Case report: Ventricular primary central nervous system lymphoma with partial hypointensity on diffusion-weighted imaging.

Introduction: Primary central nervous system lymphoma (PCNSL) is infrequent and represents 3. 1% of primary brain tumors. And the lesions that are restricted to the ventricular system, particularly the third ventricle, are even rarer. There are few pieces of literature or case reports to date. We report a case of PCNSL with partial hypointense on diffusion-weighted imaging (DWI) located in the lateral and third ventricles. Then we reviewed almost all case reports of ventricular PCNSLs in the last 20 years, discuss the imaging presentation, other ventricular tumors with similar imaging findings, and primary treatment measures. Case presentation: A 78-year-old man presented with memory loss and poor responsiveness for one week without obvious precipitating factors. Magnetic resonance imaging (MRI) showed lesions in the third ventricle and left lateral ventricles, which were slightly hypointense on T1-weighted imaging (T1WI), and isointense to slightly hypointense on T2-weighted imaging (T2WI). On DWI, the left lateral ventricular lesion was hyperintense, while the third ventricular lesion was hypointense. After the surgical procedure, the pathology and immunohistochemistry revealed diffuse large B-cell lymphoma (DLBCL). Conclusions: Ventricular PCNSL is quite rare, and may be confused with other tumors in the same position. However, PCNSL differs from other central nervous system tumors in that it is primarily treated with chemotherapy and/or radiation therapy. So, it is important to recognize PCNSL and differentiate it from other tumors, considering its implications for management planning.