Tehran University of Medical Sciences International Journal of Hematology-Oncology and Stem Cell Research 2008-2207 20 3 2026 09 29 249 256 Zujajah Hameed Department of Pathology, Shifa International Hospital, Islamabad, Pakistan Fatima Sharif Department of Pathology, Shifa International Hospital, Islamabad, Pakistan Imran Ahmad Department of Pathology, Shifa International Hospital, Islamabad, Pakistan Maliha Aziz Department of Clinical Research, Shifa International Hospital, Islamabad, Pakistan 2025 08 16 2026 08 08 Background: Primary CNS lymphoma (PCNSL) is a rare form of extranodal lymphoma, representing 3 to 4% of brain tumors. We aim to report the clinicopathological features and predictors of survival in patients with PCNSL. Materials and Methods: This retrospective study was conducted at Shifa International Hospital, Pakistan. Patients diagnosed with PCNSL from 2018 to 2023 were included. The Hans algorithm was used to further categorize cases of high-grade lymphoma. Data were analyzed using IBM® SPSS Statistics Software Version 26. Results: Fifty-two patients were diagnosed with PCNSL during the study period, out of whom twenty-seven patients had complete clinical and laboratory data available. From these 27 patients, 14 (52%) were male. Mean age was 48.78 ± 13.46 years. Twenty-four (88.9%) patients were immunocompetent and none had HIV infection. On radiology, a solitary lesion was seen in 19 (70.4%) patients with parietal lobe being the most common location in 8 patients. Twenty-six patients were diagnosed with high-grade non-Hodgkin B-cell lymphoma whereas one patient had low-grade non-Hodgkin B-cell lymphoma. Seven patients expired, with median survival of five months (range 1–31 months). Ki-67 proliferative index >80% was the only factor identified as significantly associated with decreased overall survival (p<0.05). Conclusion: PCNSL is a rare and aggressive disease. High Ki-67 proliferative index is a significant predictor of overall survival in these patients. Lack of association of HIV, frequent occurrence of Bcl6 positivity and a single case of low-grade lymphoma were unique features identified in our study population.   https://ijhoscr.tums.ac.ir/index.php/ijhoscr/article/view/2506 https://ijhoscr.tums.ac.ir/index.php/ijhoscr/article/download/2506/1140