Male, 61 years old, history lung cancer, with brain tumor, preoperative evaluation. A very heterogeneous, lobular mass is evident centered on the left temporal lobe which spans the temporal stem to involve the thalamus and basal ganglia. The core of the lesion is composed of predominantly nonenhancing, cystic components with areas of smudgy low T2 signal likely representing either blood product or mineralization. Rim enhancement of the cystic components is seen with heterogeneous but relatively more solid enhancement along the inferior margin. Curvilinear internal enhancement is suggestive of vascularity. On some slices, the lesion appears to be contiguous with the choroid plexus. There may be subependymal enhancement along the left lateral ventricle.Extensive T2 hyperintensity surrounds the lesion extending into the adjacent white matter tracts. Substantial generalized mass effect is observed with a midline shift to the right of up to 12 mm, uncal herniation, shift of the brainstem to the right, effacement of and herniation into the left ambient cistern and prepontine cistern, and effacement of the left lateral ventricle. The left occipital horn is likely entrapped. The left cisternal trigeminal nerve appears stretched.The right lateral ventricle is not dilated. The third and fourth ventricles are within normal limits. No remote enhancing lesions are seen. A left cerebral subdural fluid collection is seen which follows CSF signal intensity on both T1 and T2-weighted images measuring up to 15 mm in thickness. Single and multi voxel spectroscopy was performed within and around the large left temporal lesion. The core of the lesion demonstrates prominent peaks related to both lipid and lactate indicating necrosis. The enhancing margin of the lesion shows variably reduced NAA and increased choline, though the choline increase is modest relative to levels obtained from normal-appearing parenchyma. The immediate perilesional tissues show no significant choline increase.
A very large heterogeneously enhancing tumor is present centered on the left temporal lobe with substantial associated mass effect as described above. The core of the lesion is largely cystic and necrotic with enhancing tissue seen predominantly along the periphery and the inferior margin. The lesion appears to be quite vascular. The differential diagnosis would include a high-grade primary brain tumor as well as a metastatic lesion. The appearance of the lesion on conventional images would favor a primary brain tumor. However, on spectroscopic assessment, lack of choline elevation in the lesion periphery is a feature often attributed to noninfiltrative lesions such as metastases.