Intravascular large B-cell lymphoma (IVLBCL) is a rare form of extranodal diffuse large B-cell lymphoma characterized by the proliferation of lymphoma cells in the lumen of small blood vessels. Clinical presentation varies among reported cases and diagnosis can be challenging for both clinicians and pathologists. We report a case of a 64-year-old female with a history of prolonged fever. Diagnosis was suspected clinically due to thrombocytopenia and elevated serum lactate dehydrogenase after exhausting work-up for an infectious etiology. IVLBCL was established on post-mortem examination upon finding infiltration of CD20-positive neoplastic cells in several organs in the absence of lymph node involvement.