OCT4 and Nestin Expression in the Microenvironment of Primary Central Nervous System Lymphomas

<b>Background:</b> Angiogenesis is essential for the survival of neoplasms. Our aim was to describe the clinical profile of primary central nervous system lymphoma (PCNSL) patients at our institution and explore the immunohistochemical expression of OCT4 and nestin in the tumor microenvironment especially in relation to angiogenesis. <b>Materials and Methods:</b> All cases of PCNSL from 2016 to 2022 were retrospectively studied, and clinical and radiological characteristics of the patients were obtained. Descriptive statistics were used. <b>Results:</b> 26 cases were studied; 24 cases (92.3%) were B-cell lymphomas: 23 diffuse large B-cell, and one Burkitt lymphoma. 7.7 % were of T lineage. 13 women and 13 men, had age ranges between 33-71 years (mean 58.16 years). Three patients (12 %) had immunosuppression. Nestin staining revealed hypertrophic astrocytes forming patches about blood vessels with positive cytoplasmic staining in endothelium and pericytes (5-10% of the intra-tumor arterioles). These findings were seen in both B and T lymphomas. OCT4 nuclear expression was only observed in five large B-cell lymphomas and seemed to have relationship with mitoses/HPF (high power field). <b>Conclusion:</b> The novel finding of endothelial, pericytes and hypertrophic astrocytes staining with nestin, points to the involvement of stem cells promoting angiogenesis as a result of a dialogue between neoplastic cells and vascular stem cells. OCT4 expression seems to have a relationship with cell proliferation whose clinical significance should be investigated in prospective studies.