Primary central nervous system lymphoma is a rare and highly invasive tumor entity with invasive growth [5]. It mostly affects the central nervous system, including brain, spinal cord, cerebrospinal fluid, cranial nerves, etc., but does not involve the peripheral system. Diffuse large B-cell lymphoma is the main subtype [7].

In this study, it was found that the clinical manifestations of PCNSL patients presented diverse characteristics, with headache and dizziness as the main clinical manifestations, lacking specificity, some of them (single or associated) should point to this diagnostic possibility. The differential diagnosis of CNS lymphoma includes gliomas, metastasis, and inflammatory disorders [8], and disturbance of consciousness or aggravation of disease progression mostly related to the responsible lesions [9]. Radiographic examination showed that the involved sites were mostly located in the brain parenchyma [6], which was generally consistent with the sites mentioned in previous literature. Lesions are usually hipointense on T1 and T2 weighted images. Subependymal spread and meningeal involvement, may be observed [8].The main subtype is non-Hodgkin type diffuse large B-cell lymphoma.

Studies on the pathogenesis of PCNSL [10] suggest that: Most PCNSLS contain B-cell receptors specific to SAMD14 and neurabin-I (SAMD14 and neurabin-I are highly homologous central nervous system proteins), which can induce strong B-cell receptor pathway activation and proliferation through in vivo translation and modification. This may explain that most of the subtypes of PCNSL patients are diffuse large B cells. In this series, patients were detected by CSF flow cytometry, and mature B cell markers were found in the results. When tumor cells were disseminated, abnormal tumor cells were more easily detected in CSF cytology [11].

The diagnosis of PCNSL mainly relies on cerebrospinal fluid flow cytometry or stereotactic biopsy, and the results of stereotactic biopsy may be affected by various factors, which not only cannot improve the long-term survival status of patients, but also causes a high incidence of neurological impairment. The clinical use of corticosteroids can alleviate the clinical symptoms of patients. However, it can also induce apoptosis of tumor cells [1].For patients with acute and critical conditions, if corticosteroids are applied, biopsy should be performed within 24–48 h as far as possible to avoid interference with the results and lead to false negative biopsy results [12]. False negative results have been reported in literature [13] considering that B cells are more sensitive to corticosteroid hormones than T cells, corticosteroid hormones induce tumor B cell transduction and apoptosis, which may reduce the detection of B cells. However, high detection of B cells in secondary biopsies is considered to be due to immune evasion of body cells, and steroid-resistant B cells are selected to survive and replicate in large numbers [13].

Cerebrospinal fluid cell morphology examination is a routine method to screen for the presence of other types of cells in the brain. Tumor cells may occasionally spread into the cerebrospinal fluid, but it will be affected by various factors such as tumor location, the number of cells taken and the skills of the testing personnel. Cerebrospinal fluid cytology combined with flow cytometry can improve the detection rate of PCNSL. Improve the detection rate and accuracy of PCNSL cerebrospinal fluid [14], determine the type of lymphoma and reduce the disease trauma or permanent neurological impairment of patients due to surgical biopsy. Moreover, the classification of PCNSL subtypes by flow cytometry can not only make a clear diagnosis, but also develop a more sensitive and efficient treatment plan with fewer adverse reactions for patients according to the subtype results. While reducing the pain of patients and the financial burden on their families, the clinical diagnosis process is simplified, the accuracy is improved and the scope of use is expanded.

According to some studies [15, 16] the most common parts of PCNSL are cerebral hemisphere, corpus callosum and basal ganglia. The radiographic examination of the patients in this series are basically consistent with those in previous literatures, and the clinical manifestations of PCNSL are varied, mainly related to the location of the brain involved by the tumor. According to literature [15], focal neurological impairment, neuropsychiatric symptoms and increased intracranial pressure accounted for the highest proportion, and the patients in this series showed various manifestations, which was considered to be related to the multiple sites involved in this series of patients, and some patients were complicated with ischemic cerebrovascular disease. According to this series of studies, PCNSL mainly occurs in the elderly, which is basically consistent with relevant literature [17]. At present, with the development of technology, the detection rate of PCNSL is increasing year by year [18]. The literature considers that the median age of diagnosed PCNSL patients is 65 years old, and age has become an independent risk factor for PCNSL [19]. The age of onset of this series of patients is roughly consistent with the literature. The increase of age may lead to low sensitivity and high tolerance of patients to central symptoms caused by neoplastic cell hyperplasia, and middle-aged and elderly patients are less likely to tolerate adverse reactions caused by surgery and radiotherapy and chemotherapy, resulting in worse prognosis than young and middle-aged adults [19].

At present, there is no uniform and clear standard for the treatment of PCNSL. Because chemotherapy drugs for systemic lymphoma do not easily penetrate the blood–brain barrier, drugs for systemic lymphoma are less effective. Literature studies [20, 21] have shown that irutinib in the treatment of recurrent or refractory primary central nervous system lymphoma in mice can reach therapeutic concentration in cerebrospinal fluid. It also prolongs the survival period of mice, but the traditional treatment methods of international and domestic standards are currently used: high-dose methotrexate (HD-MTX) [1] combined with chemoradiotherapy can delay the survival period of some patients [22], but the combination of chemoradiotherapy may cause neuropsychiatric symptoms, and whole brain radiotherapy to a large extent causes more serious neurotoxicity and high recurrence rate for elderly patients [23]. Further research on the molecular biology and subtypes of PCNSL, the combined application of targeted drugs and the experimental development of a variety of therapeutic means may greatly improve the level of clinical diagnosis and treatment, and ultimately enable PCNSL patients to obtain long-term benefits and higher quality of life.