Fig. 1

The solid lesions are located in the bilateral ventricles and fornix, presenting as isointense on T1WI (a, white arrow) and hypointense on T2WI (b, white arrow) without restricted diffusion (c, white arrow on DWI). Axial SWI demonstrates enlarged veins in the thalamus and located adjacent to the lateral ventricles (d). The lesions demonstrate homogeneous contrast enhancement (e-g, axial (white arrow), sagittal, and coronal T1 with contrast) and hyperperfusion on 3D-ASL MR perfusion imaging (h, black arrow). Open biopsy of the lesions shows diffuse proliferating small lymphocytes (H&E × 200) (i). CD-20 positivity of lymphocytes (× 200) (j). CSF cytology reveals malignant cells, and flow cytometry immunophenotyping reveals a lymphocyte subset with the profile of CD19⁺ (50.81%) (k and l)