Fig. 1

The radiological, pathologic diagnosis and treatment of case 1. Brain contrast-enhanced MRI (a-d): A space-occupying lesion about 3.9 × 2 × 1.6 cm at the corpus callosum with a ring enhancement before treatment (in Apr, 2021) (a); Having a partial response (PR) after 2 months treatment (In August, 2021) (b); Keeping a PR after 4 months treatment (In October, 2021) (c); Achieving a complete response (CR) after 8 months treatment (In March, 2022) and keeping a CR after 19 months treatment (In February, 2023) (d). Histological characteristics (e-h): Diffuse distribution of tumor cells with flaky coagulation necrosis were found. There were a large amount of lymphoid cells proliferation especially around the blood vessels and lymphocyte infiltration in blood vessel wall. The volume of some cells is medium to small, and other cells are medium to large. The nucleus is slightly irregular, and nucleolus enlargement and nuclear division were found (H&E staining, original magnification×200) (e); The diffuse expression of CD20-positive tumor cells ( immunohistochemical staining, original magnification×200) (f). The tumor cells with positive expression of Pax-5 (immunohistochemical staining, original magnification×200)(g). The positive EBV-encoded small RNA (EBER) was found (situ hybridization, original magnification×200) (h). Treatment regimen adjustment (i)