Table 2 Summary of MRI features of major subtypes of hepatocellular adenoma (HCA) and focal nodular hyperplasia (FNH)
| Â | Subtype | T1W | T2W | In and out of phase | Arterial | Portal venous/delayed | Remarks |
|---|---|---|---|---|---|---|---|
Focal nodular hyperplasia | Classic | Iso- to mildly hypointense | Iso- to mildly hyperintense | No signal drop | Intense enhancement | Persistent enhancement | T2 hyperintense scar showing delayed enhancement |
Non-classic | Heterogeneous hypo- or iso- or hyperintense | Heterogeneous iso- or hyperintense | Focal signal drop rarely | Intense heterogeneous enhancement | Heterogeneous persistent enhancement with pseudocapsule | Absent or atypical scar | |
Hepatocellular adenoma | Inflammatory HCA | Iso- to mildly hyperintense | Diffusely hyperintense | No diffuse signal drop | Intense enhancement | Persistent enhancement | Atoll sign-T2 hyperintense rim. 10Â % can have focal intratumoral fat |
HNF1a-mutated HCA | Iso- to hyperintense | Iso- to mildly hyperintense | Diffuse signal drop | Moderate enhancement | No persistent enhancement | Â | |
ß-catenin-mutated HCA | Isointense | Iso-, hypo- or hyperintense | No diffuse signal drop | Intense | Variable. May show portal venous washout | Faint scar and ill-defined T2 hyperintense foci | |
Unclassified | – | – | – | – | – |  |