SirThis article is a report of a case with primary central nervous system (CNS) lymphoma, with impending brain herniation due to a huge mass, and surgical reduction was effective in obtaining neurological improvement.[1] Usually the standard therapy for primary CNS malignant lymphoma, at present, is high-dose methotrexate therapy with or without radiotherapy, and surgery is mainly limited to tissue diagnosis, due to its diffusely infiltrative nature. However, in some cases, such as a huge tumor with impending herniation or CNS lymphoma cases with intratumoral hemorrhage, emergency surgery for mass reduction is required.Intracerebral hemorrhage in primary CNS lymphoma is rare, but higher vascular endothelial growth factor (VEGF) immune reactivity in hemorrhagic cases is observed compared to non-hemorrhagic cases.[2345] Also, serum elevation of VEGF levels are predictors of poor prognosis. In the previously reported cases of intratumoral hemorrhage in primary CNS lymphomas, emergent craniotomy and removal of mass reduction was performed. Although impending herniation of primary CNS lymphomas is rare, a mass reduction surgery should sometimes be considered in such unique cases.