How does HCA appear on US CT and MRI?
General: HCAs are more common in women and are associated with oral contraceptive use. HCAs can cause morbidity and mortality because of their propensity for hemorrhage and rare malignant degeneration to HCC. HCAs are often 8 to 15 cm in diameter when diagnosed. HCAs contain few if any bile ducts or Kupffer cells, but they are more likely to demonstrate calcification or fat than FNH.
US: Typically shows a heterogeneous, hyperechoic mass caused by internal hemorrhage and high lipid content.
MDCT: A hypodense mass is typically seen on NCCT resulting from intratumoral fat. Internal areas of higher attenuation may be present as a result of recent hemorrhage, a key distinguishing feature from FNH. Contrast-enhanced CT (CECT) may show centripetal enhancement similar to a hemangioma. In contrast to hemangiomas, the enhancement is transient.
MRI: HCA is commonly heterogeneous as a result of necrosis and internal hemorrhage. HCA is usually T2-w iso- to slightly hyperintense. The T1-w signal is variable, but often hyperintense because of fat or hemorrhage, although similar findings may be seen in HCC. HCA can demonstrate decreased signal on opposed-phase T1-w imaging because of the high lipid content. Enhancement is most pronounced in the HAP with rapid washout in the PVP. The presence of hemorrhage helps differentiate HCA from HCC.