Neuroradiological findings in primary cerebral lymphomas of non-AIDS patients.

Primary central nervous system lymphomas (PCNSL's) are rare tumours which generally accounted for 1.0-1.5% of all intracranial neoplasms. However, within the last decade the frequency of cerebral lymphomas has dramatically increased. We retrospectively analysed the neuroradiological findings (computed tomography (CT), MRI, angiography) in 37 patients with PCNSL. Thirty patients with the clinically and neuroradiologically suspected diagnosis of cerebral lymphoma underwent CT- or MRI-guided stereotactic biopsy. In seven cases an open surgical intervention was performed. Preoperatively, CT with and without contrast medium was performed in all but two cases. Twenty-eight patients received MRI (axial SE T2 weighted, triplanar SE T1 weighted, triplanar SE T1+Gadolinium). Additionally, in 9 patients cerebral angiography was performed. Typical neuroradiological patterns are: (1) iso- or hyper-density (85.5%) on unenhanced CT scan with marked contrast enhancement (87.7%); (2) infiltration/contact of leptomeningeal and/or ependymal spaces (97.3%); (3) hyperintensity on T2 with moderate oedema (80.3%). Histopathological work-up included conventional and immunohistochemical stains performed on formalin fixed and paraffin embedded bioptical specimen. Despite widely used preoperative dexamethasone treatment, an accurate histopathological diagnosis of PCNSL of B cell type was established in all cases except one. The high percentage of accurate histopathological diagnosis was based on: (1) great mean sample volume per biopsy site; (2) great number of biopsies in patients suspected to have cerebral lymphomas; and (3) MR-guided stereotactic procedures if the lesion was not clearly identifiable on CT scan.