What are the common MRI features to determine if a focal hepatic lesion is hepatocellular or extrahepatocellular in origin?
Determination of the origin of a focal hepatic lesion as hepatocellular or extrahepatocellular is useful to establish a definitive diagnosis for the lesion. Commonly encountered lesions of hepatocellular origin include FNH, hepatic adenoma, focal hepatic steatosis, regenerative nodule, and HCC.
In general, lesions that are isointense to hyperintense in signal intensity relative to liver parenchyma on in-phase T1-weighted images are hepatocellular in origin, whereas lesions that are low in signal intensity relative to liver parenchyma are generally extrahepatocellular in origin. Presence of intralesional lipid content, as manifested by a loss of signal intensity within a hepatocellular origin hepatic lesion on out-of-phase T1-weighted images relative to in-phase T1-weighted images, is often seen in all of the hepatocellular origin hepatic lesions listed above except for FNH but is not seen in most extrahepatocellular origin hepatic lesions with the exception of lipid-containing hepatic metastases from clear cell renal cell carcinoma or adrenocortical carcinoma. Retention of hepatobiliary MRI contrast material within a lesion during the hepatobiliary phase of enhancement generally indicates presence of either focal hepatic steatosis, regenerative nodule, or FNH, whereas all other hepatic lesions appear hypointense relative to surrounding liver parenchyma during this phase of enhancement. Lesions with high T2-weighted signal intensity relative to liver but intermediate signal intensity relative to spleen tend to be due to a malignant neoplasm, whereas lesions with high T2-weighted signal intensity relative to both liver and spleen parenchyma are most often due to cysts or hemangiomas.
MRI Features of Hepatic Lesions of Hepatocellular Origin
| LESION | T1-W | T2-W | HEAVILY T2-W | POSTCONTRAST T1-W | OTHER |
|---|---|---|---|---|---|
| Focal steatosis | = | = to ↑ | = | = on all phases | Often geographic in shape and in particular distribution, no mass effect upon vessels |
| FNH | =; ↓ of central scar | =; ↑ of central scar | = | ↑↑↑ on A phase; = on V, D, and HB phases; ↑ of central scar on D phase | Homogeneous enhancement, central scar, no lipid content |
| Hepatic adenoma | = to ↑; ↑↑ if hemorrhagic | = to ↑ | = | ↑↑ on A phase; = to ↓ on V and D phases; ↓ on HB phase | More heterogeneous, a/w oral contraceptive use |
| Regenerative nodule | = to ↑; ↓ if siderotic | = to ↓ | = | = on all phases | Small, multiple, in cirrhotic liver |
| HCC | = to ↓ | = to ↑ | = | ↑↑ on A phase; = to ↓ on V and D phases; ↓ on HB phase | More heterogeneous, often in cirrhotic liver, ± vascular invasion, ± metastatic disease |
Table legend: T1-W means T1-weighted; T2-W means T2-weighted; = means approximately isointense to liver parenchyma; ↑ means increased signal intensity relative to liver parenchyma; ↓ means decreased signal intensity relative to liver parenchyma; A means arterial; V means venous; D means delayed; HB means hepatobiliary; a/w means associated with.
MRI Features of Hepatic Lesions of Extrahepatocellular Origin
| LESION | T1-W | T2-W | HEAVILY T2-W | POSTCONTRAST T1-W | OTHER |
|---|---|---|---|---|---|
| Cyst | ↓↓↓; ↓↓ to ↑↑ if proteinaceous or hemorrhagic | ↑↑↑; ↓↓ to ↑↑ if proteinaceous or hemorrhagic | ↑↑↑; ↓↓ to ↑↑ if proteinaceous or hemorrhagic | No or minimal thin rim enhancement | |
| Hemangioma | ↓ | ↑↑↑ | ↑↑ | Peripheral nodular discontinuous enhancement on A phase; centripetal fill-in on V phase; persistent enhancement on D phase | Sometimes flash-filling in A phase when small in size; often central cleftlike area of cystic degeneration or liquefaction when large in size |
| Hepatic metastasis | ↓ | ↑ | = to ↑ | Variable, may have continuous rim enhancement, ± “peripheral washout” sign in V or D phase | History of primary tumor often known, often heterogeneous, usually multiple, ± extrahepatic metastatic disease, no cirrhosis present |
| Abscess | ↓↓; ↓↓↓ if contains foci of gas | ↑↑; ↓↓↓ if contains foci of gas | ↑; ↓↓↓ if contains foci of gas | Rim and septal enhancement in A or V phase that persists in D phase, regional hyperenhancement | Often clustered, may be surrounded by edema |
| Intrahepatic cholangiocarcinoma | ↓ | ↑ | = to ↑ | Heterogeneous peripheral enhancement in A and V phases with gradual centripetal fill-in on D phase | Heterogeneous, ± biliary obstruction, ± capsular retraction, ± extrahepatic metastatic disease |
| Hepatic lymphoma | ↓ | ↑ | = to ↑ | Hypoenhancing on all phases | Homogeneous, usually multiple, often associated with lymphadenopathy |
Table legend: T1-W means T1-weighted; T2-W means T2-weighted; = means approximately isointense to liver parenchyma; ↑ means increased signal intensity relative to liver parenchyma; ↓ means decreased signal intensity relative to liver parenchyma; A means arterial; V means venous; D means delayed.
