Tumor-like Lesions in Primary Angiitis of the Central Nervous System: The Role of Magnetic Resonance Imaging in Differential Diagnosis

Abstract

Primary Angiitis of the Central Nervous System (PACNS) is a rare disease and its diagnosis is a challenge for several reasons, including the lack of specificity of the main findings highlighted in the current diagnostic criteria. Among the neuroimaging pattern of PACNS, a tumefactive form (t-PACNS) is a rare subtype and its differential diagnosis mainly relies on neuroimaging. Tumor-like mass lesions in the brain are a heterogeneous category including tumors (in particular, primary brain tumors such as glial tumors and lymphoma), inflammatory (e.g., t-PACNS, tumefactive demyelinating lesions, and neurosarcoidosis), and infectious diseases (e.g., neurotoxoplasmosis). In this review, the main features of t-PACNS are addressed and the main differential diagnoses from a neuroimaging perspective (mainly Magnetic Resonance Imaging-MRI-techniques) are described, including conventional and advanced MRI.

Keywords: HGG; MRI; PACNS; PCNSL; TDL; glioma; mass-like lesion; neurotoxoplasmosis; sarcoidosis; tumefactive lesion; tumor-like lesion.

Figure 1

Conventional MRI findings in t-PACNS. A cortico-subcortical left frontal lesion is illustrated, hyperintense on T2/FLAIR (axial and coronal views) and T2WI and hypointense on T1-WI. DWI and ADC images show a corresponding hypo- and hysointense signal, respectively. In the GRE–T2* sequence, small punctate hypointense regions are evident within the lesion. ADC_min values are reported in the figure with the corresponding region of interest (ROI) (red circle).

Figure 2

Post-contrast MRI sequences in the same patient depicted in Figure 1, showing a peripheral and mainly cortical rim of contrast enhancement.

Figure 3

Another example of MRI findings in a patient with t-PACNS, showing a subcortical right frontal mass lesion with peripheral contrast enhancement surrounded by edema and including SWI hypointense foci. ADC_min values are reported in the figure with the corresponding ROI (red circle).

Figure 4

Advanced MRI technique findings in t-PACNS. The subcortical peripheral-enhancing right frontal lesion is characterized by low rCBV values on DSC-MRI.

Figure 5

Conventional MRI findings in PCNSL. The T2-weighted imaging (T2WI) signal shows a mass lesion characterized by hyperintensity with mottled internal hypointense areas. On post-contrast T1-weighted imaging, a lesional enhancement is evident with some hypoenhancing areas within it. DWI with ADC shows a prevalent internal restriction. ADC_min values are reported in the figure with the corresponding region of interest (ROI) (red circle).

Figure 6

Advanced MRI findings in PCNSL. Dynamic susceptibility contrast (DSC) MRI measures of rCBV define microvascular volume as an indicator of tumor-related angiogenesis. Diffusion tensor imaging–fractional anisotropy color-coded (DTI-FAcc) shows the integrity of white matter tracts. ¹HRS spectroscopy demonstrates a pathological increase in the Cho peak and a decrease in the NAA peak (Cho/Cr 3.30, NAA/Cho: 0.36 e Cho/NAA 2.75).

Figure 7

MRI pattern in MS-related TDL. A subcortical white matter heterogeneously hyperintense on T2/FLAIR lesion is shown, with a mild tumefactive effect on the ventricular wall. In DWI sequences, there is not a clear restriction. Post-GBCA T1W sequences show heterogenous enhancement with an incomplete ring pattern. DSC-MRI shows a hypoperfusion of the mass-like lesion.

Figure 8

MRI pattern in HGG. The MRI shows a parietal lesion with mass effect and surrounding edema. The lesion is characterized by a heterogeneous signal with prevalent hyperintensity on T2-FLAIR with regressive necrotic areas on post-contrast T1W with vivid peripheral ring enhancement. DCS-MRI shows hyperperfusion with high rCBV values. ¹HRS shows an elevation of the Cho peak with a high Cho/NAA ratio.