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Parenchymal Metastases
KEY FACTS
Terminology
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Secondary brain tumors (metastases) arise from
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Tumors outside CNS spreading to CNS (usually via hematogenous dissemination)
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Primary CNS neoplasms spreading from 1 site to another (usually geographic extension, e.g., along WM tracts)
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Imaging
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General features
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Round enhancing lesion(s) at gray-white interface (arterial border zones)
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Most metastases are circumscribed/discrete > > infiltrating, spherical > > linear
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50% are solitary; 20% have 2 metastases
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30% of patients have 3 or more
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MR signal intensity varies with
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Cellularity, nuclear:cytoplasmic ratio
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Presence/absence of hemorrhage
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Usually no restriction on DWI
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Exception: Densely cellular metastases may restrict
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Top Differential Diagnoses
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Abscess (solitary or multiple)
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Glioblastoma multiforme
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Cerebral infarction (multiple embolic)
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Demyelinating disease (e.g., tumefactive MS)
Pathology
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Metastases represent at least 50% of all brain tumors
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In 10% of cases, brain is only site
Clinical Issues
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Progressive increase in size and numbers is typical
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Median survival with whole-brain XRT = 3-6 months
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Stereotactic radiosurgery alone > whole-brain XRT
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Survival advantage, if 1-4 metastases, avoids deleterious effects of whole-brain XRT on quality of life, cognition
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Resection of solitary metastasis may improve survival
Axial graphic shows parenchymal metastases
with surrounding edema
. The gray-white matter junction is the most common location. Most metastases are round, not diffusely infiltrating.
with surrounding edema . The gray-white matter junction is the most common location. Most metastases are round, not diffusely infiltrating.
Close-up view of an axial section through an autopsied brain shows a classic metastasis
in the classic location, the gray-white matter junction. Note the round shape, central necrosis, and relative lack of edema. Diffuse leptomeningeal metastatic spread
is also present.
in the classic location, the gray-white matter junction. Note the round shape, central necrosis, and relative lack of edema. Diffuse leptomeningeal metastatic spread is also present.
Axial T2WI MR in a 52-year-old man with a seizure, history of melanoma, shows multiple lesions
at the gray-white matter interfaces. Moderate edema surrounds the lesions. One of the lesions has a hypointense nodule
, suggesting that at least 1 is a hemorrhagic metastasis.
at the gray-white matter interfaces. Moderate edema surrounds the lesions. One of the lesions has a hypointense nodule , suggesting that at least 1 is a hemorrhagic metastasis.
T1 C+ FS MR (same case) shows that the lesions enhance
. Note small metastasis
in the right ventricle choroid plexus that was not appreciated on T2WI. The extensive occipital edema is also from a metastasis (not seen on this image).
. Note small metastasis in the right ventricle choroid plexus that was not appreciated on T2WI. The extensive occipital edema is also from a metastasis (not seen on this image).
TERMINOLOGY
Abbreviations
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Parenchymal metastases (mets)
Synonyms
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Secondary brain tumors
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Body-to-brain metastases
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Brain-to-brain metastases
Definitions
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Secondary brain tumors (metastases) arise from
-
Tumors outside CNS that spread to CNS (usually via hematogenous dissemination)
-
Primary CNS neoplasms that spread from one site to another (usually geographic spread, e.g., along white matter [WM] tracts)
-
IMAGING
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