MRI patterns of non-enhancing T2-FLAIR hyperintense lesions with dynamic change in primary CNS lymphoma

The nature of non-enhancing T2-FLAIR hyperintense lesions that are not contiguous with the enhancing tumor site at baseline in primary central nervous system lymphoma (PCNSL) remains unclear. Our aim was to explore the incidence, location, morphology, and dynamic changes of these non-enhancing T2-FLAIR hyperintense lesions in PCNSL.

We retrospectively reviewed patients diagnosed with immunocompetent PCNSL at our institution. We identified and evaluated T2-FLAIR hyperintense lesions without enhancement that showed a marked decrease or complete disappearance on MRI after treatment. MRI characteristics of PCNSL at initial presentation were analyzed and compared between patients with and without non-enhancing T2-FLAIR hyperintense lesions.

Among 87 patients, 10 patients (11.5%) were found to have non-enhancing T2-FLAIR hyperintense lesions located at a distance from the enhancing tumor site at baseline that showed a marked decrease or disappearance after treatment. The locations of these lesions were as follows: the juxtacortical and deep white matter (7 lesions), periventricular white matter (2 lesions), basal ganglia (1 lesion), and infratentorial area (1 lesion). Baseline MRI characteristics in patients with non-enhancing T2-FLAIR hyperintense lesions exhibited a higher rate of multiple enhancing lesions (P = 0.027) and bilateral enhancing lesions (P = 0.011) compared to patients without non-enhancing T2-FLAIR hyperintense lesions.

In PCNSL patients, non-enhancing T2-FLAIR hyperintense lesions at a distance from enhancing tumor lesions, which are potentially neoplastic in nature, were not uncommon. Our findings raise the question of whether these non-enhancing lesions should be incorporated into the initial evaluation of tumor burden. This issue warrants further investigation.