Marker in Astrocytomas: A Ambispective Study

Introduction: Astrocytomas are the commonest primary Central Nervous System (CNS) tumours. Its diagnosis is based on histopathological criteria defined by the World Health Organisation (WHO) 2016 that grades astrocytoma into four grades. The subjective nature of WHO grading has prompted for more objective methods to evaluate nuclear features. Furthermore, Ki-67, a marker of cellular proliferation is a useful diagnostic tool that also helps in prognostic evaluation and to plan adjuvant therapy in astrocytomas.

Aim: To evaluate the nuclear morphometry and Ki-67 proliferative marker in astrocytomas and to assess the relationship of WHO grade with proliferative activity using Ki-67 immunostaining.

Materials and Methods: This ambispective study was conducted in the Department of Pathology, JSS Academy of Higher Education and Research, Mysuru, Karnataka, India, with a total duration of four years (October 2017 to September 2021). From 35 astrocytoma cases, Haematoxylin and Eosin (H&E) stained slides were retrieved and reviewed appropriately by two pathologists and graded using the WHO criteria. Nuclear morphometric analysis was performed on the H&E slides using Olympus BX-41 research microscope. The parameters evaluated were mean nuclear length, mean nuclear diameter, mean nuclear perimeter, mean nuclear area, Mean Nuclear Roundness Factor (MNRF) and mean nuclear ellipse form. The cases were then stained with Ki-67 antibody. The relationships between WHO grade of astrocytoma and nuclear morphometry and WHO grade with proliferative index was analysed.

Results: According to WHO grading, 4 (11.4%) cases were grade 1, 12 (34.3%) grade 2, six (17.1%) grade 3 and 13 (37.1%) grade 4. Significant correlation was seen between WHO grading and mean nuclear length, diameter, perimeter, area and Ki-67 with p-value <0.001.

Conclusion: Astrocytoma is an extremely heterogeneous disease with unpredictable outcome. The widely used WHO grading is subjective, while nuclear morphometry, using computer assisted image analysis, can ensure more objective assessment. The Ki-67 index could provide valuable information and may compliment the other parameters.