Immunocompetent patient with isolated primary fourth ventricle lymphoma. Unusual diagnosis, their pitfalls, and challenges.

Background: Primary central nervous system lymphoma (PCNSL) is an uncommon lesion and represent 4% of all central nervous system (CNS) cancers. There have been few reports of localized isolated lymphoma developing in the fourth ventricle, with only 8 previous cases described. We present a case of an immunocompetent patient with isolated fourth ventricle lymphoma who did not have diffusion-weighted imaging (DWI) restriction.