CNSC-36. INDOLENT INTRAVASCULAR LARGE B-CELL LYMPHOMA (IVLBCL) ORIGINALLY PRESENTING AS A STROKE MIMIC

Abstract

Abstract BACKGROUND IVBCL is a rare subtype of extranodal diffuse large B-cell lymphoma, characterized by the growth of neoplastic cells in blood vessels with no other apparent extravascular mass, making diagnosis a challenge. It usually has an aggressive and fast-paced course; however, there is limited data regarding incidence due to its rarity. CASE A 73 year-old woman presented with progressive gait worsening a year prior to presentation to our institution. Her symptoms then developed to include left-sided hemiparesis with associated headaches, warranting a local emergency department visit. Brain magnetic resonance imaging (MRI) without contrast showed a Flair hyperintense lesion in the right MCA territory with restricted diffusion, assumed to be an ischemic stroke, and she was started on stroke prevention measures. The patient continued to decline, becoming wheelchair-bound and developing short-term memory loss, chronic headaches, and pseudobulbar affect. Repeat brain MRI without contrast five months later showed progression of the Flair hyperintensity to the left hemisphere with restricted diffusion. Brain MRI with contrast followed, revealing subtle enhancement. Vessel imaging was unremarkable, and cerebrospinal fluid (CSF) analysis was normal with negative cytology and flow cytometry, yet elevated beta-2-microglobulin at 3.25 mcg/mL. A year after symptoms onset, the patient presented to our Neuro-Oncology clinic. Repeat Brain MRI with contrast and spectroscopy showed progression on the left-sided lesion with persistent restriction diffusion and enhancement, prompting a biopsy. Pathology confirmed large B cell lymphoma. PET-CT body scan showed no evidence of systematic disease. The patient was treated with Rituximab, Methotrexate, Vincristine, and Procarbazine (RMVP) with complete response demonstrated by complete resolution of the diffusion restriction and symptoms improvement. CONCLUSIONS Although IVLBCL is known for being a fast progressive disease, we present a case of indolent course delaying diagnosis. Unexplained progressive neurological symptoms with restricted diffusion on MRI should prompt consideration for this diagnosis.