Intravascular Large B-Cell Lymphoma Presenting as Recurrent Cryptogenic Strokes: A Diagnostic Challenge.

Intravascular large B-cell lymphoma (IVLBCL) is a rare malignancy and is a challenging diagnosis to make given its varied clinical presentation. Here, we present the case of a 69-year-old male who presented with multiple cryptogenic strokes. Despite multiple hypercoagulable and malignancy workups, no etiology was identified, with multiple CT scans negative for any masses. Ultimately, a vascular abnormality was noted on a CTA of the head and neck, and IVLBCL was diagnosed on biopsy. The patient was initiated on R-CHOP and had improvement in his neurological status after the initiation of chemotherapy, and his ClonoSeq MRD testing is negative. This case is of interest given the lack of imaging findings for this patient prior to diagnosis as all of his CT scans were negative, making it a challenge to diagnose him as well as monitor his response to treatment. Additionally, his case highlights the importance of ClonoSeq MRD testing, which allows for the detection of even minimal amounts of disease in tracking response to treatment.