MRI patterns in recurrence of primary CNS lymphoma in immunocompetent patients.

Purpose: Primary CNS lymphomas (PCNSL) are highly malignant non-Hodgkin's B-cell lymphoma restricted to the CNS. While MRI features of PCNSL at initial presentation have been comprehensively described, literature on MRI-characteristics at relapse is sparse. The purpose of this study was to investigate anatomic location and contrast enhancement patterns at PCNSL recurrence by cranial MRI.

Methods: Sixteen immunocompetent patients (9 men, 7 women, median age 65 years) with histologically proven PCNSL and initial response to a standardized polychemotherapy, but suffering from a relapse were consecutively recorded. Native and contrast-enhanced MRI examinations carried out at initial presentation and at time of relapse were compared. Anatomical site of parenchymal enhancement, frequency and presence of non-parenchymal contrast enhancement (i.e. ventricular, superficial, subependymal) patterns at initial presentation and at relapse were recorded and compared.

Results: Local recurrence was found at the site of the initial tumor presentation in four of the 16 cases. Six of 11 patients presenting a unilateral PCNSL at initial presentation had a bilateral involvement at relapse. In two cases, recurrence appeared solely on the contralateral side without involvement of the hemisphere initially affected. At both dates, subependymal enhancement was the most often found non-parenchymal pattern (six at initial presentation, and five at relapse). The number of patients with a ventricular contrast enhancement increased from one at initial presentation to four at relapse.

Conclusions: PCNSL tend to recur in different parenchymal anatomic sites as compared with the site of the initial tumor presentation. Contrast-enhancing non-parenchymal lesions are also frequent and might change their pattern at relapse.