FAQ-079: Is there a minimum size for application of APHE, “washout”, and “capsule”?
No. It suffices that the presence of these features be definite in the judgment of the radiologist.
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FAQ-080: On what plane should I measure observation size?
For standardization, favor the axial plane. However, you may measure on a different plane on which margins are undistorted and well visualized. Use the same plane on future exams to assess growth.
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FAQ-081: Does washout appearance apply only to observations with APHE?
No, “washout” may apply even in the absence of APHE, as long as there is some enhancement.
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FAQ-082: Do washout appearance and APHE need to coincide in the same part of an observation?
No, APHE and washout appearance do not need to coincide in the same part. For example, a 25 mm mass with APHE in one part and “washout” in another part may be categorized LR-5.
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FAQ-083: Why does “washout” require comparison to composite liver tissue rather than nodules?
Historically, the literature in this field has assessed observation "washout" relative to the background liver —which we interpret as composite liver parenchyma— rather than nodules in particular. Until an alternative comparator is shown to be superior, we will preserve the current approach.
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FAQ-084: Why can’t I evaluate “washout” in the transitional phase when performing gadoxetate-MRI?
With gadoxetate-MRI, portal venous phase “washout” is relatively specific for HCC. However, transitional phase hypointensity lacks specificity because background liver uptake of the contrast agent is sufficiently high that cholangiocarcinomas and other non-HCC malignancies may appear hypointense.
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FAQ-085: Why does LI-RADS make a distinction between features that favor malignancy in general vs. features that favor HCC in particular?
Most features favoring malignancy are nonspecific, occurring in HCC and non-HCC. However, some features are specific for HCC and may help differentiate HCC from non-HCC.
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FAQ-086: If liver enhancement during the HBP is suboptimal, how do I characterize observations that are hypointense, isointense, or hyperintense relative to liver?
If an observation is hypointense in the hepatobiliary phase, it may be characterized as such despite suboptimal hepatobiliary phase parenchymal enhancement. However, if an observation is isointense or hyperintense, characterization of hepatobiliary phase intensity may be unreliable.
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FAQ-087: LR-M criteria seem most applicable to iCCA. What about other non-HCC malignancies?
LR-M criteria were formulated based on limited available evidence, most of which concerns HCC vs. iCCA differentiation. There is not yet sufficient evidence to formulate criteria for other non-HCC malignancies (primary or secondary). Fortunately, other malignancies are rare.
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FAQ-088: How do I differentiate HCC, cholangiocarcinoma, and hepatocholangiocarcinoma?
Some imaging features indicate hepatocellular origin (see below). The presence of such features excludes malignancies of non-hepatocellular origin such intrahepatic cholangiocarcinoma (iCCA) but they do not exclude combined hepatocellular carcinoma-cholangiocarcinoma (cHCC-CCA), which contain both hepatocellular and cholangiocellular elements. Implication: for malignant masses with hepatocellular features, the differential diagnosis is HCC and cHCC-CCA; differentiation of HCC from cHCC-CCA may not be possible.
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FAQ-089: What features suggest hepatocellular origin?
Fat in mass, blood products in mass, nodule-in-nodule, mosaic architecture, intrinsic T1 hyperintensity, HBP isointensity or hyperintensity, enhancing or nonenhancing “capsule”.
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FAQ-090: Why does growth apply only to masses?
Conceptually, growth refers to enlargement of a mass by spreading or expansion. Nonmass lesions like focal fat deposition may enlarge due to deposition of fat in adjacent hepatocytes but this does not represent spreading or expansion of the previously steatotic hepatocytes. More importantly, this provision preserves specificity for HCC by preventing attribution of growth to nonmass benign processes such as arterial perfusion alterations which may appear larger on one exam than on a prior due to changes in arterial phase timing or other factors. The provision that growth only applies to masses prevents false categorization of these benign vascular pseudolesions as LR-5.
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FAQ-091: How can I differentiate an arterial phase hyperenhancing mass with threshold growth from a benign vascular pseudolesion that appears larger on one exam than on a prior?
Features that favor mass over a vascular pseudolesion include visibility on other phases and/or sequences and mass effect (e.g., contour abnormality; displacement or distortion of vessels or ducts). Features that favor a vascular pseudolesion include occultness on all other phases and sequences, peripheral location, geographic or wedge shape (on source or multiplanar reformatted images), and absence of mass effect.
MRI with a hepatobiliary agent can help differentiate an arterial phase hyperenhancing mass from a vascular pseudolesion. The former tends to be distinctive from background liver in the hepatobiliary phase due to differences in signal intensity, texture, or other features. The latter tends to be occult.
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FAQ-092: If a mass met the threshold growth criterion previously but not on the current exam compared to the most recent prior exam(s), is threshold growth present or absent?
If a mass meets the threshold growth criterion at any point, threshold growth is characterized as present on all subsequent exams. Rationale: growth rates of malignant tumors may fluctuate and therefore may not meet the threshold growth criterion on every examination.