Primary central nervous system malignant lymphoma (PCNSML) accounts for about 0.5% to 1.5% of intracranial tumors, meaning that with modern diagnostic methods, only the presence of malignant lymphoma of the central nervous system can be detected, while lymphoma of other sites is not found. Since there is no lymphoid tissue and its drainage structures in the brain tissue, the cellular origin of PCNSML may be the germinal center of B cells, or it has been suggested to originate from undifferentiated multipotential stem cells around the blood vessels in the brain. The clinical manifestations and imaging examinations of PCNSML are non-specific, and preoperative diagnosis is difficult. Clinical symptoms of increased intracranial pressure such as headache and vomiting are the most common, followed by limb weakness or numbness, and mental symptoms are rare. The clinical manifestations are: 1, rapid progression and short duration of disease; 2, early appearance of symptoms of increased intracranial pressure; 3, tendency of multiple lesions; 4, more males than females; 5, lesions are mostly located on the curtain. CT usually shows isointense or high-density single or multiple masses with clear borders, and the lesions are uniformly enhanced after intravenous contrast injection, usually without a central hypointense area, with mild to moderate edema around the lesions. MRI shows slightly low or equal signal in T1-weighted image and equal or slightly high signal in T2-weighted image; apparent homogeneous enhancement; most of the tumors are large and have obvious occupancy effect, but the surrounding edema is mild. This is one of the characteristics of the tumor. Although the diverse imaging presentation of this tumor makes clinical diagnosis difficult, imaging remains an important basis for diagnosis and is usually differentiated from metastases, gliomas, and infectious diseases. Hormones can cause some lesions to fade for a short time, which can lead to clinical misdiagnosis and mismanagement. The diagnosis of PCNSML can only be made on the basis of imaging, and cerebrospinal fluid examination can be helpful. Cerebrospinal fluid centrifugation and cell collection by immunocytological examination can increase the positive detection rate of tumor cells, which is less than 50%. Pathological examination is a reliable method to confirm the diagnosis of PCNSML. Pathological features are: 1. Tumor cells are arranged centripetally around blood vessels and form vascular sets; 2. Giant cell infiltration and astrocyte reaction are common; 3. No significant vascular endothelial cell proliferation; 4. Positive expression for leukocyte common antigen (LCA); 5. Intracranial malignant lymphomas are mostly of B-cell type, and very rarely of T-cell or non-T non-B-cell type. PCNSML is histologically similar to other systemic lymphomas, but its prognosis is worse, with a natural survival of 1.8 to 3.3 months, and surgical treatment alone does not prolong patient survival. Most scholars believe that clinical consideration of PCNSML is best done by stereotactic biopsy to clarify the diagnosis, and surgical treatment can be considered if the lesion is located in a non-functional area. Adrenocorticotropic hormone can inhibit tumor growth and even make the lesions disappear, but the effect is not long-lasting. It can be used to control symptoms in patients with confirmed diagnosis or to control the occurrence of cerebral edema during radiotherapy. Radiotherapy is an important treatment for this disease and should be administered early after surgery, usually 40-50 Gy of whole brain irradiation followed by 60 Gy of local irradiation to the lesion or edema area.