Primary central nervous system lymphoma (PCNSL) is clinically rare, accounting for 0.5%-1.2% of all intracranial tumors and 0.3%-3.8% of non-Hodgkin’s lymphomas (NHL). Non-Hodgkin’s lymphoma can originate in sites other than lymph nodes, including the gastrointestinal tract, bone, thyroid, skin, orbit, testis, lung, and breast. Primary central nervous system non-Hodgkin’s lymphoma is rare. Primary CNS lymphomas are generally non-Hodgkin’s lymphomas that occur in the brain, cerebellum, brainstem, meninges, and spinal cord. On optical microscopic examination, the tumor cells are single and heterogeneous, often arranged in a cuff-like pattern around blood vessels in the early stage, and diffusely distributed without follicle formation in the middle and late stages. The pathological examination is dominated by diffuse B-cell type, but T-cell type or non-T non-B-cell type is rare. Primary CNS lymphoma can occur in any age group and has a subacute onset without characteristic clinical manifestations. It is often caused by local infiltration of brain parenchyma or soft meninges, increased intracranial pressure, tumor compression, and peritumor edema, and may manifest as symptoms of CNS occupancy and intracranial pressure elevation. Ocular choroidal, retinal and vitreous involvement is reported in 12-18% of cases. The diagnosis of primary CNS lymphoma is mainly based on clinical manifestations combined with imaging and other ancillary examinations. Typical CT manifestations: before contrast injection, the white matter in the lower part of the cortex shows isointense to hyperdense lesions; after contrast injection, the lesions are uniformly enhanced, but not strongly. Magnetic resonance imaging has the advantage of being able to scan in multiple directions in the sagittal coronal axis and has a higher resolution than CT, so it has some advantages in understanding the morphology of CNS lymphoma and its relationship with adjacent tissues. It has been suggested that the high signal of perineural edema in CNS lymphoma not only indicates increased interstitial edema at the site, but also contains elements of infiltration and dissemination of tumor cells along the intervascular space. 85% of cases have increased protein concentration on cerebrospinal fluid examination, and only 0%-50% of cases have positive cerebrospinal fluid cytology, and immunohistochemical staining can reveal monoclonal cell populations with malignancy, whereas in The rate of positivity in systemic lymphoma invading the central nervous system can be 70%-95%. It has been suggested that corticosteroids should not be used when primary CNS lymphoma is clinically suspected because they have a lytic effect on lymphocytes and at least 40% of lesions shrink or even disappear completely after use, which makes biopsy difficult and the reaction is non-specific and does not have differential diagnostic value. The prognosis of primary CNS lymphoma is worse than that of systemic lymphoma due to the presence of the blood-brain barrier, involvement of the soft cerebrospinal membrane and the eye, and the presence of biologically extensive infiltrative lesions, and patients will die quickly if left untreated. Unlike other intracranial tumors, primary CNS lymphoma is not effective for surgical resection alone because of its high malignancy and infiltrative growth. If the disease has been considered, it is best to avoid surgical resection and to use stereotactic aspiration biopsy first to confirm the diagnosis. Radiotherapy is the main treatment for this disease and is initially effective in at least 90% of patients with primary CNS lymphoma. The radiation source is usually 60Co high-energy radiation, and the target area includes the whole brain, hard and soft meninges and the spinal cord near the fourth cervical vertebrae. A retrospective study of primary CNS lymphoma showed that 40 – 50 Gy of whole brain radiation therapy is appropriate, with additional local doses up to 60 Gy. If tumor cells are found in the cerebrospinal fluid, whole spinal cord irradiation can be considered. Chemotherapy plays an important role in the comprehensive treatment of primary CNS lymphoma, and commonly used chemotherapeutic agents include high-dose amethopterin and high-dose cytarabine. In years of prospective and retrospective studies, a standard treatment protocol has been gradually developed, namely, after the diagnosis is confirmed, whole brain radiotherapy of 41-50 Gy is administered first, followed by an additional dose of 60 Gy in the lesion and edema area, and then systemic chemotherapy and intrathecal chemotherapy with high-dose methotrexate. The prognosis of primary CNS lymphoma is poor, and the reason for treatment failure is local recurrence. According to the literature, the prognosis is related to the extent of the lesion, the degree of differentiation, KPS score and age, but not to the source of T and B cells and the size of tumor resection.