The labyrinth of pyrexia of unknown origin: a case of intravascular diffuse B cell lymphoma.

Intravascular large B cell lymphoma (IVLBCL) is a rare, aggressive extranodal B cell lymphoma, classified as a subset of diffuse B cell lymphoma. IVLBCL typically occurs in elderly persons and the clinical heterogeneity of the condition makes the diagnosis elusive in most cases. Most of the reported cases have been in the Asian population with the majority of the cases being diagnosed postmortem. We present a unique case of IVLBCL in a 65-year-old Caucasian male who presented with fever of unknown origin.