Primary central nervous system (CNS) lymphoma (PCNSL) is an uncommon extranodalnon-Hodgkin lymphoma often presenting as a single brain lesion within the CNS.On histopathological evaluation of PCNSL a positive CD10, which is frequentlyobserved in systemic diffuse large B-cell lymphoma, is present in approximately10% of PCNSL. The gene discussed is MME; the disease is diffuse large B-cell lymphoma.