Central nervous system lymphoma: a morphological MRI study.

OBJECTIVES: The aim of the present study was to evaluate morphological MRI findings in histologically-proven central nervous system lymphoma (CNSL) at time of their first appearance, and to describe dynamic changes on repeat MRI before the diagnosis was histologically proven.

METHODS: We retrospectively evaluated the MRI examinations of 74 patients with histologically-proven CNSL (10 secondary CNSL, 64 primary PCNSL; 10 immunocompromised, 54 immunocompetent). In 43 patients, we evaluated the evolution of CNSL on MRI before the diagnosis was proven.

RESULTS: Primary CNSL was typically localized supratentorially (63%), with multiple (59%) or infiltrative (36%) lesions showing diffusion restriction (98%), often (87%) reaching the brain surface. In approximately 50% of patients, meningeal, ependymal or cranial nerve involvement was found. We detected significant differences in enhancement patterns between immunocompromised and immunocompetent patients; non-homogenous enhancement present in 50% of immunocompromised patients. We did not find any significant differences in MRI appearance between primary and secondary CNSL. Regression was evident after corticosteroid treatment in 52% of patients; however, in 16% of cases overall progression was observed.

CONCLUSION: CNSL generally presents as an infiltrative lesion or multiple homogenously-enhancing lesions of the brain in contact with the brain surface. Involvement of the corpus callosum, cranial nerves, ependyma or meninges is common. No significant differences between primary and secondary CNSL were detected, however differences in enhancement type between immunocompromised and immunocompetent primary CNSL patients were found. We stress the variability of MRI findings in the course of the disease and also the variable response to corticotherapy.