MR images in a 53-year-old man with diffuse large B-cell PCNSL belonging to the PR group (A1, A2, A3, before therapy; B1, B2, B3, after 1 cycle of chemotherapy; C1, C2, C3, after 5 cycles of chemotherapy). An apparent enhanced tumor on the bilateral frontal lobe and corpus callosum (A1). On the DWI, the tumor is apparently hyperintense in relation to adjacent structures (A2, B2, C2). The baseline ADCmin of the tumor was 420 × 10−6 mm2/s (A3). After 1 cycle of chemotherapy, the size of the tumor has decreased slightly (B1, B2) and the ADCmin has increased to 764 × 10−6 mm2/s (B3). After 5 cycles of chemotherapy, the size of the tumor has continued to decrease (C1), while the ADCmin has decreased to 617 × 10−6 mm2/s (C2, C3).