Metastases

Diagnosis
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  • Brain metastases are the most common malignant intracranial tumors in adults
  • Most are due to hematogenous dissemination
  • They are most commonly intraparenchymal in adults and skull/dural-based in children
  • The most common origins are lung cancer, followed by breast cancer, malignant melanoma, renal cell carcinoma, and colon cancer
  • Brain metastases vary in signal on MRI but are generally low signal on T1 and high signal on T2 and FLAIR sequences
  • Hemorrhage is indicated by blooming artifact seen on gradient echo (GRE) or susceptibility weighted imaging (SWI) sequences and is most commonly seen in melanoma, choriocarcinoma, renal cell carcinoma, thyroid cancer, and some types of bronchogenic carcinoma
  • Melanoma metastases can be hyperintense on T1 due to T1 shortening from melanin or hemorrhage
  • Surrounding edema and mass effect are common
  • Almost all metastases will enhance with contrast, which can appear solid or ring-like
  • Skull metastases are best seen on CT as sclerotic or lucent lesions and on MRI as infiltration and loss of normal T1 bright fat in the diploic space
  • Highly cellular metastases typically have restricted diffusion on diffusion-weighted MRI
  • Contrast-enhanced MRI detects 2-3 times as many metastases as contrast-enhanced CT, especially lesions that are less than 5 mm in diameter
  • Approximately 20% of patients with solitary metastatic lesions on CT show multiple lesions on MRI
  • Most brain metastases are multiple, but 30% of metastases are solitary and may be confused with primary brain tumors
  1. Barajas RF, Cha S. Metastasis in adult brain tumors. Neuroimaging Clin N Am 2016; 26(4):601-620
  2. Al-Okaili RN, Krejza J, Wang S, Woo JH, Melhem ER. Advanced MR imaging techniques in the diagnosis of intraaxial brain tumors in adults. RadioGraphics 2006; 26(Suppl 1):S173–89