Brain, Primary diffuse large B cell lymphoma of the central nervous system

Primary CNS DLBCL is a unique entity defined by the WHO as an extranodal non-Hodgkin lymphoma restricted to the brain or eye; lymphomas of the dura, intravascular large B cell lymphoma, CNS involvement by systemic lymphomas, and immunodeficiency-associated lymphomas are excluded. Overall, primary CNS DLBCL is rare and most commonly occurs in older adults. Microscopically, lymphoma cells usually show a diffuse growth pattern while an angiocentric pattern and single-cell infiltration of the brain parenchyma can be seen at the periphery. The cells are large with round to irregular nuclei and prominent nucleoli. Tumour cells stain for B cell markers (CD20, 79a, etc), MUM1 (90%), bcl2 (60-80%), and sometimes CD10 (10-20%). Bcl2 is usually positive. EBV is negative, in contrast to CNS DLBCL associated with HIV or immunocompromise. Prognosis is generally unfavourable.