Lymphomas-Part 1.

Primary central nervous system lymphomas are aggressive, high-cell-density tumors. There is recent increase in their incidence in immunocompetent patients. Knowledge of imaging findings on computed tomography and conventional MR imaging is important to suggest the diagnosis. Moreover, information obtained from advanced MR imaging techniques, such as diffusion-weighted imaging, diffusion tensor imaging, MR spectroscopy, perfusion-weighted imaging, and dynamic contrast-enhanced studies, increases diagnostic confidence and helps distinguish them from other aggressive intracranial tumors. This article discusses typical imaging findings of primary and secondary central nervous system lymphomas on computed tomography and conventional MR imaging, advanced MR imaging techniques, and changes related to steroid therapy.