MRI features of primary central nervous system lymphomas at presentation.

Pretreatment MRI examinations of 40 immunologically competent patients with primary CNS lymphoma (PCNSL) were evaluated (24 men, 16 women, median age 63 years). Seventy lesions were found (mean size: 19.9 mm). The number of lesions ranged from one (n = 25) to six (n = 1). The most frequent locations were the cerebral hemispheres (n = 22), the corpus callosum (n = 11), and the basal ganglia (n = 11). Cerebellar manifestations were found in 10 patients. Ocular (n = 2) and medullary cord (n = 1) manifestations were rare. Contrast enhancement was encountered in all lesions. Although 39 patients had lesions adjacent to the CSF space, leptomeningeal spread was only present in five patients. Necrosis was seen in two lesions only. Edema was extensive in 24 patients, moderate in 11 patients, and absent in five patients. Contrast-enhancing lesions in contact with the subarachnoid space and without necrosis are characteristic of PCNSL.