Ultrasound appearances of hepatic metastases

Ultrasound appearance of hepatic metastases can have bewildering variation, and the presence of hepatic steatosis can affect the sonographic appearance of liver lesions.

Radiographic features

Ultrasound

Patterns do exist between ultrasound appearance of the hepatic metastases and the likely primary, which is sometimes helpful in directing a search for an unknown primary, as well as helping distinguish between benign lesions and metastatic disease from a particular primary:

• hypoechoic: most common ~65%
  • lung cancer
  • breast cancer
  • pancreatic adenocarcinoma
  • lymphoma
• hyperechoic
  • colorectal carcinoma (CRC)
  • renal cell carcinoma (RCC)
  • choriocarcinoma
  • Kaposi sarcoma
  • neuroendocrine tumors
    • carcinoid
    • pancreatic islet cell tumors
• peripheral halo: a hypoechoic halo is a concerning feature, sometimes called the target or bull's eye lesion/sign
  • common in many
  • lung cancer
• calcified
  • mucinous adenocarcinoma
    • gastrointestinal
    • ovarian mucinous adenocarcinoma
• cystic
  • squamous cell carcinoma
  • ovarian cancer
  • pancreatic adenocarcinoma
  • colorectal carcinoma (CRC)
• poorly defined (infiltrative)
  • melanoma
  • breast cancer
  • lung cancer
• associated intrahepatic biliary dilation
  • colorectal carcinoma (CRC)

Contrast-enhanced ultrasound

Contrast-enhanced ultrasound may be useful to increase the conspicuity of lesions and/or guide biopsy.

The 'hypovascular' and 'hypervascular' terminology refers to metastatic appearance on contrast-enhanced cross-sectional studies as peak arterial enhancement is not necessarily seen on arterial phase. The viable metastases of the liver show at least early peripheral enhancement on contrast-enhanced ultrasound even if the central aspect would remain unenhanced (necrotic). The extension of the central necrotic area often correlates the tumor size, hence small gastrointestinal metastases may enhance avidly and homogeneously in arterial phase.

• arterial phase: variable depending on primary
  • hypovascular:  gastrointestinal, ovarian, pancreatic adenocarcinoma
  • hypervascular: neuroendocrine, melanoma, renal
• portal venous and late phase
  • "wash out" (decreased echogenicity relative to background liver due to the lack of enhancement); may be the most useful phase for detection as all of the liver metastases show this phenomenon