Background: Astrocytomas are considered the most prevalent central nervous system [CNS] tumors. Diffuse astrocytomas are evaluated by a three-tiered system [II, III, and IV] according to the 2007 WHO classification. The WHO grading scheme is based on the existence or lack of four histological features: mitosis, nuclear atypia, microvascular proliferation, and necrosis. Pilocytic astrocytoma is classified as WHO grade I in histological grading of localized astrocytic tumors. In many cases of human neoplasms, including astrocytoma, p53, and Ki67, the expression increases, especially in aggressive and high-grade tumors.
The Aim of the work: We aimed to validate the p53 and Ki 67 immunohistochemical expression in various grades of astrocytic tumors and correlate this expression with clinicopathologic findings and histopathologic grading.
Patients and methods: Immunohistochemical analysis [IHC] of p53 and Ki67 were used to evaluate 45 paraffin-embedded samples, which included different grades of astrocytoma [10 participants of pilocytic astrocytoma, 12 participants of diffuse astrocytoma grade II, 9 participants of anaplastic type, and 14 participants of glioblastoma type]. Tumor tissue blocks and clinical information of the cases were gathered from the files of Pathology Department of Al-Azhar University Hospitals [Al-Hussein & Al-Zahraa] and from the archives of some private laboratories from March 2018 to June 2021.
Results: Immunohistochemical [IHC] expression of p53 and Ki 67 had a significant positive association with histopathological grading of astrocytoma. High expressions were detected in high-grade astrocytoma [grade III, IV] versus low-grade types [I, II]. 
Conclusion: p53 and Ki 67 immunohistochemical expression is up regulated in high-grade astrocytoma. Their overexpression seems to indicate a more malignant phenotype.