MRI and MR spectroscopy of the tumor. (a) Axial T2-weighted image shows a sharply demarcated, hyperintense lesion on the posterior aspect of the left basal ganglia and the subcortical left parieto-insular lobe. The lesion affects the internal and external capsules without reaching the insular cortex. (b) Follow-up MR imaging after 1 year demonstrates progression of the lesion size, particularly on the posterior part, with medially located hyperintense foci corresponding to microcysts on T2-weighted imaging. (c) Coronal T1-weighted MR imaging after gadolinium administration shows punctual enhancement within the lesion. (d) Proton MR spectroscopy using a short echo time (TE: 30 ms) on the lateral part of the lesion reveals a reduced NAA peak and reduced lactate levels (1.3 ppm). The lactate concentration appears more prominent on the medial part of the lesion (and correlates with the microcystic, necrotic changes observed in Figure 1b), as shown on the metabolic map overlaid on the axial T2-weighted image (e).