Tumefactive demyelination versus primary central nervous system lymphoma on ¹⁸F-fluorodeoxyglucose positron emission tomography magnetic resonance imaging: A twist in the tale

Abstract

Demyelinating lesions of the central nervous system (CNS) are classically known to be hypometabolic on 18 F-Flurodeoxyglucose Positron Emission Tomography ( 18 F-FDG PET). However, demyelinating lesions may show increased tracer uptake on 18 F-FDG PET and can radiologically mimic neoplasm. Delayed tracer uptake on FDG PET is one of the diagnostic hallmarks of primary CNS lymphoma (PCNSL). Here, we present two cases in which the brain lesions showed increased FDG uptake on delayed integrated PET Magnetic Resonance Imaging (MRI), which were pathologically proven as CNS demyelination. Such demyelinating lesions may also act as “sentinel lesions” and potential harbinger of PCNSL on follow-up.

Positron emission tomography and magnetic resonance imaging in primary central nervous system lymphoma—a narrative review

“…A few studies have suggested that delayed imaging of brain tumors (e.g., at 90–480 min) could augment the tumor-to-normal brain contrast ( 91 , 92 ), resulting in improved lesion detection at later imaging time points ( 93 ). However, delayed FDG PET imaging may not corroborate a presumptive diagnosis of primary CNS lymphoma, as false-positive uptake in two cases of demyelination has been observed ( 94 ).…”