The MRI features of central nervous system lymphoma (PCNSL) and its implications in the biopsy.

Objective To characterize the MRI findings of primary central nervous system lymphoma(PCNSL) in immunocompetent patients.Methods The MRI brain imaging of Patients with pathological proved PCNSL were analyzed retrospectively.From Jan 2000 to Dec 2008,35 patients were admitted into the cancer center and the first affiliated hospital of Sun Yat-sen University.Locations,sizes,numbers,enhancement characteristics of lesions,edema around the tumor and involvement of the corpus callosum on MRI were recorded and analyzed.Results Fifty-one lesions were found in 35 patients.The number of lesions ranged from 1(n=26) to 5(n=9) with a mean of 1.7.The most frequent locations were the cerebral hemispheres(27/51,52.9%),basal ganglia-thalamus(9/51,17.7%) and corpus callosum(8/51,15.7%).Contrast enhancement was found in all patients.Among them,34 lesions exhibited homogeneous enhancement pattern and 17 lesions had inhomogeneous enhancement pattern.First,second and third levels of peritumoral edema were found in 14,31 and 6 lesions,respectively.Nine patients were diagnosed by stereotaxis biopsy at contrast enhanced lesion site or the margin of the tumor.Conclusions The cerebral hemisphere is the commonest location of PCNSL.MRI features of PCNSL are mass,contrast-enhancing lesions with a diameter of at least 20 mm.The margin of lesion or the location with greatest contrast-enhancement would be the best site for biopsy.