H/O dragging of the RLE.
Past H/O breast carcinoma.
A large lesion which is isointense to hyperintense on all the pulse sequences is seen in the left, parafalcine, parietal region with presence of perilesional white matter edema. It shows intense peripheral enhancement(thick wall) on the post-contrast(Gd-chelate) images. Another smaller, similar lesion is noted in the right frontal lobe. A focal hyperintensity is noted in the right parietal lobe on the FLAIR images and a focal area of enhancement in the left frontal lobe.
Metastatic disease comprises approximately 20% of all detected brain tumors. In approximately 45% the primary source is not known. Common sources are bronchus(34.3%), breast(17.08%), digestive tract(6.24%), melanoma(6.05%), kidney(5.09%), others(12.4%) and unknown(18.9%).
They are usually distributed via the hematogenous route(early-at the grey/white matter junction-probably the result of narrowing of the vessels supplying the cortex). Calvarial/dural deposits may compress upon the brain. 80-85% are supratentorial and 35-50% are solitary. Patients usually present with headaches, seizures, hemiparesis, giddiness, visual problems and/or aphasia.
Microscopically, they usually recapitulate histological appearance of the primary source.However, atypical features are not rare. Usually they are circumscribed, but can be infiltrative with gliotic changes and perivascular invasion. The amount of edema is not proportional to the lesion size(vasogenic white matter edema).
On MRI: |
Variable signal pattern(depending on the cellularity). Cystic necrosis is near isointense to CSF. Hemorrhage(20%-commonly seen with choriocarcinoma, renal cell carcinoma or melanoma) or proteinaceous material would alter the signal characteristics.
Lesion can be easily separated from peritumoral edema (hyperintense on T2W images). Edema does not cross the corpus callosum or involve the cortex(Primary infiltrative malignancies may do so).
Enhancement may be solid/nodular or ring-like. Wall is invariably thick and shaggy/irregular. Benign pathologies(e.g. abscess or resolving hematoma) usually have thin and smooth wall enhancement. Peritumoral edema does not enhance(very rare).
Melanoma metastases may be hyperintense on the T1W images and isointense to hypointense on the T2W images(melanin). Mucinous adenocarcinoma(e.g. colon) may be hypointense on the T2W images
Cortical lesions may be missed on non-enhanced scans.
| Differential Diagnosis: |
| MULTIPLE ENHANCING LESIONS WITH PERITUMORAL EDEMA |
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| SOLITARY-THICK RING ENHANCING LESION (SUPRATENTORIAL) |
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| SOLITARY MASS IN THE POSTERIOR FOSSA |
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