Presentation
Seizure and loss of consciousness.
Patient Data
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Large multilobulated cystic mass within the left frontal lobe showing thin capsular enhancement ("ring enhancement") and causing prominent local mass effect with vasogenic edema and subfalcine herniation.
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Large left frontal lobe multilobulated cystic lesion showing an internal high T2 signal that partially suppresses on FLAIR and has thin enhancing margins. There is a small posterior septated lobulation that has restricted diffusion but that otherwise has the same signal pattern of the core lesion; other small foci of diffusion restriction are noted within the enhancing rim at the medial margins of the lesion. The tumor causes a noticeable mass effect with surrounding vasogenic edema, subfalcine herniation and rightward midline shift in about 2 cm. No uncal or tonsillar herniation. Areas of elevated cerebral blood volume (CBV) at parts of the margin. The cortex appears to be spared on the T2 axial images, with no definitive evidence of cortical thickening. No convincing choline elevation along the lesion margins on spectroscopy. Although these findings suggest metastasis, presence of increased T2/FLAIR signal involving the genu of the corpus callosum would be more in keeping with glioma. Right frontal lobe area of encephalomalacia is probably sequela of a previous infarct.

Para mediastinal right lower lobe mass associated with a more peripheral ill-defined air space opacification and reticular markers in the same lobe. The remainder of the lungs and pleural spaces are clear.
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Mass within the superior segment of the right lower lobe likely represents a primary lung cancer. The smaller lesion within the lateral segment of the right middle lobe may represent a second primary or alternatively a metastatic focus. Intralobular septal thickening at the right base raises the possibility of lymphangitis carcinomatosis. Alternatively, post-obstructive infection could also have a similar appearance. Extensive mediastinal nodal metastases involving the right hilum, subcarinal, right paratracheal and prevascular nodal stations.
Case Discussion
The patient was submitted to a resection of the brain lesion; histology confirmed it to be metastatic lung cancer. The case is a good example of how to approach a ring-enhancing cerebral mass and the difficulties that sometimes occur when trying to differentiate between high-grade glioma and metastasis.
MICROSCOPIC DESCRIPTION: Paraffin sections show discrete islands of a densely hypercellular tumor within brain parenchyma. These are composed of epithelioid cells in which a prominent peripheral basaloid type cell layer differentiates centrally into squamous epithelial cells. Foci of keratinization are discernible as well as intercellular bridges. Frequent mitotic figures are identified. All tumor islands show extensive central necrosis imparting a pseudo-cystic appearance. The features are of metastatic poorly differentiated squamous cell carcinoma and are most consistent with an origin from lung.
DIAGNOSIS: "Left frontal brain lesion": Metastatic poorly differentiated squamous cell carcinoma with features most consistent with an origin from lung.