Intravascular Large B Cell Lymphoma (IVLBCL) is a rare subtype of Diffuse Large B Cell Lymphoma, characterized by B cell proliferation within blood vessel lumens without apparent extravascular masses. IVLBCL often manifests with nonspecific signs such as fever of unknown origin, as well as highly variable proportions of neurological, hematologic, and cutaneous findings, rendering it diagnostically challenging. A 66-year-old woman presented to the ED with worsening hypotension, nausea, and malaise over the past year. Despite multiple admissions, prior workups were inconclusive, except for splenomegaly.