BACKGROUND:

Poor differentiation and microvascular invasion are indicators of poor outcome after hepatectomy for patients with small hepatocellular carcinoma (HCC).

AIMS:

We investigated whether gadoxetic acid-enhanced and diffusion-weighted magnetic resonance imaging (MRI) could predict these factors before hepatectomy.

METHODS:

Between July 2008 and April 2012, 75 patients who underwent hepatectomy for small HCCs (diameter: ≤3cm, tumor number: ≤3) were consecutively enrolled. In gadoxetic acid-enhanced MRI, the signal intensity in the tumor was corrected to that in the paraspinous muscles, and the relative enhancement was calculated. In diffusion-weighted imaging, we measured the apparent diffusion coefficient (ADC). We then investigated the correlations between relative enhancement or ADC and histological grade, microvascular invasion and recurrence-free survival.

RESULTS:

Poorly differentiated HCCs showed significantly lower ADC than well-differentiated and moderately differentiated HCCs. There was no significant difference in the hepatobiliary phase. Only ADC was an independent predictor of microvascular invasion, and the best cut-off point of its prediction was 1.175×10(-3)mm(2)/s. Additionally, the recurrence-free survival was significantly shorter in low-ADC group than in high-ADC group.

CONCLUSION:

ADC is useful for predicting poorly differentiated HCCs and microvascular invasion, and low ADC is associated with increased recurrence risk for small HCCs after hepatectomy.