- Pathogenesis:
- A benign lesion but can be
pre-malignant. Pathologically, it consists of hepatocytes but lacks bile
ducts, portal tracts, or Kupffer cells. Fat and glycogen can
accumulate in these hepatocytes and may affect the lesion's appearance
on imaging. Adenoma may have pseudocapsule and central
scar. It can also hemorrhage, thrombose, and necrose.
- Most likely seen in young women.
- Associated with oral contraceptives and
steroids.
- May be seen with pregnancy, may enlarge
and has a tendency to bleed.
- Radiographic findings:
- Adenoma has a heterogeneous and variable
appearance secondary to fat and hemorrhage. FNH usually has homogeneous
enhancement in arterial phase and washes out promptly. This is a
characteristic that may help distinguish adenoma from FNH (Baron and
Federle, University of Pittsburgh).
- Noncontrast CT: equal attenuation or lower
attenuation with surrounding liver parenchyma if significant amount of
fat is present.
- Contrast CT: no marked enhancement, may
see hemorrhage.
- T1-weighted MRI: heterogeneous, with
areas of increased signal from both fat and hemorrhage. On in- and
out-of-phase imaging, a decrease in signal on the out-of-phase sequence
is seen if the lesion contains fat.
- T2-weighted MRI: heterogeneous, with
areas of increased signal.
- Nuclear medicine: does not take up
sulfur colloid due to absence of Kupffer cells.
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