Primary central nervous system lymphoma in immunocompetent patients: spectrum of findings and differential characteristics.

Primary central nervous system (CNS) lymphomas are uncommon and their management differs significantly from that of other malignant tumors involving the CNS. This article explains how the imaging findings often suggest the diagnosis early. The typical findings in immunocompetent patients consist of a supratentorial intraaxial mass that enhances homogeneously. Other findings to evaluate include multifocality and incomplete ring enhancement. The differential diagnosis of primary CNS lymphomas should consider mainly other malignant tumors of the CNS such as glioblastomas or metastases. Primary CNS lymphomas tend to have less edema and less mass effect; they also tend to spare the adjacent cortex. Necrosis, hemorrhage, and calcification are uncommon in primary CNS lymphomas. Although the findings in morphologic sequences are characteristic, they are not completely specific and atypical types are sometimes encountered. Advanced imaging techniques such as diffusion or especially perfusion provide qualitative and quantitative data that play an important role in differentiating primary CNS lymphomas from other brain tumors.