CT and MRI features of hepatic metastatic disease

CT and MRI features of hepatic metastatic disease

Hepatic metastasis is the most common malignant tumor of the liver and is about 20 times more common than HCC. It is more commonly seen in men than in women, usually in those who are >50 years of age.

Metastatic disease is suspected when an enhancing hepatic lesion is seen in a patient with a history of primary malignancy (unless cirrhosis is present, in which case HCC is more likely). In general, the liver is the second most common site of metastatic disease in the body (lymph nodes are the most common site). A hepatic metastasis can be hypervascular or hypovascular, depending on the nature of the primary tumor. The suspicion for metastatic disease is greater when lesions are multifocal, are heterogeneous but with similar enhancement patterns, have ill-defined margins, invade vascular structures, obstruct the biliary tree, grow over time, or are associated with direct perihepatic extension, regional lymphadenopathy, or extrahepatic metastatic disease.

On CT, hepatic metastases will vary in their attenuation and enhancement properties depending on their tissue composition and are often heterogeneous in appearance. Low attenuation components relative to liver parenchyma may be present secondary to presence of mucinous, myxoid, cystic, or necrotic tissue components (generally best visualized on venous phase images). Higher attenuation components relative to liver parenchyma may also be present secondary to hyperenhancing soft tissue components (generally best visualized on arterial phase images), calcification, hemorrhage, or increased tissue cellularity.

On MRI, hepatic metastases will similarly vary in signal intensity and enhancement properties depending on their tissue composition, and again are often heterogeneous. However, isointense T2-weighted signal intensity relative to spleen and restricted diffusion are additional highly suggestive findings that add specificity for the presence of metastatic disease.

Peripheral continuous rim enhancement is classically seen in hepatic metastases and should not be confused with the peripheral nodular discontinuous enhancement pattern of hepatic hemangiomas. However, the enhancement pattern of hepatic metastases can be variable, ranging from minimal to marked, as well as from homogeneous to heterogeneous. A “peripheral washout” sign may sometimes be seen on delayed phase images. It manifests as a peripheral rim of decreased enhancement relative to the lesion center and is more commonly present in hypervascular metastases. Hypointense signal intensity relative to liver parenchyma is also typically encountered on hepatobiliary phase images given the lack of retention of hepatobiliary contrast material.

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