Clinical Benefits of Arterial Spin-Labeling Magnetic Resonance Imaging for Primary Diffuse Large B-cell Lymphoma of the Central Nervous System Presenting With Lymphomatosis Cerebri: A Case Report.

Of the primary central nervous system (CNS) lymphomas, diffuse large B-cell lymphoma of the CNS (CNS-DLBCL) is an aggressive extranodal lymphoma that originates in the CNS. Lymphomatosis cerebri (LC) is an exceptionally rare subtype, posing diagnostic challenges due to the absence of abnormal enhancement and making the identification of suitable biopsy sites difficult. Arterial spin-labeling magnetic resonance imaging (ASL-MRI) is a non-invasive MRI technique that quantifies tumor blood flow. This report presents a case of CNS-DLBCL with LC, which was evaluated and biopsied using ASL-MRI of the brain. Herein, we present a case of a 32-year-old female who presented with abnormal involuntary movements and cognitive impairments. She underwent an MRI which showed a diffuse and infiltrative lesion in the bilateral basal ganglia, showing a high signal intensity area on fluid-attenuated inversion recovery (FLAIR) images with no contrast enhancement. Computed Tomography scans and Gallium-67 scintigraphy showed no abnormal uptake throughout the whole body. Although she received corticosteroid treatments, subsequent MRI showed an enlarged lesion, and she underwent a brain biopsy. The biopsy site was determined based on high perfusion demonstrated by ASL-MRI and the histological findings positive for B-cell markers led to diagnoses of CNS-DLBCL, specifically LC. Her symptoms improved following high-dose methotrexate and whole-brain irradiation. Subsequent MRI scans showed a dramatic improvement, and the high perfusion observed in the ASL-MRI disappeared. This report has emphasized the critical role of histopathology in diagnosing CNS-DLBCL presenting with LC, a highly aggressive lymphoma requiring prompt treatment. In this case, high ASL-MRI signal intensity indicated an increased area of tumor cell density suitable for biopsy. This is the first report to establish a relationship between cell density and ASL-MRI signal intensity in LC. The challenge in locating the optimal biopsy site due to the lack of contrast enhancement and the difference in tumor cell densities within high signal intensity areas on FLAIR imaging is presented. ASL-MRI provides information on tumor blood flow (TBF), which may be associated with higher tumor cell density, making it a valuable tool for identifying suitable biopsy sites. Thus, ASL-MRI is clinically beneficial for the biopsy of LC cases that show high signal intensity on FLAIR images without contrast enhancement.