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

Abstract

This review addresses the challenges of primary central nervous system (CNS) lymphoma diagnosis, assessment of treatment response, and detection of recurrence. Primary CNS lymphoma is a rare form of extra-nodal non-Hodgkin lymphoma that can involve brain, spinal cord, leptomeninges, and eyes. Primary CNS lymphoma lesions are most commonly confined to the white matter or deep cerebral structures such as basal ganglia and deep periventricular regions. Contrast-enhanced magnetic resonance imaging (MRI) is the standard diagnostic modality employed by neuro-oncologists. MRI often shows common morphological features such as a single or multiple uniformly well-enhancing lesions without necrosis but with moderate surrounding edema. Other brain tumors or inflammatory processes can show similar radiological patterns, making differential diagnosis difficult. [18F]-fluorodeoxyglucose (FDG) positron emission tomography (PET) has selected utility in cerebral lymphoma, especially in diagnosis. Primary CNS lymphoma can sometimes present with atypical findings on MRI and FDG PET, such as disseminated disease, non-enhancing or ring-like enhancing lesions. The complementary strengths of PET and MRI have led to the development of combined PET-MR systems, which in some cases may improve lesion characterization and detection. By highlighting active developments in this field, including advanced MRI sequences, novel radiotracers, and potential imaging biomarkers, we aim to spur interest in sophisticated imaging approaches.

Blood-Brain Barrier Alterations and Edema Formation in Different Brain Mass Lesions

“…Of these PCNSLs, diffuse large cell B-cell lymphoma of the CNS is the most common histologically defined tumor (Wang et al, 2021). PCNSL typically forms either single or multiple hypercellular, diffusely growing lesions (Krebs et al, 2021). Predominant perivascular aggregation, in the form of tight vascular cuffs of neoplastic cells intermingled with reactive non-neoplastic infiltrating inflammatory lymphocytes and macrophages, is typically detected at the periphery (Marcelis et al, 2020).…”

Prognostic factors in primary central nervous system lymphoma

“…Magnetic resonance spectroscopy in PCNSL lesions shows high Choline resonance (a cell membrane marker), a low N-acetylaspartate peak (a neuronal marker) and a large amount of mobile lipids [63]. Unfortunately, these findings are inconstant, nonspecific, and, to date, they do not provide survival information [64].…”

Role of Positron Emission Tomography in Primary Central Nervous System Lymphoma

“…In a retrospective analysis of 127 IC patient scans, Bataille et al reported nine cases of exclusively cortical lesions mimicking a meningioma [ 20 ]. Less frequent presentations involve the eyes, leptomeninges, spine, or vascular system [ 21 ]. Only 1% of PCNSL present with spinal involvement, which typically appears as a solitary infiltrative lesion with multifocal areas of contrast enhancement.…”

“…On MRI, this subtype may appear as diffuse leukoencephalopathy or multiple small infarcts [ 21 ]. In IS patients, lesions are often multifocal, with nodular or peripheral ringlike enhancement reported in up to 75% of cases.…”