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Definition:
Presence of lipid in higher concentration within a mass than in background reference tissue (e.g. liver).
Usage:
- Applies to masses that, in whole or in part, unequivocally have higher fat content than background liver.
- In patients at risk for HCC, intra-lesional fat is an ancillary feature favoring malignancy.
- Intra-lesional fat specifically favors HCC as opposed to malignancy in general
- Radiologists at their discretion may apply intra-lesional fat to upgrade category (up to LR-4).
- MRI is more sensitive and specific for detection of intra-lesional fat than CT
- At MRI, a mass may be characterized as having intra-lesional fat if:
- it shows signal loss on out-of-phase (OP) compared to in-phase (IP) gradient echo images or it shows signal loss on fat-suppressed compared to non-fat-suppressed images AND
- its degree of signal loss is greater than that of liver (i.e., it has higher fractional fat content than liver).
- At CT, a mass may be characterized as having intra-lesional fat if:
- its attenuation measures < 40 Hounsfield units (HU) on unenhanced images AND
- its attenuation is less than that of liver (i.e., it has higher fractional fat content than liver).
- Do not characterize as intra-lesional fat
Synonyms:
- Steatotic nodule, Fatty lesion
Potential pitfalls and challenges:
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